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Review of Compaction Principles

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					    Objectives
 Be able to use basic    Be able to perform
  volume weight            basic compaction test
  equations                (LAB EXERCISE)
 Understand principal
                          plot compaction data
  of soil compaction.      and evaluate for
 Explain how the          accuracy
  compaction test is      Understand procedure
  used in design and       for Atterberg Limit
  quality control          Tests (LAB
                           EXERCISE)
Review of Compaction Principles

 Compaction  Tests are not suitable for
 soils with more than 30 % by weight of
 the sample being larger than a ¾”
 sieve.
 Compactiontests are not usually
 performed on soils with 12 % or fewer
 fines
Review of Compaction Principles

 Relative  Density testing is used for
  clean sands and gravels – covered later
  in class
 Standard Procedures for testing are
  available for soils with some gravel
  (less than the maximum allowable
  content)
Principle of compaction
 Theory developed by R.R. Proctor in
 1930’s in California
 Three Factors determine the density
 that results from soil compaction
Proctor Developed Principle

Three variables determine the
 density of a compacted soil
  – The energy used in compaction
  – The water content of the soil
  – The properties of the soil
State Diagram
Dry Density, pcf




                        100 %
                      saturation
                        curve




                   Water content, %
State Diagram
Dry Density, pcf




                   Water content, %
Energy Used in Compaction

 Assume   you have some clay soil that is
  at a water content of 16 percent.
 Look at the effect different compaction
  energy has on the density of the soil.
 Energy expressed as number of passes
  of a sheepsfoot roller on a lift of soil
                   At this water content, energy has
                   a large effect on compacted
                   density
Dry Density, pcf



                         10 passes of
                          equipment
                            4 passes of
                            equipment
                            3 passes of
                            equipment
                            2 passes of
                            equipment

                            1 pass of
                           equipment
                              Water content, %
                   At this point, the sample has had
                   most of its air driven out by the
                   compaction
Dry Density, pcf



                         10 passes of
                          equipment


                                   100 %
                               saturation line




                              Water content, %
                     At a lower water content, energy
                     has little effect on the compacted
                     density of a clay soil
  Dry Density, pcf




10 passes of
   4 passes of
 equipment of
   3 passes
   equipment
   equipment
   2 passes of
   equipment
   1 pass of
  equipment
                               Water content, %
Compacting at low water contents

 Atlow water contents, insufficient
 water is available to lubricate the
 particles and allow them to be
 rearranged into a dense structure.
 The frictional resistance of dry
 particles is high
                    At a very high water content,
                    energy has little effect on the
                    compacted density of a clay
                    soil because the water is
Dry Density, pcf



                    incompressible and takes the
                    applied force without
                    densifying the soil

               This results in a term            103passes of
                                                   4 passes of
               called pumping                     equipmentof
                                                    equipment
                                                   2 passes
                                                    equipment
                                                    1 pass of
                                                   equipment
                                   Water content, %
Compacting Very Wet Soil

At this point, few air
  pockets remain –
 compaction forces
are carried by water
   in soil which is
   incompressible
Water has Zero Shear Strength
Water has Zero Shear Strength
Effect of Water Content

 Now   examine the effect of just changing the
  water content on a clay soil, using the same
  energy each time the soil is compacted.
 For example, assume soil is spread and
  compacted with 4 passes of a sheepsfoot
  roller each time.
 Examine using State Diagram
                   Effect of Water Content
Dry density, pcf




                    99.0
                    pcf
                                   Sample 1 compacted at 12 %
                                  water – Dry Density is 99.0 pcf

                           12 %              Water content, %
            Effect of Water Content


                                   Sample 2 compacted at
Dry density, pcf




                                  14 % water – Dry Density
                   104.5                is 104.5 pcf
                   pcf




                           14 %         Water content, %
            Effect of Water Content
Dry density, pcf




                   105.5
                   pcf
                                                       Sample 3
                                                     compacted at
                                                     16 % water –
                                                      Dry Density
                                                      is 105.5 pcf


                           Water content, %   16 %
            Effect of Water Content
Dry density, pcf




                                    Sample 4
                                 compacted at
                                 18 % water –
                                  Dry Density
                                   is 98.5 pcf
                   98.5
                   pcf


                          Water content, %       18 %
            Effect of Water Content @ constant
            energy
Dry density, pcf




                    Maximum
                   dry density,
                       pcf

                                       Optimum water
                                         content, %
                    Water content, %
            Now, perform the same test at a
            different (Higher energy) on the soil
                                         10 passes of
                                          sheepsfoot
                                            roller
Dry density, pcf




                                       4 passes of
                                       sheepsfoot
                    Water content, %      roller
            Effect of Soil Type on Curves

                            Plastic Clay Soils have Low
                            Values of Maximum Dry
Dry density, pcf




                   80-95
                            Density
                    pcf




                     Water content, %
            Effect of Soil Type on Curves

                      Plastic Clay Soils have high
                      values for optimum water
Dry density, pcf




                      content (20-40 %)



                                      20-40 %

                   Water content, %
            Effect of Soil Type on Curves

                         Plastic Clay Soils have a Flat
                         Curve for Lower Energies
Dry density, pcf




                         Density




                   Water content, %
            Effect of Soil Type on Curves
                   115-135
                     pcf
Dry density, pcf




                     Sandy Soils with Lower PI’s
                     have High Values of
                     Maximum Dry Density



                    Water content, %
            Effect of Soil Type on Curves
Dry density, pcf




                   Sandy Soils with Lower PI’s have
                   Low Values of Optimum Water
                   Content

                                        8-15 %

                     Water content, %
            Effect of Soil Type on Curves
Dry density, pcf




                   Sandy Soils have a Steep Curve
                   – Short distance from plastic to
                   liquid states of consistency




                      Water content, %
                                                  Lower PI –
            Summary                            Sandier Soils in
                   110-135                       this Region



                                                  Intermediate PI
Dry density, pcf




                   95-120                           Soils in this
                                                      Region
                              Higher PI –
                             Clayey Soils in
                              this Region
                   75-95



                       Water content, %
                            Lower PI –
            Summary      Sandier Soils in
                           this Region

                                     Intermediate PI
                                       Higher PI –
                                       Soils in this
                                     Clayey Soils in
                                          Region
                                       this Region
Dry density, pcf




                           8-14     12-20    20-40
                   Water content, %
Family
of
Curves
(Covered
Later)
Family of Curves         Zero air voids curve
                         not parallel to line of
                          optimums at upper
                                 end



                              Line of
                             Optimums



      water content, %
Proctor’s principle of compaction

 Using a standard energy, if a series
 of specimens of a soil are compacted
 at increasing water contents, the
 resultant dry density of the
 specimens will vary. The density
 will increase to a peak value, then
 decrease.
Principle of Compaction

A  plot of the dry density versus the
  water content from a compaction test
  will be parabolic in shape.
 The peak of the curve is termed the
  maximum dry density, and the water
  content at which the peak occurs is the
  optimum water content.
Standard Proctor Energies

Several standard energies are used
 for laboratory compaction tests
 – Standard – 12,400 ft-lbs/ft3
 – Modified – 56,000 ft-lbs/ft3
 – California – 20,300 ft-lbs/ft3
Standard Proctor Compaction Test
Summary
                                      5.5 #
                                     hammer
 Uses  5.5 pound
  hammer
 dropped 12 inches
                                     12”drop
 mold filled in 3 lifts
 25 blows of hammer
  per lift                 3 lifts
 Total energy is
  12,400 ft-lbs/ft3
Modified Proctor Compaction Test
Summary
                                       10 #
                                     hammer
 Uses  10 pound
  hammer
 dropped 12 inches
                                     18”drop
 mold filled in 5 lifts
 25 blows of hammer
  per lift                 5 lifts
 Total energy is
  12,400 ft-lbs/ft3
Proctor Compaction Test Summary
        Standard molds are used
 Several
 depending on maximum particle size in
 sample
  – 4”diameter mold (1/30 ft3) used for soils
    with low gravel contents
  – Method A for soils with < 20 % gravel
  – Method B for soils with > 20 % gravel
    and < 20 % larger than 3/8”
Proctor Compaction Test Summary
        Standard molds are used
 Several
 depending on maximum particle size in
 sample
  – 6”diameter mold (1/13.33 ft3) used for
    soils with significant gravel contents
  – More than 20 % gravel larger than 3/8”
  – Must have less than 30 % larger than 3/4”
Proctor Compaction Test Summary

 Standardized  tests are not available for soils
  with more than 30 percent by weight of the
  total sample being larger than 3/4”in
  diameter gravels
 ASTM Compaction Test Methods are
  – D698A              D1557A
  – D698B              D1557B
  – D698C              D1557C
    Proctor Compaction Test Summary

   Prepare 4 to 5
    specimens at
    increasing water
    contents about 2 %
    apart. Example -
    prepared samples at
    14, 16, 18, and 20
    percent. Use range of
    moistures based on
    feel and experience.
Proctor Compaction Test Summary
                    Hammer
   Then, compact
    each sample
    into a steel
    mold with
    standard          Cured soil
    procedures
          Compaction mold
Proctor Compaction Test Summary

 Then, strike
 off excess
 soil so the
 mold has a
 known
 volume of
 soil.
Proctor Compaction Test Summary

 For each sample, measure the weight and the
  water content of the soil in the mold
 The mold volume and weight are
  pre-measured. Don’t assume nominal volume of
  1/30 ft3 or 1/13.33 ft3
 Calculate moist density
 Calculate dry density
 Plot dry density and water content for each point
Class Problem

 Calculate   Moist density, dry density
Class Problem
Mold wt = 4.26 #, Mold Vol. = 0.03314 ft3
Class Problem

Calculate   Moist density, dry density
Plotcurve of dry density versus
 water content
Determine Maximum dry density
 and optimum water content
   Set Up Plot – Form SCS-352

   110

  5
pounds
         {

    90
     Set Up Plot – Form SCS-352




Make each vertical division equal
  to 1 percent water content
Class Problem
 Calculate Moist density, dry density
 Plot curve of dry density versus water
  content
 Determine Maximum dry density and
  optimum water content
 Plot zero air voids ( 100 % saturation
  curve assuming specific gravity = 2.68
Zero Air Voids Curve
 After you plot a compaction test,
  plotting a zero air voids curve is very
  important. This curve is also called the
  100 % saturation curve
 This curve shows for a range of dry
  density values what the saturated water
  content is for any given value
Compaction Problem

         Zero air void equation
Assume 3 values of gd and calculate wsat%
    Assumed dry density = 105
                  assumed Gs = 2.70
              pcf      Unit wt. water = 62.4
                     100 % Saturation
                     Curve
                               95 % Saturation
                               Curve
                            wsat(%) = 22.1(%)


75 % Saturation
Curve
Zero Air Voids Curve
Plotted Class Problem
Zero Air Voids Curve
 The  100 % saturation curve is used to
  judge the reliability of the compaction
  curve and of field measurements of
  compacted soil density and water
  content
 Compacted soils for NRCS
  specifications are usually at a degree of
  saturation of about 75 to 95 percent
             100 % Saturation
             Curve

                         95 %
                         Saturation
                         Curve
75 %
Saturation
Curve
Review of Compaction

 Evaluating   Compaction Tests
  – Standard requirements - spread in
    water content about 2 % and at least
    two points above and below optimum
  – Typical shape - soil type ?
Compaction Problem


    Other given information:
    LL = 47, PI = 30,
    classified as CL soil
    Gs = 2.68
Evaluating compaction test



                         2.7 %
           2.1 % 2.7 %




       Are points about two percent apart ?
Evaluating compaction test




       Are two points below and 2 above
                  optimum ?
  Review of Compaction
                        Optimum w% = 21.0 
Optimum water content
 about 80 % saturated        % sat = 21.0÷23.6=89%
 water content ? -
 Acceptable range is    102.5 pcf

 75-95
Plotted Class Problem
                        wopt/wsat =
                     21.0/23.6 = 89 % 




               wsat @ 102.5 pcf =
       (62.4/102.5 - 1/2.68) * 100 = 23.6 %
   Review of Compaction
  Wet side parallel to
   saturation curve at 
   90 % saturation ? % Sat = 24.3 ÷ 26.4 =
                                         92.0 %


                               gd, pcf
Check a point on wet side at
  98 pcf, w % on curve is
           24.3%


                                                  w, %
Plotted Class Problem



                                 wopt/wsat =
                              24.3/26.6 = 91 % 



              wsat @ 98.0 pcf =
     (62.4/98.0 - 1/2.70) * 100 = 26.6 %
Review of Compaction

 Evaluating Compaction Tests
   Typical value for fine-grained soils
     compared to Navdocks equations

   gdmax = 130.3 - 0.82 *LL + 0.3*PI

   wopt = 6.77 + 0.43 * LL - 0.21 * PI
Review of Compaction

 Evaluating Compaction Tests
    Typical value for fine-grained soils
      compared to Navdocks equations
   gdmax = 130.3 - 0.82 *47 + 0.3*30
         = 100.8 pcf
   OK - test value was 102.5 pcf
   wopt = 6.77 + 0.43 * 47 - 0.21 * 30
        = 19.6 %
   OK Test value was 21.0 %
Purposes of compaction
 Soilsare compacted to improve the
  engineering properties over those of
  loosely placed soils.
 The engineering properties are affected
  both by the density to which the soil is
  compacted and the water content at
  which it is compacted
         Role of compaction tests
           in earth fill projects
 Samples   are obtained in site investigation
  and sent to laboratory for testing
 Soils are tested to determine reference
  density - as well as other index properties
 Engineering properties are measured by
  testing at a percentage of the reference test
  density. For example, a shear test might be
  performed at 95 percent of the Standard
  Proctor maximum dry density of the soil.
            Role of compaction tests
              in earth fill projects
   The engineering properties are used in analyses
    to determine a suitable design
   For example, the shear strength is used in a slope
    stability analyses
   If the engineering properties allow a satisfactory
    design, then the degree of compaction is used in
    a contract specification.
            Role of compaction tests
              in earth fill projects
   If an unsatisfactory design results, the soil is re-
    tested at a different degree of compaction to
    obtain better engineering properties
   The design is re-analyzed and the process
    repeated until a final satisfactory degree of
    compaction is decided
   Then the degree of compaction is used in a
    contract specification.
           Role of compaction tests
             in earth fill projects
   Quality control processes are used to ensure that
    the earth fill is compacted to the degree of
    compaction specified, within a range of specified
    water contents
   Field compaction tests are performed to assure
    that the proper reference density is being used
Compaction
Tests as
Used in
Design of an
Earth Fill
Example of Process

 Sample   obtained to determine suitability as
  clay liner
 Sample Sent to Laboratory
 Laboratory performs Standard Proctor Test
 A Permeability Test is performed at 95 % of
  maximum Standard Proctor Dry Density
Example of Process

 The  sample is remolded at 2 percent wet of
  optimum (for this sample, 85 % saturated)
 The permeability test measures an
  acceptably low permeability
 A recommendation is given to the field
  office that compaction to this combination
  of density and water content results in
  acceptably low permeability
Example of Process

 During  construction, measurements of dry
  density and water content are made during
  construction.
 If the degree of compaction and percent
  saturation are equal to or better than
  specified, the liner is judged to have a low
  permeability and is considered acceptable.
Class Problem 2
A   compaction test measures a maximum
  dry density of 104.0 pcf and an optimum
  water content of 18.0 %. The soil has an
  estimated Gs value of 2.68
 A contract requires compaction to 95 % of
  maximum dry density at a water content
  of optimum or greater
Class Problem 2
 A field test measures a moist density of 126.3
  pcf and a water content of 23.4 %
 Does the compacted fill meet the contract
  requirement ?
 Use the values given for measured moist
  density and water content, calculate the dry
  density
 Assume a Gs value of 2.68 and compute a wsat
  value
  Class Problem
 Compare    the reported compaction water
  content to theoretical saturated water content
 Compacted soils are commonly in the range of
  75-95 percent saturated
 What do the results tell you about the
  reliability of the field data?
 What would you look for to explain any
  problems?
Conclusions of Class Problem

 The  measured data appears to have
  problems.
 Possible errors are in the measurement of
  the dry density, the water content, or the
  specific gravity value used in computations
 Recommend investigating most probable
  causes

				
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