Specifications for Soil Nail Anchors - PDF

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					                                               Recommended Guidelines for
                                                  Permanent Soil Nails
1. SOIL NAIL ASSEMBLIES................................................................................................................ 44

2. CONTRACT DRAWINGS................................................................................................................. 44
     2.1 SUBMITTALS ........................................................................................................................................ 44
3.0 MATERIALS..................................................................................................................................... 44
     3.1 REINFORCING STEEL........................................................................................................................... 55
        3.1.2. Solid Reinforcing Steel bar that conforms to ASTM A615 (grade 60 & 75) and ASTM A722
        (grade 150). ....................................................................................................................................... 55
        3.1.3. Self-Drilling Hollow Core Bar................................................................................................ 55
     3.2. CORROSION PROTECTION OF THE SOIL NAIL ASSEMBLY...................................................................... 55
        3.2.1 Solid Reinforcing Steel Bar ...................................................................................................... 55
           A. Epoxy Coating .......................................................................................................................... 55
           B. Hot Dip Galvanizing................................................................................................................. 55
           C. Encapsulated with cement grout in corrugated plastic sheathing. ............................................ 66
        3.2.2. Self-Drilling Hollow Core Bar................................................................................................ 76
     3.3 BEARING PLATE ................................................................................................................................. 77
     3.4 HEX NUT ............................................................................................................................................ 77
     3.5 BEVELED WASHERS ........................................................................................................................... 77
     3.6 SPLICE COUPLER \ .............................................................................................................................. 77
     3.7 CENTRALIZERS ................................................................................................................................... 88
4. CONSTRUCTION AND DRILLING ............................................................................................... 88
     4.1 SELF-DRILLING HOLLOW CORE BAR .................................................................................................... 88
     4.2 SOLID THREADED REINFORCING STEEL ............................................................................................... 88
5. TRANSPORTATION AND HANDLING PROCEDURES ............................................................ 99

6. GROUTING..................................................................................................................................... 1010

7. SECURING SOIL NAILS .............................................................................................................. 1111

8. TESTING ......................................................................................................................................... 1111
     8.1 NAIL TESTING ............................................................................................................................ 1212
     8.2 TESTING EQUIPMENT .............................................................................................................. 1212
     8.3 VERIFICATION TESTING.......................................................................................................... 1313
     8.4 PROOF TESTING ........................................................................................................................ 1615
     8.5 TEST NAIL ACCEPTANCE........................................................................................................ 1817
     8.6 TEST NAIL REJECTION............................................................................................................. 1918
     8.7 SITE MONITORING .................................................................................................................... 2019
9.      MEASUREMENT ....................................................................................................................... 2019
Recommended Guidelines for Permanent Soil Nails                                                                                 Page 2 of 4746
10. PAYMENT..................................................................................................................................... 2120

A. STEEL PROPERTIES................................................................................................................... 2221
   A.1 REINFORCING STEEL PROPERTIES ASTM A615 (GRADE 60 & 75) ............................................... 2221
   A.2 PRESTRESSING STEEL PROPERTIES ASTM A-722 ......................................................................... 2221
   A.3 SELF-DRILLING HOLLOW CORE BAR PROPERTIES ......................................................................... 2322
     A.3.1 MAI bar type ........................................................................................................................ 2322
     A.3.2 CTS/TITAN bar type ............................................................................................................ 2322
B. CORROSION: CAUSES - PREVENTION AND PROTECTION METHODS ...................... 2423
   B.1 CORROSION ................................................................................................................................... 2423
     B1.1      General.......................................................................................................................... 2423
     B.1.2       Aggressivity of the Environment................................................................................... 2423
     B.1.3     Basic electrochemical corrosion cell ............................................................................ 2524
     B.1.4     Steel in concrete ............................................................................................................ 2524
     B.1.5     Factors affecting cell activity ........................................................................................ 2524
     B.1.6     Different corrosion phenomena..................................................................................... 2625
        B.1.6.1 Uniform corrosion ..................................................................................................... 2625
        B.1.6.2 Localized corrosion/Pitting corrosion ....................................................................... 2625
        B.1.6.3 Crevice corrosion ...................................................................................................... 2625
        B.1.6.4 Stress corrosion cracking (SCC) ............................................................................... 2625
        B.1.6.5 Hydrogen embrittlement............................................................................................ 2625
        B.1.6.6 Corrosion fatigue....................................................................................................... 2726
        B.1.6.7 Fretting corrosion ...................................................................................................... 2726
        B.1.6.8 Stray current corrosion .............................................................................................. 2726
        B.1.6.9 Corrosion in soil. Microbiological corrosion ............................................................ 2726
   B.2 CORROSION PROTECTION - POSSIBLE METHODS.............................................................................. 2827
     B.2.1     General.......................................................................................................................... 2827
     B.2.2     Requirements of corrosion protection........................................................................... 2827
        B.2.3.1 Hot dip galvanizing ................................................................................................... 2827
        B.2.3.2.    Fusion bonded epoxy coated-................................................................................ 2928
        B.2.3.3.    Multiple corrosion protection with cement grout and corrugated plastic sheathing.
                    2928
   B.3. CONCLUSION ................................................................................................................................ 3030
C. PERMANENT SHOTCRETE FACING AND WALL DRAINAGE ........................................ 3231
   C.1.0 DESCRIPTION ......................................................................................................................... 3231
     C.1.1 Contractor's ......................................................................................................................... 3231
     C.1.2 Construction Submittals ...................................................................................................... 3332
     C.1.3 Pre-Construction Meeting ................................................................................................... 3433
   C.2.0 MATERIALS................................................................................................................................. 3433
     C.2.1 Shotcrete Mix Design........................................................................................................... 3635
        C.2.1.1 Aggregate...................................................................................................................... 3635
        C.2.1.2 Proportioning and Use of Admixtures.......................................................................... 3635
        C.2.1.3 Air Entrainment ............................................................................................................ 3635
Recommended Guidelines for Permanent Soil Nails                                                                               Page 3 of 4746
        C.2.1.4 Strength and Durability Requirements. ........................................................................ 3736
        C.2.1.5 Mixing and Batching. ................................................................................................... 3736
      C.2.2 Field Quality Control. ......................................................................................................... 3736
        C.2.2.1 Preconstruction Test Panels.......................................................................................... 3736
        C.2.2.2 Production Test Panels. ................................................................................................ 3837
        C.2.2.3 Test Panel Curing, Test Specimen Extraction and Testing. ......................................... 3837
   C.3.0 CONSTRUCTION REQUIREMENTS..................................................................................... 3938
      C.3.1 Wall Drainage Network....................................................................................................... 3938
        C.3.1.1 Geocomposite Drain Strips........................................................................................... 3938
        C.3.1.2 Footing Drains. ............................................................................................................. 3938
        C.3.1.3 Connection Pipes and Weepholes................................................................................. 3938
      C.3.2 Permanent Shotcrete Facing ............................................................................................... 4039
        C.3.2.1 Shotcrete Alignment and Thickness Control................................................................ 4039
        C.3.2.2 Surface Preparation....................................................................................................... 4039
        C.3.2.3 Delivery and Application.............................................................................................. 4039
        C.3.2.4 Defective Shotcrete....................................................................................................... 4140
        C.3.2.5 Construction Joints. ...................................................................................................... 4140
        C.3.2.6 Final Face Finish........................................................................................................... 4241
        C.3.2.7 Attachment of Nail Head Bearing Plate and Nut.......................................................... 4241
        C.3.2.8 Weather Limitations. .................................................................................................... 4241
        C.3.2.9 Curing. .......................................................................................................................... 4241
      C.3.3 Backfilling Behind Wall Facing Upper Cantilever. ............................................................ 4342
      C.3.4 Safety Requirements............................................................................................................. 4443
   C.4.0 METHOD OF MEASUREMENT............................................................................................. 4443
   5.0 BASIS OF PAYMENT ........................................................................................................................ 4443
COMMENTARY TO PERMANENT SHOTCRETE FACING AND WALL DRAINAGE GUIDE
SPECIFICATION ............................................................................................................................... 4544
   C.1.1 EXPERIENCE REQUIREMENTS ........................................................................................... 4544
   C.2.1. SHOTCRETE MIX DESIGN................................................................................................... 4544
   C.2.2 FIELD QUALITY CONTROL.................................................................................................. 4645
   C.3.1 WALL DRAINAGE NETWORK ............................................................................................. 4645
   C.3.2 PERMANENT SHOTCRETE FACING................................................................................... 4645
Recommended Guidelines for Permanent Soil Nails             Page 4 of 4746

1. SOIL NAIL ASSEMBLIES
Soil nail assemblies and test soil nail assemblies,
consist of installing and grouting steel bars in holes
drilled in any type of natural ground. Anchorage sys-
tem, and testing of test soil nail assemblies, shall
conform to the details shown on the plans and these
special provisions.

2. CONTRACT DRAWINGS
Contract drawings shall show the location, procedure
and layout of the soil nail installation. This includes
the pattern, spacing, type, size and lengths of the
nails, as well as, the required drill hole diameter,
embedment depths, and the angled inclination of the
soil nails. The drawings shall also indicate other de-
tails such as anchor plate size, any additional re-
quired corrosion protection for the nail and its com-
ponents, minimum concrete cover over the bar and
the end of the nail, spacing of centralizers, and test
nail details, if required.

2.1 Submittals
Prior to starting the work, shop drawings when nec-
essary, as well as, related data such as catalog cuts,
product details, and brochures, shall be submitted to
the Engineer for review.

3.0 MATERIALS
Soil nails shall preferably be furnished complete with
all accessories, and shall be a standard product of a
company regularly engaged in their manufacture.
Where this is not the case, all soil nail components
shall be designed by a licensed Engineer and con-
form to all design standards for the purpose for
which they are intended. When required, a certifi-
cate of compliance and copies of the certified mill
report of the soil nail steel, will verify that the nails
conform to requirements of this specification. The
materials specified below shall be used for construc-
tion of soil nail assemblies and test soil nail assem-
blies.
Recommended Guidelines for Permanent Soil Nails         Page 5 of 4746
3.1 Reinforcing Steel
used for soil nail assembly shall be either:

3.1.2. Solid Reinforcing Steel bar that conforms
to ASTM A615 (Grade 60 & 75) [Grade 420 & 520]
and ASTM A722 (150 ksi) [Grade 1035].
Bars will have a continuous rolled-in pattern of
thread-like deformations along their entire length or
can be rolled thread for a minimum 6 inches on the
anchorage and splice end. Cutting of the threads
onto the steel bar will not be allowed. For technical
data on “Reinforcing Steel Properties ASTM A615”
(Grade 60 & 75) [Grade 420 & 520] and “Prestress-
ing Steel Properties ASTM A722” (150 ksi) [Grade
1035], see appendix A.

3.1.3. Self-Drilling Hollow Core Bar
This is a high-grade hollow core steel bar with con-
tinuous threaded surface for mechanical coupling,
supplied in various lengths. Soil nail assembly shall
be lengthened in the field as required by the shop
drawing details. For technical data on Hollow Core
Bars, see appendix A.

3.2. Corrosion protection of the soil nail assem-
bly

3.2.1 Solid Reinforcing Steel Bar
can be corrosion protected by one or more of the fol-
lowing materials:

A. EPOXY COATING
shall conform to one of the following: ASTM A-934,
ASTM A-775, or AASHTO No. M 284.

B. HOT DIP GALVANIZING
conforming to ASTM A-153 and AASHTO No. M
232.
Note: System components such as hex nuts, bevel
washers, couplings, and bearing plates may also be
epoxy coated or hot dip galvanized when required or
Recommended Guidelines for Permanent Soil Nails             Page 6 of 4746
may be uncoated where sufficient concrete cover is
provided.

C. ENCAPSULATED WITH CEMENT GROUT IN
CORRUGATED PLASTIC SHEATHING.
In order to provide a strict quality control, encapsula-
tion with cement grout inside corrugated plastic
sheathing will be done only at the plant location of
the soil nail manufacturer. Bars are centered and
encapsulated inside corrugated PVC or HDPE
sheathing and the annular space between bar and
sheathing is cement grouted. The corrugated plastic
sheathing insures a minimum 0.2 inches (5 mm)
grout cover over the solid reinforcing steel. Two
methods can be used:
•   Corrugated plastic sheathing fully encapsulates
    entire bar embedment length
•   Bar is epoxy-coated or hot-dip galvanized and
    only 3ft (1m) of bar length under bearing plate is
    encapsulated.
The corrugated plastic sheathing provides a rigid
mechanical lock between the factory-installed grout
and the field-applied grout.
If couplers are used, they will be field installed with a
double or multiple corrosion protection (DCP or
MCP) system as per manufacturer instructions or as
shown in the shop drawings.
Corrugated plastic sheathing shall be either polyvinyl
chloride (PVC) or high density polyethylene (HDPE).
The nominal sheathing wall thickness shall be 40
mils. The material will conform to ASTM D-3350
polyethylene, Index No. 335520 C, Table 1, ASTM
D-1248, and AASHTO No. M252 for HDPE or ASTM
D-1784 Class 13464-B for PVC. Diameter of the
corrugated sheathing is as noted on the shop draw-
ings.
The sheathing shall have sufficient strength to pre-
vent damage during construction operations, shall be
watertight, chemically stable without embrittlement
softening, and nonreactive with concrete.
Recommended Guidelines for Permanent Soil Nails             Page 7 of 4746
3.2.2. Self-Drilling Hollow Core Bar
can be zinc-metallized, or hot dip galvanized con-
forming to ASTM A-153 or epoxy coated in accor-
dance with ASTM A934 or ASTM A775. Thread ends
will be cleaned to allow hex nut and coupler thread-
ability.

3.3 Bearing Plate
shall be made from steel conforming to ASTM A-
36/A36M. The dimensions shall be as shown on the
contract drawings.
Bearing plate shall have an oversized round or slot-
ted center hole sufficient for the required soil nail in-
clination angle. Additional holes for grout tubes when
required shall be provided in the plate as applicable.
Four steel concrete anchor studs will be butt welded
to the bearing plate at each corner. Their material,
diameter, length and location shall be as shown on
the contract drawings.

3.4 Hex Nut
shall be heavy duty, hexagonal type as per manufac-
turer’s standard specifications. The hex nut will be
tapped oversize when additional corrosion protection
of epoxy coating or hot dip galvanizing is specified.
The hex nut shall be capable of developing 100% of
the guaranteed ultimate tensile strength of the bars.
(spherical anchor nuts do not require beveled wash-
ers)

3.5 Beveled Washers
will be used to provide angular adjustment. Two
bevel washers shall be capable of rotating against
each other until reinforcing steel is perpendicular to
the bearing surface of the hex nut. Bevel washer
shall be made from steel or malleable iron.

3.6 Splice Coupler
when required, may be used to splice the soil nails
and shall be capable of developing 100% of the
guaranteed ultimate tensile strength of the bars. The
couplings will be tapped oversize when additional
Recommended Guidelines for Permanent Soil Nails             Page 8 of 4746
corrosion protection of epoxy coating or hot dip gal-
vanizing is specified. (Couplings for self drilling bars
shall be provided with a center stop)
Hex nut, bearing plate and beveled washer can be
epoxy coated or hot dip galvanized or adequately
covered by concrete, shotcrete or grout.

3.7 Centralizers
shall be installed as noted on the contract drawings,
along the length of the soil nail to insure that the soil
nail will be centered in the drill hole and that mini-
mum grout cover encapsulates the rebar. Centraliz-
ers shall be manufactured from polyvinyl chloride
(PVC)

4. CONSTRUCTION AND DRILLING
Construction process should generally start from the
top down by excavating approximately five feet of
soil at a slope equal to the final batter of the wall.
The first row of soil nails can be installed by, either
method 4.1. or 4.2. Alternate construction methods
will be considered provided the methods meet the
intent of the design and are verification tested prior
to production.

4.1 Self-drilling hollow core bar
Drilling and preparing of cement grout is performed
simultaneously allowing soil nail installation and
grouting in a single operation. Drill bit used must al-
low cutting through different type of soil conditions.
Drill bits shall be provided with venturi holes to allow
for proper tremie grouting. Centralizers are not used
with self-drilling hollow core bar.

4.2 Solid threaded reinforcing steel
Holes are drilled and soil nail assemblies are in-
stalled using centralizers. Centralizers shall ade-
quately support the bar in the center of the drilled
hole and shall be spaced at a maximum of 10 feet
(3 m) on center.
Recommended Guidelines for Permanent Soil Nails            Page 9 of 4746
Drilling equipment shall be designed to drill straight
and of sufficient diameter to provide 1 inch (25 mm)
of grout cover over the nail. The size and capability
of the drilling equipment shall be determined by the
contractor. Methods of drilling will be determined by
the contractor. Where caving conditions are speci-
fied elsewhere in these special provisions, sufficient
casing and auger lengths shall be available on site to
maintain uninterrupted installation of anchors. If the
contractor proposes and the Engineer approves, hol-
low core self-drilling bar with adequate corrosion pro-
tection can be used at the locations where ground
caving is expected to occur.
Variations in nail locations can be up to 24 in.
(600mm) and variation in nail angle of +/-5 degrees
without re-design. The Engineer will suspend wall
construction if subsidence or other detrimental im-
pact from drilling occurs.
Holes for soil nail assemblies and for test soil nail
assemblies shall be the same diameter and utilize
the same installation techniques, including grout.
Casing may be used to stabilize the holes, but shall
be removed prior to or during the grouting operation.
For self drilling bars, casing is not required.
Holes shall be cleaned to remove material resulting
from the drilling operations and to remove any other
material that would impair the strength of the soil nail
assemblies or test soil nail assemblies. Foreign ma-
terial dislodged or drawn into the holes during con-
struction of the assemblies shall be removed.

5. TRANSPORTATION AND HANDLING
PROCEDURES
Soil Nails encapsulated with corrugated plastic
sheathing and pre-grouted, are normally shipped ly-
ing horizontal in bundles with multiple banding points
to help prevent bending of the nails that could cause
cracking of the internal grout layer. The use of mul-
tiple pickup points (a spreader beam is recom-
mended for the purpose) is required to decrease the
possibility of cantilever deflections and sagging be-
tween pickup points during transportation load-
Recommended Guidelines for Permanent Soil Nails              Page 10 of 4746
ing/unloading operations, movements to installation
sites and insertion into prepared anchorage holes.
Neither soil nails that are shipped in bundles nor as
individual nails should be dropped, dragged, or
pulled off a transportation vehicle.
If field cutting is required, the exposed threaded sec-
tion of the steel bars will be cut with a portable band
saw or an abrasive cutoff wheel which will not gener-
ate overheating of the area of the soil nails where
internal threaded tension components are intended
for use. The use of a cutting torch is prohibited.
When the soil nails have been epoxy coated or hot
dip galvanized, the exposed end of the soil nail that
has been field cut can be repaired with an approved
epoxy patch kit or zinc spray from the manufacturer.
Welding to either the steel bars or to the internal
threaded components is not allowed. The soil nails
should not be used as grounding for electric welding
apparatus.
Soil nails that have been severely bent, nicked, cut,
compressed (flattened in the thread section down to
the minor diameter) or nails that are worn out due to
other uses, misuse, or have external threads cor-
roded with permanent pitting should be inspected to
determine if strength capacities are diminished.
Also, if the soil nails have been previously tensioned
beyond their rated yield strength, they should be dis-
carded.

6. GROUTING
When using threaded reinforcing steel, the length of
drilled hole shall be monitored by the Inspector be-
fore and during grouting.
When using self-drilling hollow core bars, grouting
shall be done continuously during the drilling opera-
tion through a rotary injection adapter attached to the
end of the anchor. Grout will flow through the hollow
core hole exiting through the drill bit holes.
In case of the solid reinforcing steel, grout shall be
injected at the low end of the drilled hole. The grout
shall fill the entire drilled hole with a dense grout free
Recommended Guidelines for Permanent Soil Nails               Page 11 of 4746
of voids or inclusion of foreign material. When self-
drilling hollow core bar is used, ground cuts can be
mixed with cement grout.
Soil nails shall be grouted full length.
For test soil nails, only the bonded length shall be
initially grouted. Grouting of the remainder of the
drilled hole shall not be done until after completing
pullout tests.
Cold joints shall not be used in grout placement, ex-
cept for test soil nails.
After placing the grout for soil nails and test soil
nails, they shall remain undisturbed for the cure time
stated in the approved soil nail working drawings.
Only clear, potable water, free of oil, acid, alkali, or-
ganic matter, or injurious quantities of chlorides, fluo-
rides, sulfates and nitrates will be used when mixing
with Portland cement.
Use cement grout with a water/cement ratio as rec-
ommended by the manufacturer. Fine aggregate
can be added but only to the extent that cement con-
tent of the grout is not less than 846 pounds per cu-
bic yard of grout.

7. SECURING SOIL NAILS
Any remaining void at the exterior end of the drilled
hole for a soil nail assembly shall be filled with shot-
crete and the soil nail secured at the face of the
shotcrete. The steel bearing plate shall be seated
with full bearing on the shotcrete surface and the nut
for the soil nail shall be tightened before the initial set
of the shotcrete. The nut shall be made wrench tight
after the shotcrete has set for 24 hours, unless the
Engineer approves a shorter time. Reinforcing in-
side shotcrete will be as specified by contract docu-
ments.

8. TESTING
A percentage of soil nail assemblies shall be tested
and will be referred to as test soil nails. Testing shall
be performed against a temporary bearing yoke,
Recommended Guidelines for Permanent Soil Nails           Page 12 of 4746
which bears directly on the shotcrete facing or exca-
vated face cut. Test loads transmitted through the
temporary bearing yoke shall not fracture the shot-
crete or cause displacement or sloughing of the soil
surrounding the drilled hole. At a minimum, the total
number of test nails should be 5% of the total num-
ber of production nails. For test nails, the grout body
shall not be in contact with the shotcrete.

8.1 NAIL TESTING
Both verification and proof testing of the nails shall
be required. The Contractor shall supply all material,
equipment, and labor to perform the tests. Owner’s
Inspector shall measure, and record all required data
in an acceptable manner. Testing or stressing of
nails shall not be performed until the grout has
reached sufficient strength to ensure design bond
stresses can be mobilized (typically 24 to 48 hrs).

8.2 TESTING EQUIPMENT
Testing Equipment shall include, at a minimum, a
dial gauge, a dial gauge support, jack and pressure
gauge, and a reaction frame.
Soil nail movement shall be monitored by the use of
dial gauges capable of measuring to 0.001 inch
(0.025 mm). The dial gauges shall have a minimum
stroke equal to the theoretical elastic elongation of
the total nail length plus 1 inch (25 mm). The dial
gauges shall be aligned within 5 degrees from the
axis of the nail. A hydraulic jack and pump shall be
used to apply the test load.
The jack and pressure gauge shall be calibrated by
an independent testing laboratory as a unit. The
pressure gauge shall be graduated in 100 psi
increments or less and shall have a range not less
than twice the anticipated maximum pressure during
testing unless otherwise approved by the Engineer.
The pressure gauge shall be used to measure the
applied load. The minimum ram travel of the jack
shall not be less than the theoretical elastic
elongation of the total nail length at the maximum
Recommended Guidelines for Permanent Soil Nails            Page 13 of 4746
test load plus 1 inch (25 mm). The jack shall be
capable of applying each load in less than 1 minute.
The jack shall be independently supported and
centered over the nail so that the nail does not carry
the weight of the jack. The loads on the nails during
the verification tests shall be monitored with a
pressure gauge. The Contractor shall provide a
recent (within 60 days) calibration curve in
accordance with submittals.           The stressing
equipment shall be placed over the nail in such a
manner that the jack, bearing plates, load cell, and
stressing anchorage are in alignment. The jack shall
be positioned at the beginning of the test such that
unloading and repositioning of the jack during the
test will not be required.
The reaction frame shall be sufficiently rigid and of
adequate     dimension     such      that   excessive
deformation of the test apparatus requiring
repositioning of any components shall be avoided.
Where the reaction frame bears directly on the
shotcrete, the reaction frame shall be designed to
preclude fracture of the shotcrete. No part of the
reaction frame shall bear within 6 inches (150 mm) of
the edge of the test nail blockout unless otherwise
approved by the Engineer.

8.3 VERIFICATION TESTING
Verification testing shall be performed prior to or
during production nail installation to verify the
installation methods, soil conditions, and nail
capacity. The details of the verification testing
arrangement including the method of distributing test
load pressures to the excavation surface (reaction
frame), nail bar size, grouted hole diameter and
reaction plate dimensioning, shall be developed and
submitted by the Contractor. All nail testing shall be
made using the same equipment, methods, and hole
diameter as planned for the production nails.
Changes in the drilling or installation method may
require additional verification testing as determined
by the Engineer. The nails used for the verification
tests shall be sacrificial and shall not be incorporated
into the production nail schedule.
       Recommended Guidelines for Permanent Soil Nails            Page 14 of 4746
       At least two verification nails shall be installed.
       Successful verification tests are required prior to
       production nail installation. The locations of the
       verification tests shall be determined by the
       Contractor and approved by the Engineer.
       Test nails shall have both bonded and unbonded
       portions. Prior to testing only the bonded length of
       the test nail shall be grouted. The unbonded length
       of the test nail shall be at least 3 feet (1 m) unless
       otherwise approved by the Engineer. The bonded
       length shall be determined by the Engineer based on
       the bar grade and size and installation method
       provided by the Contractor such that the allowable
       bar load is not exceeded. The bonded length shall
       not be less than indicated above. The maximum bar
       load during testing shall not be greater than 80
       percent of the ultimate strength of the steel for 150
       ksi (Grade 1035) bars nor greater than 90 percent of
       the yield strength for grade 60 and 75 (Grade 420
       and 520) bars and self-drilling hollow core bars.
       The maximum verification test bonded length LBV
       shall not exceed the test allowable bar load divided
       by 2 times the design adhesion value, as shown in
       the following equations:
                 CFyA s
       L BV ≤                  for grade 60 and 75 (Grade 420
                  2 AD
                               and 520) bars, and self-drilling
                               hollow core bars


               CFu As
       LBV ≤                for 150 ksi (Grade 1035) bars
                2 AD


Where: LBv = Maximum Test Nail Bond Length (ft) [m]

                 Fy     =      Bar Yield Stress (ksi) [kN/m2]
                               for grade 60 and 75 (Grade 420
                               and 520) bars, and self-drilling
                               hollow core bars
Recommended Guidelines for Permanent Soil Nails            Page 15 of 4746
           Fu   =     Bar Ultimate Stress (ksi) [kN/m2]
                      for 150 ksi (Grade 1035) bars


       As       =     Bar Area (in2) [m2]

AD               =    Design Adhesion (kips/foot)
                [kN/m] as shown on the plans

       C         =      0.8 for 150 ksi (Grade 1035)
                bars and 0.9 for Grade 60 and 75
                (Grade 420 and 520) bars, and self-
                drilling hollow core bars


The design load during verification testing shall be
determined by the following equation:
            DL = LB x AD
Where: DL = Design load (kips) [kN]
       LB = As-built bonded length (ft) [m]
       AD = Design adhesion (specified herein as
            kips/ft) [kN/m]
Verification test nails shall be incrementally loaded to
twice the design load (DL) and movements recorded
by the Contractor in accordance with the following
schedule.
     VERIFICATION TEST LOADING SCHEDULE


                 AL         1 minute
                 0.25DL     1 minute
                 0.50DL     1 minute
                 0.75DL     1 minute
                 1.00DL     1 minute
                 1.25DL     1 minute
                 1.50DL     10 minutes
                 1.75DL     10 minutes
                 2.00DL     10 minutes
Where AL = Alignment Load
Recommended Guidelines for Permanent Soil Nails          Page 16 of 4746
The alignment load (AL) should be the minimum load
required to align the testing apparatus and should
not exceed 5 percent of the Design Load (DL). Dial
gauges should be set to “zero” after the alignment
load has been applied.
Each load increment shall be held for at least 1
minute. The verification test nail shall be monitored
for creep at the 1.50 DL load increment. Nail
movements during the creep portion of the test shall
be measured and recorded at 1 minute, 2, 3, 5, 6,
and 10 minutes. Extended creep measurements
may be required and shall be monitored as
determined by Engineer. All load increments shall
be maintained within 5 percent of the intended load.
Upon successful completion of the verification test,
the nail shall be loaded in 25 percent increments
until stable reading is obtained to no more than
allowable bar load (CFyAs) for grade 60 & 75 (Grade
420 and 520) , and self-drilling hollow core bars, and
(CFuAs) for 150 ksi (Grade 1035) bars to determine
the ultimate pullout capacity.

8.4 PROOF TESTING
Proof testing shall be performed on at least 5
percent of the production nails in each shotcrete lift
to verify the Contractor's methods and the design
nail capacity. The locations and number of these
tests shall be determined by the Contractor.
Alternatively, the contractor may install 3 percent
additional verification test nails in lieu of the 5
percent proof testing on production nails.
Proof test nails shall have both bonded and
unbonded portions. Prior to testing only the bonded
length of the test nail shall be grouted. Owner’s
Inspector shall determine the bonded and unbonded
lengths of the test nail. The unbonded length of the
test nail shall be at least 3 feet (1m). The bonded
length of the test nail shall be determined by the
Engineer such that the allowable bar load is not
exceeded. The allowable bar load shall not exceed
90 percent of the yield strength for grade 60 and 75
(Grade 420 and 520) , and self-drilling hollow core
      Recommended Guidelines for Permanent Soil Nails                 Page 17 of 4746
      bars nor be greater than 80 percent of the ultimate
      strength of the steel for 150 ksi (Grade 1035) bars.
      The maximum proof test bonded length LBP shall not
      exceed the allowable bar load divided by 1.5 times
      the design adhesion values, as shown in the
      following equations:
                CF y As
       LB P ≤                 for grade 60 and 75 (Grade 420 and
                1.5 AD
                                520) bars, and self-drilling hollow
                                core bars




                CFu As
       LB P ≤                 for 150 ksi (Grade 1035) bars
                1.5 A D


Where: LBP      = Maximum Test Nail Bond Length (ft) [m]

                  Fy      =      Bar Yield Stress (ksi) [kN/m2]
                                 for grade 60 & 75 bars (Grade
                                 420 and 520) bars, and self-
                                 drilling hollow core bars


                  Fu      =      Bar Ultimate Stress (ksi) [kN/m2]
                                 for 150 ksi (Grade 1035) bars


                  As      =      Bar Area (in2) [m2]

                  AD       =    Design Adhesion (kips/foot)
                          [kN/m] as shown on the plans

                    C     =       0.8 for 150 ksi (Grade 1035)
                           bars and 0.9 for Grade 60 and 75
                           (Grade 420 and 520) bars, and self-
                           drilling hollow core bars
      Proof tests shall be performed by incrementally load-
      ing the nail to 150 percent of the design load. The
Recommended Guidelines for Permanent Soil Nails          Page 18 of 4746
design load shall be determined as for verification
test nails. The nail movement at each load shall be
measured and recorded by Owner’s Inspector in the
same manner as for verification tests. The load shall
be monitored by a pressure gauge with sensitivity
and range meeting the requirements of pressure
gauges used for verification test nails. At load in-
crements other than maximum test load, the load
shall be held long enough to obtain a stable reading.
Incremental loading for proof tests shall be in accor-
dance with the following schedule.
          AL
          0.25DL
          0.50DL
          0.75DL
          1.00DL
          1.50DL
          AL = Nail Alignment Load
          DL = Nail Design Load
All load increments shall be maintained within 5
percent of the intended load.         Depending on
performance, either 10 minute or 60 minute creep
tests shall be performed at the maximum test load.
The creep period shall start as soon as the maximum
test load is applied and the nail movement with
respect to a fixed reference shall be measured and
recorded at 1 minute, 2, 3, 5, 6, and 10 minutes.
Where nail movement between 1 minute and 10
minutes exceeds 0.04 inch (1mm), the maximum test
load shall be maintained an additional 50 minutes
and movements shall be recorded at 20 minutes, 30,
50, and 60 minutes.

8.5 TEST NAIL ACCEPTANCE
A test nail shall be considered acceptable when:
1.   For verification tests, a creep rate less than
     0.08 inch (2mm) per log cycle of time is
     observed during creep testing and the rate is
     linear or decreasing throughout the load hold.
2.   For proof tests where less than 0.04 inches
     (1mm) of movement is observed between the 1
Recommended Guidelines for Permanent Soil Nails           Page 19 of 4746
     minute and 10 minute interval during the 10
     minute creep test or a creep rate less than 0.08
     inch (2mm) per log cycle of time is observed
     during the 60 minute creep test and the creep
     rate is linear or decreasing throughout the load
     hold period.
3.   The total movement at the maximum test load
     exceeds 80 percent of the theoretical elastic
     elongation of the unbonded length.
4.   The maximum test load is sustained without
     reaching the failure point (pullout). The failure
     point shall be the point where the movement of
     the test soil nail continues without an increase
     in the load. The failure load corresponding to
     the failure point shall be recorded as part of the
     test data.
Proof test nails may be incorporated into the
production nail schedule provided that (1) the
unbonded length of the nail hole has not collapsed
during testing, (2) the minimum required hole
diameter has been maintained, and (3) the test nail
length is equal to or greater than the scheduled
production nail. Test nails meeting these
requirements shall be completed by grouting the
unbonded length. Maintaining the unbonded length
for subsequent grouting is the Contractors
responsibility. If the unbonded length of production
test nails cannot be grouted subsequent to testing
due to caving conditions or other reasons, the
Contractor shall replace the test nail with a similar
production nail at his cost and to the satisfaction of
Engineer.

8.6 TEST NAIL REJECTION
Engineer may require that the Contractor replace
some or all of the installed production nails between
the failed test and the adjacent passing proof test
nail.    Alternatively, Engineer may require that
additional proof testing be conducted based on the
results of the nail tests.
Recommended Guidelines for Permanent Soil Nails            Page 20 of 4746
8.7 SITE MONITORING
Prior to any construction activities that may affect
adjacent properties, a complete existing condition
survey should be undertaken to observe and
document the preconstruction condition of all
structures, infrastructure, sidewalks, roadways, and
all other facilities adjacent to the site. Documentation
shall be circulated to Contractor, Engineer and
Owner prior to the start of excavation.
During the excavation phase the soil nail wall shall
be inspected daily by visual observation for signs of
ground or building movements in the vicinity of each
working front. In addition, temporary monitoring
points in the upper five feet of the wall should be
established to enable survey monitoring of lateral
wall deflections and wall crest settlement to be
undertaken.    Monitoring points should be at a
maximum horizontal spacing of 40 ft (12m). Survey
points shall be monitored no less than once per
week during excavation and twice a month there
after until the permanent wall is completed.
Monitoring reports should be circulated to contractor,
Engineer and owner within 24 hrs of data collection.
The Engineer may choose to monitor particular
structures or areas more frequently using crack
monitoring devices, or additional temporary
benchmarks.

9. MEASUREMENT
Soil nail assembly and test soil nail assembly will be
measured and paid for by the linear foot. The length
to be paid for will be the length of soil nail assembly
or test soil nail assembly measured along the bar
centerline from the back face of shotcrete to the tip
end shown on the plans or ordered in writing by the
Engineer.
Shotcrete will be measured on the basis of the
square footage applied measured in the plane of the
wall.
Alternately a combined payment for soil nail assem-
bly and shotcrete may be used based upon the
Recommended Guidelines for Permanent Soil Nails          Page 21 of 4746
square footage of shotcrete applied measured in the
plane of the wall.

10. PAYMENT
The contract price paid, typically on the basis of the
square footage of permanent wall constructed
measured in the plane of the wall, shall include full
compensation for furnishing all labor, materials,
tools, equipment, and incidentals, and for doing all
the work involved in constructing the permanent wall,
complete in place, as shown on the plans, as speci-
fied in the Standard Specifications and these special
provisions, and as directed by the Engineer.
Full compensation for testing of the soil nail assem-
blies shown on the plans shall be considered as in-
cluded in the contract price unless a separate unit
price for testing is provided.
Appendix to the Recommended Guidelines for Permanent Soil Nails                                        Page 22 of 4746


Appendices

A. STEEL PROPERTIES

A.1 Reinforcing Steel Properties ASTM A615 (Grade 60 & 75)
Grade     Threadbar      Yield               Cross Sec-             Yield           Nominal            Max. Threadbar
         Designation     Stress              tional Area          Strength          Weight                Diameter
         in-lb. mm     ksi Mpa               in2     mm2         kips    kN      lbs/lf kg/m             in      mm

  60       #6     19     60         414       .44     284        26.4      118   1.50         2.24          0.86   21.8

  60       #7     22     60         414      0.60     387        36.0      160   2.04         3.04          0.99   25.1

  60       #8     25     60         414      0.79     510        47.4      211   2.67         3.98          1.12   28.4

  75       #6     19     75         517      0.44     284        33.0      147   1.50         2.24          0.86   21.8

  75       #7     22     75         517      0.60     387        45.0      200   2.04         3.04          0.99   25.1

  75       #8     25     75         517      0.79     510        59.3      264   2.67         3.98          1.12   28.4

  75       #9     29     75         517      1.00     645        75.0      334   3.40         5.06          1.26   32.0

  75      #10     32     75         517      1.27     819        95.3      424   4.30         6.41          1.43   36.3

  75      #11     36     75         517      1.56    1006        117.      520   5.31         7.91          1.61   40.9
                                                                    0
  75      #14     43     75         517      2.25    1452        168.      751   7.65    11.39              1.86   47.2
                                                                    8

A.2 Prestressing Steel Properties ASTM A-722
 Grade      Nominal       Cross Sec-                Ultimate            Weight          Max Bar Di-
          Bar Diameter     tion Area                Strength                             ameter



           in     mm          in2     mm2      kips         KN      lbs/ft    kg/m       in          mm
  150       1     26      0.85        548      127.5      567       3.01      4.48      1.20         30.5

  150     1 1/4   32      1.25        806      187.5      834       4.39      6.54      1.46         37.1

  150     1 3/8   36      1.58        1018      237      1055       5.56      8.28      1.63         41.4

  150     1 3/4   46      2.66        1716      400      1779       9.23      13.74     2.00         51.0
Appendix to the Recommended Guidelines for Permanent Soil Nails                Page 23 of 4746



A.3 Self-Drilling Hollow Core Bar Properties

A.3.1 MAI bar type
           BAR               UNIT               MAI BAR TYPE
      DESCRIPTION                     R25N R32N R32S R38N R51L R51N
OUTER DIAMETER                 in       1     1 1/4   1 1/4   1 1/2    2      2
CROSS SECTIONAL AREA         sq. in. 0.47      0.67   0.78    1.16    1.40   1.63
YIELD LOAD                    kips     34      52      63      90     101    142
ULTIMATE LOAD                 kips     45      63      81     112     112    180
WEIGHT                       lbs/ft    1.75    2.42   2.82    4.00    5.00   5.40

A.3.2 CTS/TITAN bar type
           BAR               UNIT              CTS/TITAN BAR
                                                   TYPE
      DESCRIPTION                     30/16 R32/20 30/11 40/20 40/16 52/26
OUTER DIAMETER                 in     1.06    1.25    1.19    1.56    1.56   2.06
CROSS SECTIONAL AREA         sq. in. 0.592    0.69    0.69    1.00    1.36   2.08
YIELD LOAD                    kips    40.5    52.0    58.4    97.0    118.1 160.8
ULTIMATE LOAD                 kips    49.5    58.0    72.0    115.0 148.4 209.0
WEIGHT                       lbs/ft 1.02      2.30    2.35    3.60    4.64   7.14
Appendix to the Recommended Guidelines for Permanent Soil Nails                   Page 24 of 4746

B. CORROSION: CAUSES - PREVENTION AND PROTECTION METHODS

B.1 Corrosion

B1.1 General
Corrosion is the term used to designate the deterioration of a metal by chemical or
electrochemical reaction with its environment. Most commonly used metals are produced by
extraction from their oxides. Therefore, the refined metal is in a thermodynamically less stable
state than that of its natural oxide form and under appropriate conditions will revert to oxides,
i.e. it corrodes. When corrosion inhibiting constraints are lacking the metal will react with oxygen
and water to form oxides and/or hydroxides. The process by which corrosion occurs is generally
recognized to be electrochemical in nature, i.e. a galvanic cell is developed. The term galvanic
corrosion is used, in a broad sense, to denote corrosion occurring from dissimilar adjacent
surface conditions of a metal, differences in oxygen concentrations or differences in
environmental conditions.

B.1.2 Aggressivity of the Environment
Test and/or field observations are used to classify the aggressivity of the environment.
Ground shall be considered aggressive if it has one or more of the following, a pH value less
than 4.5, a resistivity less than 2000 ohm-cm, sulfides present, stray currents present or has
caused chemical attack to other buried concrete structures. In addition, aggressive atmos-
pheric conditions need to be considered.
If the aggressivity of the ground has not been determined by testing, then aggressive conditions
are assumed in:
Soils with a low pH
Salt water or tidal marshes
Cinder, ash or slag fills
Organic fills containing humic acid
Peat bogs
Acid mine or industrial waste.
Aggressivity of the ground is influenced by:
Resistivity of the soil,
pH value of the soil,
Chemical composition of the ground water and the soil or rock,
Water and air permeability of the ground,
Groundwater elevation (stable or fluctuating) and
External electrochemical and physical factors (long-line and stray-current corrosion systems).
Appendix to the Recommended Guidelines for Permanent Soil Nails                   Page 25 of 4746
B.1.3 Basic electrochemical corrosion cell
Three basic constituent parts form an electrolytic cell: an anode, a cathode and an electrolyte.
To form a corrosion cell the anode and the cathode must be connected metallically, i.e.
electrons can move between anode and cathode. The term anode is used to denote the
location at which the metal corrodes. At this location the metal atom gives up electrons in a
reaction with the corroding medium. The free electrons are consumed at the cathode by oxygen
reduction. These two reactions are coupled by a migration of ions into the electrolyte at the
anode and discharged at the cathode. Further, corrosion cannot occur without a potential
difference producing a current flow between the anode and the cathode (corrosion current).
This potential difference may occur e.g. through differential oxygen concentration (different
aeration) of the concrete surrounding the steel. Parts of the steel in a well aerated concrete
form cathodic areas and those portions of low oxygen concentration form anodic areas.

B.1.4 Steel in concrete
The concrete/cementitious mortar provides the steel with a physical barrier and a chemical
protection. Due to this physical barrier the access of corrosion promoting agents (carbon
dioxide, oxygen and humidity from the air, chlorides from deicing salt or other agents coming
into contact with the concrete) will be slowed down. The efficiency of this physical barrier
depends on the permeability of the concrete and the thickness of the concrete cover. The
influence of cracks can be neglected, until the crack width becomes greater than some
empirical value. The chemical protection function of concrete is due to its characteristic
alkalinity and the property of steel to create a tight nonconducting oxide film on its surface in an
alkaline environment. This phenomenon is known as passivation because the steel remains
passive against its environment. As long as the pH-value is within a range of 12.5 to 14 and the
Cl--ion content is below a certain threshold level, the steel surface is passivated, no corrosion
can occur.
Differences in the physical characteristics of the concrete (e.g. permeability) and/or its
environmental conditions (aeration, humidity) and chemical changes in the concrete
(carbonation, access of chlorides) can lead to changes of the steel surface such that the
passive film on it will be destroyed. When this happens, iron ions can escape the iron crystal-
lattice and go into solution with moisture in the concrete resulting in steel corrosion..

B.1.5 Factors affecting cell activity
The rate of corrosion is related to the ratio of the anodic region to the cathodic region.
Increasing this ratio by decreasing the cathodic area results in a reduced current flow which
denotes a decrease in the corrosion rate. Increasing the cathodic area (or decreasing the
anodic area) decreases this ratio resulting in an increased corrosion rate.
When passivation occurs it reduces the corrosion rate to a very low level or completely halts the
corrosion process. Obviously, when ions are present that destroy the passivation film the
corrosion rate will be greatly accelerated.
Appendix to the Recommended Guidelines for Permanent Soil Nails                  Page 26 of 4746
The electrical conductivity of the electrolyte (the concrete) is an important parameter in the rate
of corrosion, the higher the conductivity the greater the rate of corrosion. Conductivity is a
function of temperature, moisture and ionic content, since the corrosion current flows through
the electrolyte by ionic conduction.

B.1.6 Different corrosion phenomena
Categorization by the manner in which the steel is affected is discussed in this section.

B.1.6.1 UNIFORM CORROSION
If an approximately uniform surface attack of steel occurs, it implies that no discrete anodic and
cathodic sites exist. The corrosion products form a continuous film and thus may retard further
corrosion. This type of corrosion can develop when unprotected steel is exposed to the
environment, as during shipping, storage or prior to concreting/grouting.

B.1.6.2 LOCALIZED CORROSION/PITTING CORROSION
Due to nonhomogeneity of the metal surface and/or the corrosive environment separate
electrochemical cells may develop and localized corrosion can occur. As the ratio of anodic
area to cathodic area is very small, a locally high corrosion rate occurs which may lead to a
sudden brittle failure after a negligible loss of material. Localized corrosion occurs at locations
where the metal surface passivation has been destroyed or damaged. In the presence of
aggressive ions, such as chlorides, a pitting mechanism may occur.

B.1.6.3 CREVICE CORROSION
The mechanism of crevice corrosion is similar to that of pitting corrosion. Crevices can originate
from rolling defects or at close contact of the steel to an other impervious body, e.g. under nuts.
Here in the poorly aerated region anodic processes occur resulting in a brittle type of failure.

B.1.6.4 STRESS CORROSION CRACKING (SCC)
SCC is a type of locally concentrated corrosion defined as cracking that may result from the
combined action of corrosion and static tensile stress, which may be either residual or
externally applied. SCC occurs mainly in alloys where a passivated oxide film on the surface
has developed. The attack of the corrosion agent (mostly chloride ions) concentrate on certain
sensitive regions of the steel such as cracks or spalls.

B.1.6.5 HYDROGEN EMBRITTLEMENT
Cracking due to hydrogen embrittlement of steel under stress occurs when atomic hydrogen
diffuses through the metal lattice, where they recombine to hydrogen molecules producing an
internal pressure in the metal. Absorption of atomic hydrogen by the prestressing steel usually
occurs by cathodic charges, which develop in a corrosive environment when steel is electrically
coupled to more anodic metal, e.g., zinc coating. The atomic hydrogen may be formed by the
corrosion process itself or as a result of some manufacturing operations, e.g., pickling or
welding. Cracking of the steel can either be a direct consequence of the tensile stresses
Appendix to the Recommended Guidelines for Permanent Soil Nails                 Page 27 of 4746
developed by the hydrogen molecules within the metal lattice during their formation from two
hydrogen atoms or in combination with tensile stresses. It should be mentioned that different
steel types are differently susceptible to hydrogen embrittlement.

B.1.6.6 CORROSION FATIGUE
Corrosion fatigue is the result of the combined effect of corrosion and cyclic stresses. Cyclic
stresses may cause more rapid failures when accompanied by corrosion than static stresses of
the same magnitude. As both, fatigue and corrosion can reduce the life of prestressing steel,
their combined effect is the most detrimental when the life under the influence of the cyclic
stresses is further reduced by corrosive influences.

B.1.6.7 FRETTING CORROSION
Fretting is a surface wear phenomenon occuring when two contacting surfaces are subjected to
oscillating relative motion of small amplitude. Fretting corrosion is a form of fretting in which
chemical reaction predominates. Fretting corrosion may occur between a prestressing wire and
the metal duct/sheathing or between wires in a strand, especially where the direction of the
prestressing tendon changes.

B.1.6.8 STRAY CURRENT CORROSION
Structures which may be affected from stray current corrosion are those associated with electric
substations, electrified rail or tramway systems, or which are in contact with structures where a
very large amount of welding occurs. Alternating current electricity is much less likely to cause
severe corrosion unless it is of low frequency (approx. 17 Hz). The development of stray current
can be suppressed with a proper electrical insulation of the structure or a good metallic contact
of the steel components of the structure with the source of the stray current.

B.1.6.9 CORROSION IN SOIL. MICROBIOLOGICAL CORROSION
Soil as a corrosive medium can be regarded as a porous substance consisting of more or less
solid, partly colloidal, soluble and hygroscopic constituents and living organisms. The pores of
the soil contain air and water. Above the ground-water level the finest capillary tubes are filled
with water whereas the greater pores contain air. For corrosion in soils to occur, a certain mois-
ture is necessary and, generally oxygen. Nevertheless, steel can corrode under anaerobic con-
ditions as well. The most common form of microbiological attack comes from the metabolic
processes of sulfate reducing bacteria (SRB). The waste product of SRB metabolism are sul-
fide ions, which react with the metal allowing dissolution of the anodic region of the corrosion
cell to result in metal sulfide.
Appendix to the Recommended Guidelines for Permanent Soil Nails                      Page 28 of 4746
B.2 Corrosion protection - possible methods

B.2.1 General
Corrosion protection can be achieved when one or more reactions of the corrosion cell are pre-
vented: the anodic, the cathodic or the electrolytic. This means, that no humidity and/or no oxy-
gen and/or no carbon dioxide and/or no chloride ions may arrive at the steel surface.
Objective of the Engineer: Redundant, reliable and durable corrosion protection system

B.2.2 Requirements of corrosion protection
The corrosion protection elements and systems must meet some fundamental requirements:
-   no adverse effect on the strength and/or ductility of the structural elements
-   compatibility to each other with respect to their physical and chemical characteristics
-   resistance to the possible influences during service, e.g. mechanical, thermal, UV-radiation
-   no adverse effect to the environment
-   durability for the required life or replaceability without jeopardizing the stability and durability
    of the structure
-   practical and easy applicability
-   controllability
-   economical during construction and maintenance
-   particular requirements to special characteristics, e.g. bond to steel and concrete.
The grout encapsulation protection system is an excellent example of a good combination: the
plastic sheathing is a good humidity and oxygen barrier, i.e. proper passive protection, the ce-
mentitious grout provides alkaline, i.e. active protection, both, sheathing and grout provide also
mechanical protection to the steel.
B.2.3 Corrosion protection methods

B.2.3.1 HOT DIP GALVANIZING
Steel anchor components should be hot dip galvanized as per ASTM A-153(AASHTO M232).
Zinc is a well known, common and relatively inexpensive coating material for iron and steel.
Zinc acts as a sacrificial anode, i.e. it corrodes in a corrosive environment and lets the steel
play the role of cathode. The high alkalinity of concrete and grout (pH > 12) dissolves the zinc to
a certain extent, at pH < 12 a very low corrosion rate of zinc occurs due to the development of a
passivation film on the zinc surface. This film will stabilize if atmospheric CO2 reaches the
surface of zinc coating. This is the reason for the known durability of zinc coatings under open-
air conditions. However, it should be remembered that the zinc coating is a sacrificial coating,
hence its lifetime depends on the agressiveness of the environment and the thickness of the
coating applied. Zinc coating is quite ineffective if Chloride- or Sulphate ions beyond a threshold
level are present: local pitting corrosion occurs. When the zinc coating is damaged the cathodic
partial reaction related to the corrosion of zinc (i.e. development of hydrogen-atoms) primarily
occurs on the free steel surface due to the electrochemical characteristics of the zinc-iron
„battery“. The hydrogen atoms can partially be absorbed by the steel, causing hydrogen-
Appendix to the Recommended Guidelines for Permanent Soil Nails                Page 29 of 4746
embrittlement of steel types which are susceptible to this phenomenon. The rate of hydrogen-
development decreases during hardening of the fresh cement paste around the galvanized
steel in a matter of hours due to the development of a passive film on the zinc coating. Thus,
the risk of hydrogen-embrittlement vanishes within a few hours or days.

B.2.3.2 FUSION BONDED EPOXY COATED
Epoxy Coating shall conform to one of the following: ASTM A-934, ASTM A-775, or AASHTO
No. M 284.

B.2.3.3 MULTIPLE CORROSION PROTECTION WITH CEMENT GROUT AND CORRU-
GATED PLASTIC SHEATHING.
Steel is centered and fully encapsulated inside corrugated PVC or HDPE sheathing and annular
space between bar and sheathing will be shop cement grouted.
The sheathing shall have sufficient strength to prevent damage during construction operations,
shall be watertight, chemically stable without embrittlement softening, and nonreactive with
concrete.

B.2.3.3.A CORRUGATED PLASTIC SHEATHING
The ground anchor encapsulation shall be fabricated from material with the following properties:


Capable of transferring stresses from the grout surrounding the tendon to the grout in bond
length


Able to accommodate movements during testing and after lock-off

Resistant to chemical attack from aggressive environments


Resistant to aging by ultra-violent light


Non-detrimental to the tendon

Capable of withstanding abrasion, impact and bending during handling and installation

Capable of resisting internal grouting pressures


Steel bars are centered and fully encapsulated inside corrugated PVC or HDPE sheathing and
annular space between bar and sheathing will be shop cement grouted. The corrugated plastic
Appendix to the Recommended Guidelines for Permanent Soil Nails                     Page 30 of 4746
sheathing insures a minimum 5mm (0.2 inch) grout cover encapsulating the rebar steel either
over the entire bond zone or in a specified outer length (often a one meter length, under the
bearing plate in the active failure plane zone) to maximize corrosion protection in especially ag-
gressive soil conditions. The corrugated plastic sheathing provides a rigid mechanical lock be-
tween the factory-installed grout and the field-applied grout.
If steel bar couplers are used, they shall be field installed with a double or multiple corrosion
protection (DCP or MCP) system as per manufacturer instructions or as shown in the shop
drawings.
Corrugated plastic sheathing shall be either polyvinyl chloride (PVC) or high density polyethyl-
ene (HDPE). The minimum sheathing wall thickness shall be 40 mils. . The material will con-
form to ASTM D-3350 polyethylene, Index No. 335520 C, Table 1, ASTM D-1248, and
AASHTO No. M252 for HDPE or ASTM D-1784 Class 13464-B for PVC. Diameter of the cor-
rugated sheathing is as noted on the shop drawings.



B.2.3.3.B CEMENT GROUT
Inside the annular space between steel and corrugated sheathing is the most efficient element
of corrosion protection. It must provide proper alkalinity, low permeability, high resistivity, mini-
mum to no shrinkage in both plastic and hardened states, proper fluidity, little or no segregation
and no bleeding.
The grout mix used for rock and soil anchors shall be stable (bleed less than 2 percent), fluid
and provide a strength of at least 21 Mpa (3000 psi) at time of stressing. The type of cement
that is selected for grout that will be in contact with the ground shall take into account the known
or possible presence of aggressive substances. Soil samples may be necessary to evaluate
the aggressivity of the soil.
Grout cube testing is not normally required, but may be utilized to evaluate the time of anchor
stressing and the quality of the grout mix. Insufficient cube strength shall not be caused for re-
jecting a successfully tested anchor. A neat cement grout made with a W/C ratio of 0.40 to 0.45
by weight and Type I cement, mixed in a colloidal mixer, will normally satisfy these require-
ments.
If significant grout pressures are used in cohesionless soils, mix water will be squeezed out of
the grout as it attempts to travel through the soil (pressure filtration). This results in an in-place
grout with a lower water cement ratio than for the grout that was initially injected.
For this reason, water cement ratios as high as 0.55 can be used in cohesionless soils, if the
effective grout pressures exceed 0.4 Mpa (50 psi). In situ grout may be weakened, if the grout
is cured at low temperatures or when the grout has been diluted with groundwater.

B.3. Conclusion
A proper protection of the ordinary reinforcing steel and the prestressing steel against corrosion
is a great challange for engineers. A lot of knowledge is available, however it must be properly
Appendix to the Recommended Guidelines for Permanent Soil Nails           Page 31 of 4746
applied. Advanced corrosion protection methods and advanced corrosion protection systems
such as a double corrosion protection system can be applied to produce structures with the
required durability.
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C. PERMANENT SHOTCRETE FACING AND WALL DRAINAGE

                                           Taken from
                                FHWA GUIDE SPECIFICATION
                                          FOR
                                    (OWNER-DESIGN)



C.1.0 DESCRIPTION
Shotcrete facing and wall drainage work consists of furnishing all materials and labor required
for placing and securing geocomposite drainage material, connection pipes, footing drains,
weepholes and horizontal drains (if required), drainage gutter, reinforcing steel and shotcrete
for the permanent shotcrete facing and nail head bearing plates and nuts for the soil nail walls
shown on the Plans. The Work shall include any preparatory trimming and cleaning of soil/rock
surfaces and shotcrete cold joints to receive new shotcrete.
Shotcrete shall comply with the requirements of ACI 506.2, "Specifications for Materials, Pro-
portioning and Application of Shotcrete” except as otherwise specified. Shotcrete shall consist
of an application of one or more layers of concrete conveyed through a hose and pneumatically
projected at a high velocity against a prepared surface.
Shotcrete may be produced by either a wet-mix or dry-mix process. The wet-mix process con-
sists of thoroughly mixing all the ingredients except accelerating admixtures, but including the
mixing water, introducing the mixture into the delivery equipment and delivering it by positive
displacement, to the nozzle. The wet-mix shotcrete shall then be airjetted from the nozzle at
high velocity onto the surface. The dry-mix process consists of shotcrete without mixing water
that is conveyed through the hose pneumatically with the mixing water introduced at the nozzle.
For additional descriptive information, the Contractor's attention is directed to the American
Concrete Institute ACI 506R "Guide to Shotcrete."
The Standard Specifications and/or CIP Facing Special Provisions cover CIP concrete facing
construction (if required). The Permanent Soil Nails and Wall Excavation Specifications cover
soil nails and wall excavation. Soil nail wall instrumentation (if required) is covered by the Soil
Nail Wall Instrumentation Specification.
Where the imperative mood is used within this Specification for conciseness, "the Contractor
shall" is implied.

C.1.1 Contractor's Experience Requirements
Workers, including foremen, nozzlemen, finishers and delivery equipment operators, shall be
fully experienced to perform the work. All shotcrete nozzlemen on this project shall have experi-
ence on at least 3 projects in the past 3 years in similar permanent shotcrete application work
totaling at least 1000 square meters (11,000 square feet) of wall face area and shall demon-
Appendix to the Recommended Guidelines for Permanent Soil Nails                    Page 33 of 4746
strate ability to satisfactorily place the shotcrete. Finishers shall have experience on at least 3
projects in the past 3 years in similar permanent shotcrete application work totaling at least
1000 square meters (11,000 square feet) of wall face area.
Initial qualification of nozzlemen will be based either on previous ACI certification or satisfactory
completion of preconstruction test panels. The requirement for nozzlemen to shoot preconstruc-
tion qualification test panels will be waived for nozzlemen who can submit documented proof
they have been certified in accordance with the ACI 506.3R Guide to Certification of Shotcrete
Nozzlemen. The Certification shall have been done by a recognized shotcrete testing lab and/or
recognized shotcreting consultant and have covered the type of shotcrete to be used ( plain
wet-mix, plain dry-mix or steel fiber reinforced. (See Commentary 1.1). All nozzlemen will be re-
quired to periodically shoot production test panels during the course of the Work at the fre-
quency specified herein.
Notify the Engineer not less than 2 days prior to the shooting of preconstruction test panels to
be used to qualify nozzlemen without previous ACI certification. Use the same shotcrete mix
and equipment to make qualification test panels as those to be used for the soil nail wall shot-
crete facing. Initial qualification of the nozzlemen will be based on a visual inspection of the
shotcrete density and void structure and on achieving the specified 3-day and 28-day compres-
sive strength requirements determined from test specimens extracted from the preconstruction
test panels. Preconstruction and production test panels, core extraction and compressive
strength testing shall be conducted in accordance with ACI 506.2 and AASHTO T24/ASTM
C42, unless otherwise specified herein. Nozzlemen without ACI Certification will be allowed to
begin production shooting based on satisfactory completion of the preconstruction test panels
and passing 3-day strength test requirements. Continued qualification will be subject to passing
the 28-day strength tests and shooting satisfactory during production test panels.

C.1.2 Construction Submittals
At least 15 calendar days before the planned start of shotcrete placement submit 5 copies of
the following information, in writing, to the Engineer for review:


1. Written documentation listing at least 5 permanent structural shotcrete walls successfully
   completed within the past 3 years, including photographs of the project as well as names,
   addresses, and phone numbers of the owner's representative.
2. Written documentation of the finisher's and nozzlemen’s qualifications including proof of ACI
   certification (if applicable).
3. Proposed methods of shotcrete placement and of controlling and maintaining facing align-
   ment and location and shotcrete thickness.
4. Shotcrete mix design including:
   Type of Portland cement.
   Aggregate source and gradation.
   Proportions of mix by weight and water-cement ratio.
   Proposed admixtures, manufacturer, dosage, technical literature.
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   Previous strength test results for the proposed shotcrete mix completed within one year of
   the start of shotcreting may be submitted for initial verification of the required compressive
   strengths at start of production work.
5. Certificates of Compliance, manufacturers’ engineering data and installation instructions for
   the geotextile, geocomposite drain strip, drain grate and accessories.
6. Certificates of Compliance for bearing plates, nuts, drainage aggregate and PVC drain pip-
   ing.


The Engineer will approve or reject the Contractor’s Submittals within 10 calendar days after
receipt of a complete submission. The Contractor will not be allowed to begin wall construction
or incorporate materials into the work until submittal requirements are satisfied and found ac-
ceptable to the Engineer. Changes or deviations from the approved submittals must be re-
submitted for approval. No adjustments in contract time will be allowed due to incomplete sub-
mittals.

C.1.3 Pre-Construction Meeting
A pre-construction meeting scheduled by the Engineer will be held prior to the start of wall con-
struction. Attendance is mandatory. The shotcrete Contractor, if different than the soil nail spe-
cialty Contractor, shall attend. See Section 1.4 of the Permanent Soil Nail and Wall Excavation
Specification.

C.2.0 Materials
All materials for shotcrete shall conform to the following requirements


Cement                               AASHTO M85 / ASTM C150, Type I, II, III or V.
Fine Aggregate                       AASHTO M6 / ASTM C33 clean, neutral
Coarse Aggregate                     AASHTO M80, Class B for quality
Water                                Clean and Potable, AASHTO M157 / ASTM C94
Chemical Admixtures
         Accelerator                 Fluid type, applied at nozzle, meeting requirements of
                                     AASHTO M194 / ASTM C494 / ASTM C1141
         Air-Entraining Agent        AASHTO M154 / ASTM C260
         Water-reducer and Su- AASHTO M194 / ASTM C494 Type A, C, D, E, F, or
         perplastisizer        G.
         Retarders                   ASHTO M194 / ASTM C494 Type B or D.
Mineral Admixtures
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         Fly Ash                  AASHTO M295/ASTM C618 Type F or C, cement
                                  replacement up to 35 percent by weight of cement.
         Silica Fume              ASTM C1240, 90 Percent minimum silicon dioxide
                                  solids content, not to exceed 12 percent by weight of
                                  cement
Welded Wire Fabric                AASHTO M55/ASTM A185 or A497
Reinforcing Bars for Shotcrete AASHTO M31/ASTM A615, Grade 420, deformed
Facing
Bearing Plates                    AASHTO M183/ASTM A36,
Nuts                              AASHTO M291, grade B, hexagonal, fitted with bev-
                                  eled washer or spherical seat to provide uniform
                                  bearing
Curing Compounds                  AASHTO M148, Type ID or Type 2
Prepackaged Shotcrete             ASTM C928
Drainage Geotextile
         For Wall Footing Drain   AASHTO M288 Class 2, Permittivity min. 0.2 per
                                  second; AOS 0.25 mm max.
         For Drain Strip          AASHTO M288 Class 3, Permittivity min. 0.2 per
                                  second; AOS 0.25 mm max
Drainage Aggregate                AASHTO M43/ASTM C33 No. 67 with no more than
                                  two percent passing the 0.075 mm sieve
Geocomposite Drain Strip          Miradrain 6000, Amerdrain 500 or approved equal
Film Protection                   Polyethylene films per AASHTO M-171
PVC Connector and Drain pipes:
         Pipe                     ASTM 1785 Schedule 40 PVC, solid and perforated
                                  wall, cell classification 12454-B or 12354-C, wall
                                  thickness SDR 35, with solvent weld or elastomeric
                                  gasket joints
         Fittings                 ASTM D3034, cell classification 12454-B or 12454-C,
                                  wall thickness SDR35, with solvent weld or elas-
                                  tomeric gasket joints
         Solvent Cement           ASTM D2564
         Primer                   ASTM F656
Appendix to the Recommended Guidelines for Permanent Soil Nails                 Page 36 of 4746
Materials shall be delivered, stored and handled to prevent contamination, segregation, corro-
sion or damage. Store liquid admixtures to prevent evaporation and freezing.
Drainage geotextile and geocomposite drain strips shall be provided in rolls wrapped with a pro-
tective covering and stored in a manner which protects the fabric from mud, dirt, dust, debris,
and shotcrete rebound. Protective wrapping shall not be removed until immediately before the
geotextile or drain strip is installed. Extended exposure to ultra-violet light shall be avoided.
Each roll of geotextile or drain strip in the shipment shall be labeled to identify the production
run.

C.2.1 Shotcrete Mix Design.
The Contractor must receive notification from the Engineer that the proposed mix design and
method of placement are acceptable before shotcrete placement can begin.

C.2.1.1 AGGREGATE.
Aggregate for shotcrete shall meet the strength and durability requirements of AASHTO
M6/M80 and the following gradation requirements: (See Commentary 2.1.1)
      Sieve-Size Percent Passing by Weight
      12.5    mm              100
       9.50   mm             90-100
       4.75   mm             70-85
       2.36   mm             50-70
       1.18   mm             35-55
       0.60   mm             20-35
       0.30   mm              8-20
       0.15   mm              2-10



C.2.1.2 PROPORTIONING AND USE OF ADMIXTURES.
Proportion the shotcrete to be pumpable with the concrete pump furnished for the work, with a
cementing materials content of at least 390 kilograms per cubic meter (660 lbs per cubic yard)
and water/cement ratio not greater than 0.45. (See Commentary 2.1.2). Do not use admixtures
unless approved by the Engineer. Thoroughly mix admixtures into the shotcrete at the rate
specified by the manufacturer. Accelerators (if used) shall be compatible with the cement used,
be non-corrosive to steel and not promote other detrimental effects such as cracking or exces-
sive shrinkage. The maximum allowable chloride ion content of all ingredients shall not exceed
0.10% when tested to AASHTO 1260.

C.2.1.3 AIR ENTRAINMENT
Air entrainment is required for wet-mix shotcrete. The air content measured at the truck shall be
between 7 and 10 percent when tested in accordance with AASHTO T152/ASTM C231. Air en-
trainment is not required in dry-mix shotcrete. (See Commentary 2.1.3)
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C.2.1.4 STRENGTH AND DURABILITY REQUIREMENTS.
Provide a shotcrete mix capable of attaining 14 MPa (2000 psi) compressive strength in 3 days
and 28 MPa in 28 days. (See Commentary 2.1.4a). The average compressive strength of each
set of three test cores extracted from test panels or wall face must equal or exceed 85 percent
of the specified compressive strength, with no individual core less than 75 percent of the speci-
fied compressive strength, in accordance with ACI 506.2. The boiled absorption of shotcrete,
when tested in accordance with ASTM C642 at 7 days, shall not exceed 8.0 percent. (See
Commentary 2.1.4b)

C.2.1.5 MIXING AND BATCHING.
Aggregate and cement may be batched by weight or by volume in accordance with the re-
quirements of ASTM C94 or AASHTO M241/ASTM C685. Mixing equipment shall thoroughly
blend the materials in sufficient quantity to maintain placing continuity. Ready mix shotcrete
shall comply with AASHTO M157. Shotcrete shall be batched, delivered, and placed within 90
minutes of mixing. The use of retarding admixtures may extend application time beyond 90
minutes if approved by the Engineer.
Premixed and packaged shotcrete mix may be provided for on-site mixing. The packages shall
contain materials conforming to the Materials section of this specification. Placing time limit af-
ter mixing shall be per the manufacturers' recommendations.

C.2.2 Field Quality Control.
Both preconstruction test panels (for nozzlemen without previous ACI certification) and produc-
tion test panels or test cores from the wall facing are required. Shotcreting and coring of test
panels shall be performed by qualified personnel in the presence of the Engineer. The Contrac-
tor shall provide equipment, materials, and personnel as necessary to obtain shotcrete cores for
testing including construction of test panel boxes, field curing requirements and coring. Com-
pressive strength testing will be performed by the Engineer. (See Commentary 2.2). Shotcrete
final acceptance will be based on the 28-day strength.
Shotcrete production work may commence upon initial approval of the design mix and nozzle-
men and continue if the specified strengths are obtained. The shotcrete work by a crew will be
suspended if the test results for their work does not satisfy the strength requirements. The Con-
tractor shall change all or some of the following: the mix, the crew, the equipment or the proce-
dures. Before resuming work, the crew must shoot additional test panels and demonstrate that
the shotcrete in the panels satisfies the specified strength requirements. The cost of all work
required to obtain satisfactory strength tests will be borne by the Contractor.

C.2.2.1 PRECONSTRUCTION TEST PANELS.
Each nozzleman without previous ACI certification shall furnish at least two preconstruction test
panels for each proposed mixture being considered and for each shooting position to be en-
countered on the job. Preconstruction test panels shall be made prior to the commencement of
production work using the same equipment, materials, mixture proportions and procedures pro-
posed for the job
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Make preconstruction test panels with minimum dimensions of 750 x 750 mm square and at
least 100 mm thick. Slope the sides of preconstruction and production test panels at 45 de-
grees over the full panel thickness to release rebound. (See Commentary 2.2.1). One precon-
struction test panel shall include the maximum anticipated reinforcing congestion shown on the
Plans. Cores extracted from the test panel shall demonstrate encapsulation of the reinforce-
ment in accordance with ACI 506.2 equal to core grade 2 or better. The other preconstruction
test panel shall be constructed without reinforcement and have cores extracted for absorption
and compressive strength testing.

C.2.2.2 PRODUCTION TEST PANELS.
 Furnish at least one production test panel or, in lieu of production test panels, nine 75 mm di-
ameter cores taken from the shotcrete facing, during the first production application of shotcrete
and henceforth for every 500 m2 of shotcrete placed. (See Commentary 2.2.2). Construct the
production test panels simultaneously with the shotcrete facing installation at times designated
by the Engineer. Make production test panels with minimum full thickness dimensions of
450x450 mm square and at least 100 mm thick.

C.2.2.3 TEST PANEL CURING, TEST SPECIMEN EXTRACTION AND TESTING.
Immediately after shooting, field moist cure the test panels by covering and tightly wrapping with
a sheet of material meeting the requirements of ASTM Cl71 until they are delivered to the test-
ing lab or test specimens are extracted. Do not immerse the test panels in water. Do not further
disturb test panels for the first 24 hours after shooting. Provide at least three 75 mm diameter
core samples cut from each preconstruction test panel with reinforcement for core grading.
(See Commentary 2.2.3a). Provide at least nine 75 mm diameter core samples cut from each
unreinforced preconstruction and production test panel for absorption and compressive strength
testing. Contractor has the option of extracting test specimens from test panels in the field or
transporting to another location for extraction. Keep panels in their forms when transported. Do
not take cores from the outer 150 mm of test panels measured in from the top outside edges of
the panel form. (See Commentary 2.2.3b). Trim the ends of the compressive strength cores to
provide test cylinders at least 75 mm long. Do not trim the ends of the cores to be tested for
boiled absorption. If the Contractor chooses to take cores from the wall face in lieu of making
production test panels, locations will be designated by the Engineer. Clearly mark the cores and
container to identify the core locations and whether they are for preconstruction or production
testing. If for production testing, mark the section of the wall represented by the cores on the
cores and container. Immediately wrap cores in wet burlap or material meeting the require-
ments of ASTM Cl71 and seal in a plastic bag. Deliver cores to the Engineer or testing lab, as
directed by the Engineer, within 48 hours of shooting the panels. The remainder of the panels
will become the property of the Contractor. Compressive strength and boiled absorption testing
will be performed by the Engineer. Upon delivery to the testing lab, samples will be placed in
the moist room until the time of test. When the test length of a core is less than twice the
diameter, the correction factors given in AASHTO T24/ASTM C42 will be applied to obtain the
compressive strength of individual cores. Three cores will be tested at 3 days and three cores
will be tested at 28 days for compressive strength per AASHTO 724/ASTM C42. Three cores
will be tested at 7 days for boiled absorption per ASTM C642.
Appendix to the Recommended Guidelines for Permanent Soil Nails                  Page 39 of 4746
Fill core holes in the wall by dry-packing with non-shrink patching mortar after the holes are
cleaned and dampened. Do not fill core holes with shotcrete.

C.3.0 CONSTRUCTION REQUIREMENTS

C.3.1 Wall Drainage Network.
Install and secure all elements of the wall drainage network as shown on the Plans, as specified
herein, or as required by the Engineer to suit the site conditions. The drainage network shall
consist of installing geocomposite drain strips, PVC connection pipes and wall footing drains as
shown on the Plans or as directed by the Engineer. Exclusive of the wall footing drains, all ele-
ments of the drainage network shall be installed prior to shotcreting.
Unanticipated subsurface drainage features exposed in the excavation cut face shall be cap-
tured independently of the wall drainage network and shall be mitigated prior to shotcrete appli-
cation in accordance with Section 3.1 of the Soil Nail and Wall Excavation Specification. Costs
due to the required mitigation will be paid for as Extra Work.

C.3.1.1 GEOCOMPOSITE DRAIN STRIPS.
Install geocomposite drain strips centered between the columns of nails as shown on the Plans.
The drain strips shall be at least 300 mm wide and placed with the geotextile side against the
ground. Secure the strips to the excavation face and prevent shotcrete from contaminating the
ground side of the geotextile. Drain strips will be continuous. Splices shall be made with a 300
mm minimum overlap such that the flow of water is not impeded. Repair damage to the geo-
composite drain strip, which may interrupt the flow of water. (See Commentary 3.1.1)

C.3.1.2 FOOTING DRAINS.
Install footing drains at the bottom of each wall as shown on the Plans. The drainage geotextile
shall envelope the footing drain aggregate and pipe and conform to the dimensions of the
trench. Overlap the drainage geotextile on top of the drainage aggregate as shown on the
Plans. Replace or repair damaged or defective drainage geotextile.

C.3.1.3 CONNECTION PIPES AND WEEPHOLES.
Install connection pipes as shown on the Plans. Connection pipes are lengths of solid PVC pipe
installed to direct water from the geocomposite drain strips into a footing drain or to the exposed
face of the wall. Connect the connection pipes to the drain strips using either prefabricated
drain grates as shown on the Plans or using the alternate connection method described below.
Install the drain grate per the manufacturers recommendations. The joint between the drain
grate and the drain strip and the discharge end of the connector pipe shall be sealed to prevent
shotcrete intrusion. Connection pipes that end at the footing drain shall be extended to the edge
of the drain. Do not puncture the drainage fabric around the footing drain.
The alternative acceptable method for connection of the connector pipe to the drain strip in-
volves cutting a hole slightly larger than the diameter of the pipe into the strip plastic core but
not through the geotextile. Wrap both ends of the connection pipe in geotextile in a manner that
Appendix to the Recommended Guidelines for Permanent Soil Nails                  Page 40 of 4746
prevents migration of fines through the pipe. Tape or seal the inlet end of the pipe where it
penetrates the drain strip and the discharge end of the connector pipe in a manner that pre-
vents penetration of shotcrete into the drain strip or pipe. To assure passage of groundwater
from the drain strip into the connector pipe, slot the inlet end of the connector pipe at every 45
degrees around the perimeter of the pipe to a depth of 6 mm.
Weepholes, if required, shall be provided through the shotcrete, facing to drain water from be-
hind the facing. Install as shown on the Plans. Use PVC pipe to form the weephole through the
shotcrete. Cover the end of the pipe contacting the soil with a drainage geotextile. Prevent
shotcrete intrusion into the discharge end of the pipe. (See Commentary 3.1.3)

C.3.2 Permanent Shotcrete Facing

C.3.2.1 SHOTCRETE ALIGNMENT AND THICKNESS CONTROL.
Ensure that the thickness of shotcrete satisfies the minimum requirements shown on the Plans
using shooting wires, thickness control pins, or other devices acceptable to the Engineer. Install
thickness control devices normal to the surface such that they protrude the required shotcrete
thickness outside the surface and maintain a plane surface. The maximum distance between
the wires on any surface shall be equal to the vertical nail spacing. Ensure that the alignment
wires are tight, true to line, and placed to allow further tightening. Remove shooting wires after
completion of shotcreting and/or screeding. Ensure that the front face of the shotcrete does not
extend beyond the limits shown on the Plans.

C.3.2.2 SURFACE PREPARATION.
Clean the face of the excavation and other surfaces to be shotcreted of loose materials, mud,
rebound, overspray or other foreign matter that could prevent or reduce shotcrete bond. Protect
adjacent surfaces from overspray during shooting. Avoid loosening, cracking, or shattering the
ground during excavation and cleaning. Remove any surface material which is so loosened or
damaged, to a sufficient depth to provide a base that is suitable to receive the shotcrete. Re-
move material that loosens as the shotcrete is applied . Cost of additional shotcrete is incidental
to the work. Divert water flow and remove standing water so that shotcrete placement will not
be detrimentally affected by standing water. Do not place shotcrete on frozen surfaces.

C.3.2.3 DELIVERY AND APPLICATION.
Maintain at all times a clean, dry, oil-free supply of compressed air sufficient for maintaining
adequate nozzle velocity and for simultaneous operation of a blow pipe for cleaning away re-
bound. The equipment shall be capable of delivering the premixed material accurately, uni-
formly, and continuously through the delivery hose. Control shotcrete application thickness,
nozzle technique, air pressure, and rate of shotcrete placement to prevent sagging or sloughing
of freshly-applied shotcrete.
Apply the shotcrete from the lower part of the area upwards to prevent accumulation of re-
bound. Orient nozzle at a distance and approximately perpendicular to the working face so that
rebound will be minimal and compaction will be maximized. Pay special attention to encapsulat-
Appendix to the Recommended Guidelines for Permanent Soil Nails                     Page 41 of 4746
ing reinforcement. Care shall be taken while encasing reinforcing steel and mesh to keep the
front face of the reinforcement clean during shooting operations, so that shotcrete builds up
from behind, to encase the reinforcement and prevent voids and sand pockets from forming.
Use a blow pipe to remove rebound and overspray immediately ahead of the nozzle. Do not
work rebound back into the construction. Remove rebound that does not fall clear of the work-
ing area. Hardened rebound and hardened overspray shall be removed prior to application of
additional shotcrete, using abrasive blast cleaning, chipping hammers, high pressure water
blasting or other suitable techniques. When the thickness of a individual shotcrete layer is 150
mm or greater, or when shotcreting is conducted through two curtains of reinforcement, place
shotcrete by the bench gunning method. The bench gunning method shall consist of building up
a thick layer of shotcrete from the bottom of the lift and maintaining the top surface at approxi-
mately a 45-degree slope. Where shotcrete is used to complete the top ungrouted zone of the
nail drill hole near the face, position the nozzle into the mouth of the drill hole to completely fill
the void.
A clearly defined pattern of continuous horizontal or vertical ridges or depressions at the rein-
forcing elements after they are covered with shotcrete will be considered an indication of insuf-
ficient reinforcement cover or poor nozzle techniques. In this case the application of shotcrete
shall be immediately suspended and the Contractor shall implement corrective measures be-
fore resuming the shotcrete operations. The shotcreting procedure may be corrected by adjust-
ing the nozzle distance and orientation, by insuring adequate cover over the reinforcement, by
adjusting the water content of the shotcrete mix or other means. Adjustment in water content of
wet-mix will require requalifying the shotcrete mix.
When using multiple layer shotcrete construction, the surface of the receiving layer shall be
prepared before application of a subsequent layer, by either: (a) Brooming the stiffening layer
with a stiff bristle broom to remove all loose material, rebound, overspray or glaze, prior to the
shotcrete attaining initial set: or (b) If the shotcrete has set, surface preparation shall be de-
layed at least 24 hours, at which time the surface shall be prepared by sandblasting or high
pressure water blasting to remove all loose material, rebound, hardened overspray, glaze, or
other material that may prevent adequate bond.

C.3.2.4 DEFECTIVE SHOTCRETE.
The Engineer shall have authority to accept or reject the shotcrete work. Shotcrete which does
not conform to the project specifications may be rejected either during the shotcrete application
process, or on the basis of tests on the test panels or completed work. Repair shotcrete surface
defects as soon as possible after placement. Remove and replace shotcrete, which exhibits
segregation, honeycombing, lamination, voids, or sand pockets. In-place shotcrete determined
not to meet the specified strength requirement will be subject to remediation as determined by
the Engineer. Possible remediation options include placement of additional shotcrete thickness
or removal and replacement, at the Contractor's cost.

C.3.2.5 CONSTRUCTION JOINTS.
Taper construction joints uniformly toward the excavation face over a minimum distance equal
to the thickness of the shotcrete layer. Square joints are not permitted. The surface of the joints
Appendix to the Recommended Guidelines for Permanent Soil Nails                 Page 42 of 4746
shall be rough, clean, and sound. Provide a minimum reinforcement overlap at reinforcement
splice joints as shown on the Plans. Clean and wet the surface of a joint before adjacent shot-
crete is applied. (See Commentary 3.25). Where shotcrete is used to complete the top un-
grouted zone of the nail drill hole near the face, to the maximum extent practical, clean and
dampen the upper grout surface to receive shotcrete, similar to a construction joint.

C.3.2.6 FINAL FACE FINISH.
Shotcrete finish shall be either an undisturbed gun finish as applied from the nozzle or a rod,
broom, wood flog rubber float, steel trowel or rough screeded finish as shown on the Plans or
specified herein. (See Commentary 3.2 6).

C.3.2.7 ATTACHMENT OF NAIL HEAD BEARING PLATE AND NUT.
Attach a bearing plate and nut to each nail head as shown on the Plans. While the shotcrete is
still plastic and before its initial set, uniformly seat the plate on the shotcrete by hand wrench
tightening the nut. Where uniform contact between the plate and the shotcrete cannot be pro-
vided, set the plate in a bed of grout. After grout has set for 24 hours, hand wrench tighten the
nut. Embed the bearing plate and nut in the wall as shown on the Plans. Ensure full shotcrete
encapsulation of the bearing plate and nut free of any voids or pockets behind the plate. Ensure
bearing plates with headed studs are located within the tolerances shown on the Plans or speci-
fied herein.

C.3.2.8 WEATHER LIMITATIONS.
Protect the shotcrete if it must be placed when the ambient temperature is below 5 oC and fal-
ling or when it is likely to be subjected to freezing temperatures before gaining sufficient
strength. Maintain cold weather protection until the in-place compressive strength of the shot-
crete is greater than 5 MPa. Cold weather protection includes blankets, heating under tents, or
other means acceptable to the Engineer. The temperature of the shotcrete mix, when depos-
ited, shall be not less than 10 oC or more than 35 oC. Maintain the air in contact with shotcrete
surfaces at temperatures above 0 oC for a minimum of 7 days.
If the prevailing ambient conditions (relative humidity, wind speed, air temperature and direct
exposure to sunlight) are such that the shotcrete develops plastic shrinkage and/or early drying
shrinkage cracking, shotcrete application shall be suspended. The Contractor shall: (a) Re-
schedule the work to a time when more favorable ambient conditions prevail; and/or (b) Adopt
corrective measures, such as installation of sun-screens, wind breaks or fogging devices, to
protect the work. Remove and replace newly placed shotcrete exposed to rain that washes out
cement or otherwise makes the shotcrete unacceptable.

C.3.2.9 CURING.
Protect permanent shotcrete from loss of moisture for at least 7 days after placement. Cure
shotcrete, by methods that will keep the shotcrete surfaces adequately wet and protected dur-
ing the specified curing period. Commence curing within 1 hour of shotcrete application. When
the ambient temperature exceeds 27 oC, plan the Work such that curing can commence imme-
Appendix to the Recommended Guidelines for Permanent Soil Nails                  Page 43 of 4746
diately after finishing. Complete curing in accordance with the following requirements. (See
Commentary 3.29)

C.3.2.9.1 W ATER CURING.
Regulate the rate of water application to keep the surface continuously wet and to provide com-
plete surface coverage with a minimum of runoff. The use of intermittent wetting procedures
which allow the shotcrete to undergo wetting and drying during the curing period is prohibited.

C.3.2.9.2 MEMBRANE CURING.
Do not use curing compounds on any surfaces against which additional shotcrete or other ce-
mentitious finishing materials are to be bonded unless the surface is thoroughly sandblasted in
a manner acceptable to the Engineer. Membrane curing compounds are to be spray applied as
quickly as practical after initial shotcrete set at a coverage of not less than 2.5 liter/ m2.

C.3.2.9.3 FILM CURING.
Film curing with polyethylene sheeting may be used to supplement water curing on shotcrete
that will be covered later with additional shotcrete or concrete. Spray the shotcrete surface with
water immediately prior to installation of the polyethylene sheeting. Polyethylene sheeting shall
completely cover the surfaces. Overlap the sheeting edges for proper sealing and anchorage.
Joints between sheets shall be sealed. Promptly repair any tears, holes, and other damage.
Anchor sheeting as necessary to prevent billowing.

C.3.2.10 PERMANENT SHOTCRETE FACING TOLERANCES.
Construction tolerances for the permanent shotcrete facing are as follows:
Horizontal Location of Wire Mesh; Rebar; Headed Studs on Bearing Plates,
from Plan location:                                       + or - 10 mm
Headed studs location on bearing plate, from plan location:   6 mm
Spacing between reinforcing bars, from plan dimension:        25 mm
Reinforcing lap, from specified dimension:                    - 25mm
Complete thickness of shotcrete, from plan dimension;
If troweled or screeded:                                      - 15 mm
If left as shot:                                              - 30 mm
Planeness of finish face surface-gap under 3 meter straightedge-any direction:
If troweled or screeded:                                       15 mm
If left as shot:                                               30 mm
Nail head bearing plate, deviation from parallel to wall face: 10 degrees

C.3.3 Backfilling Behind Wall Facing Upper Cantilever.
Compact backfill within 1 meter behind the wall facing upper cantilever using light mechanical
tampers.
Appendix to the Recommended Guidelines for Permanent Soil Nails                   Page 44 of 4746
C.3.4 Safety Requirements.
Nozzlemen and helpers shall be equipped with gloves, eye protection, and adequate protective
clothing during the application of shotcrete. The Contractor is responsible for meeting all fed-
eral, state and local safety code requirements.

C.4.0 METHOD OF MEASUREMENT.
The shotcrete facing will be measured in square meters of the shotcrete area completed and
accepted in the final work. The net area lying in a plane of the outside front face of the structure
as shown on the Plans will be measured. No measurement or payment will be made for addi-
tional shotcrete or CIP concrete needed to fill voids created by irregularities in the cut face, ex-
cavation overbreak or inadvertent excavation beyond the plan final wall face excavation line, or
failure to construct the facing to the specified line and grade tolerances. The final pay quantity
shall include all structural shotcrete, admixtures, reinforcement, welded wire mesh, wire holding
devices, wall drainage materials, bearing plates and nuts, test panels and all sampling, testing
and reporting required by the Plans and this Specification. The final pay quantity shall be the
design quantity increased or decreased by any changes authorized by the Engineer.

5.0 Basis of Payment
The accepted quantity measured as provided above will be paid for at the contract unit price per
square meter. Payment will be full compensation for furnishing all equipment, materials, labor,
tools and incidentals necessary to complete the work as specified and as detailed on the Plans,
including the work required to provide the proper shotcrete facing alignment and thickness con-
trol. All wall drainage materials including geocomposite drain strips, connection pipes, drain
grates, drain aggregate and geotextile, fittings, and accessories are considered incidental to the
shotcrete facing and will not be paid separately.
Payment will be made for the following bid item included in the bid form:
                Pay Item                               Measurement Unit
      Permanent Shotcrete Facing                  Square Meter (Sqaure Feet)
Appendix to the Recommended Guidelines for Permanent Soil Nails                     Page 45 of 4746

                          COMMENTARY TO
            PERMANENT SHOTCRETE FACING AND WALL DRAINAGE
                        GUIDE SPECIFICATION


C.1.1 EXPERIENCE REQUIREMENTS
C.1.1 Specifier: If shotcrete nozzlemen have not been previously certified, it may be practical
for the Contractor to arrange to certify them during the preconstruction test program through lo-
cal testing laboratories or other experienced ACI recognized shotcrete specialists.

C.2.1. SHOTCRETE MIX DESIGN
C.2.1.1        Specifier. The aggregate gradation presented is commonly used for dry-mix and
wet-mix shotcrete and has been satisfactorily used for a number of soil nailing projects. It re-
quires a minimum of 15% of coarse aggregate sizes, (i.e. greater than 4.75 mm). Higher coarse
aggregate contents would be preferable from a quality standpoint but may present problems
with regard to pumping and shooting. In some areas, a mix consisting of only fine aggregate
may be proposed because the local shotcrete industry is accustomed to that material. This is
particularly true for areas where dry-mix is prominent. Such mixes will have a higher propensity
for shrinkage but will have reduced rebound. They are suitable for construction facings but not
permanent facings.
C.2.1.2    Specifier. A higher maximum water cement ratio of 0.50 maybe permissible in
non- demanding exposures.
C.2.1.3        Specifier. Air content should only be required in the specification where wet-mix
shotcrete is used and shotcrete is permanent (i.e., services the long term permanent loads). It
is not practical to require air entrainment in dry-mix shotcrete. However, such shotcrete has
been demonstrated to generally contain some air voids and often enough for providing protec-
tion for freezing and thawing. The high 7 to 10 percent air content specified for wet-mix shot-
crete reflects the fact that a significant percentage of the air is lost during application due to the
impact velocities.
C.2.1.4a       Specifier. A 3 day strength criterion has been selected in addition to the traditional
28 days because soil nailing shotcrete is normally required to accept loads at an early age and
therefore it is the early strength that is critical. The 28 day strength is included because of the
need to compare it with the specified ultimate strength of the facing as used in the structural
design.
C.2.1.4b       Specifier. The boiled absorption test is a measure of the shotcrete void content
and therefore compaction. Boiled absorption tests are not required for temporary construction
facings, only permanent. The value of 8% boiled absorption is known to be achievable with rea-
sonable quality shotcrete containing coarse aggregate corresponding to the gradation specified
here. It is commonly used in many other specifications. However, the majority of the experience
with the use of this value comes from good quality aggregates with correspondingly lower ab-
Appendix to the Recommended Guidelines for Permanent Soil Nails                   Page 46 of 4746
sorptions. Some areas of the United States have aggregates with high absorptions, e.g. sedi-
mentaries, and higher shotcrete absorption values will automatically result since some of the
aggregrate is exposed in the cutface of the test core. In these cases, a higher absorption value,
say 9%, should be specified.

C.2.2 FIELD QUALITY CONTROL
C.2.2 Specifier. If testing is to be the Contractor's responsibility, modify the specification ac-
cordingly.
C.2.2.1     Specifier. Test panels with 45 degree sloped sides are recommended to minimize
entrapment of rebound when shooting the test panel and for ease of stripping the form.
C.2.2.2     Specifier. The 500 square meter testing area requirement may need to be ad-
justed depending on the area of wall to be constructed on the contract.
C.2.2.3a     Specifier. 75 mm diameter cores are adequate for reinforcement size No. 13M or
smaller. Specify 100 mm diameter cores if reinforcement size is larger than No. 13M.
C.2.2.3b      Specifier. Most Authorities require that the outside 150 mm measured in from the
top outside edges of the panel form be discarded because it typically contains rebound or over-
spray and is not representative.

C.3.1 WALL DRAINAGE NETWORK
C.3.1.1     Specifier. At the designers option, horizontal geocomposite drain strips may be
included behind horizontal shotcrete construction joints and/or where zones of localized
groundwater seepage is encountered during construction.
C.3.1.3       Specifier. Longer horizontal drains are typically not included in the project specifi-
cation unless more significant groundwater is anticipated at the excavation cut face. The project
geotechnical engineer should assess the need for horizontal drains and determine the length
and spacing. Most highway agencies have standard specifications and plan details covering
horizontal drain material and installation requirements. Where deemed necessary, horizontal
drains can be included on the Plans and the following verbiage added to the Specifications:
   Slotted PVC horizontal drains, if required, shall be installed as shown on the Plans. Install
   horizontal drains in drill holes that slope upward at an inclination of 2 to 5 degrees. Provide
   PVC horizontal drain pipe meeting the materials requirements set forth in the Standard
   Specifications. Attach a solid inlet pipe to the slotted pipe approximately 300 mm. behind the
   back of the shotcrete facing. Seal the annular space between the inlet pipe and the drill hole
   with bentonite pellets or non shrink grout. Connect the inlet pipe to the discharge pipe that
   will empty directly into the footing drain, as shown on the Plans.

C.3.2 PERMANENT SHOTCRETE FACING
C.3.2.5       Specifier. Where the finished walls are constructed "top-down" in one full thick-
ness layer, i.e. the shotcrete serves as the final facing, the contractor should demonstrate that
his techniques will preclude sag or joint separation between excavation lifts. This typically oc-
Appendix to the Recommended Guidelines for Permanent Soil Nails                     Page 47 of 4746
curs in walls thicker than 100 mm due to consolidation of the loose backfill material placed to
provide a reinforcing splice below the lift. It has been demonstrated that joint separation can be
mitigated by building the shotcrete in each lift from the bottom while allowing adequate time for
consolidation of loose splice backfill.
C.3.2.6      Specifier. Specify the type finish to be applied If the final shotcrete finish face is to
be painted such as with a pigmented sealer, add here or reference the applicable specification.
C.3.2.9       Specifier. Curing requirements for shotcrete are only necessary where the shot-
crete is designed to be permanent and has to service the long-term wall loadings. Shotcrete for
temporary construction walls does not require curing.

				
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