SHORING AND TRENCHING SOIL CLASSIFICATION MANUAL TEST
SAFETY PRACTICE COMPLIANCE PROCEDURE B9 Classifying the stability of the soil you’ll be excavat- You must test the...
ing is an important part of all site evaluations. Soil
• PLASTICITY. Mold a
must be classified by at least one visual analysis and
damp sample of soil into a
T renches and excavations are some of the most hazardous construction
work sites. If you are digging an excavation more than 1.25 meters deep,
possibly less if there is a chance of ground movement, you must be protected
one manual test. That classification will determine
the degree of sloping and the type of shoring you
must use to protect yourself and coworkers from an
ball and try rolling it into
threads as thin as 3mm in
diameter. Cohesive material
by sloping or shoring the excavation. Short-cutting excavations can cost you accident in the excavation. can perform this test.
SOIL TYPES • PENETRATION. Press your thumb into
This safety practice summarizes safety guidelines on shoring and provides
Soil is divided into three classes. They are listed undisturbed soil as soon as possible after it has
information on the proper way to excavate and shore safely. been excavated. Type A soil can be indented, but
here from most stable to least stable.
Here are some terms you should be familiar with before starting any excava- with great effort. Type C soil can be indented
tion. easily and molded with light finger pressure.
Type B soil is that which doesn’t easily meet
BENCHING Type A or C requirements.
cohesive soil-clay, sandy clay,
A method of pro-tecting yourself from cave-ins • DRY STRENGTH. Dry soil that crumbles
by digging the sides of an excavation to form one under light pressure is granular. If it falls into
or more steps. TYPE B clumps, and the smaller clumps break with
difficulty, it may be clay.
less-cohesive soil, crushed rock,
silt, silt loam, sandy loam, previ- GENERAL EXCAVATION REQUIREMENTS
A horizontal member of a shoring system installed at a 90° angle to the sides of ously disturbed soil, unstable rock.
the excavation. It’s ends are placed in contact with vertical rails or wales. The following general excavation requirements
TYPE C suggest what to look for and how to prepare for an
SHEETING excavation before you even start to dig. They must
non-cohesive soil-gravel, sand,
be observed in every excavation in order to elimi-
A plywood member of a shoring system that holds back the soil on the sides of loamy sand, soil from which
nate potential danger to you and your coworkers.
an excavation and is supported by other members of a shoring system. Closed water is seeping.
sheeting means the plywood sheets are butted together. • Locate underground
VISUAL ANALYSIS utilities before you dig.
VERTICAL RAIL You must examine... Check with utility
companies to find out
Vertical member of a shoring system placed in contact with plywood sheeting
• soil in the excavated material for particle size and where cables and lines
and cross braces.
cohesive appearance. A fine grain texture is may be buried. Once
more cohesive than a coarse uncovered, you must
WALE grained texture. support, protect or
A horizontal member of a shoring system placed in contact with plywood remove the lines.
• material as it is excavated for
sheeting and cross braces.
cohesive clumps or granular • Test hazardous atmospheres as outlined in
clumps that break up. Safety Practice B7, “Confined Space”. You must
• open trenches for wall slough- conduct tests in any excavation that could contain
One who can identify existing and future hazards in the work area, and has the low oxygen levels or
ing or tension cracks.
authority to take immediate actions to eliminate other dangerous
those hazards. • area near the excavation for utilities that indicate conditions such as
disturbed soil. landfills or environmen-
HAZARDOUS ATMOSPHERE • excavation and surrounding area for seeping tal projects. Remove
Any atmosphere that could cause death, illness or water or high water table. water accumulation
injury because it is explosive, flammable, poison- from an excavation
• excavation area for vibrating sources that can before entering.
ous, corrosive, oxidizing, irritating, oxygen defi-
affect soil stability.
cient, toxic or otherwise harmful.
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• Wear reflective vests or other highly visible the top of the hole or trench to keep rocks and • Type A soil-maximum allowable slope 1:1 (45°) DON’T FORGET!
material when near equipment, trucks and cars. debris from falling in on yourself or coworkers.
• Type B soil-maximum allowable slope 1:1 (45°) • Remove shoring from the bottom up.
Remember to post signs, barricades and flag
persons as necessary. • There can be no soil showing between plywood • Type C soil-maximum allowable slope 1 1/2:1 • Pull sheeting out from above.
sheeting when shoring an excavation. (34°)
• Avoid falling objects by staying away from any • Back fill the excavation immediately after the
load being lifted. Always wear your hard hat, support system is removed.
• Use only hydraulic shoring or trench jacks (cross-
safety shoes and safety glasses while on or near
braces) when shoring any excavation. When • Don’t take short-cuts.
a job site.
using trench jacks, substitute a5 X 15 cm for a
There are tables available that can provide you with
• Construct temporary cross-overs where vertical rail. When using hydraulic shoring, raise
employees, pedestrians or equipment must cross more detail on how to shore properly. You must
the pressure to 3000 PSI as shown on the
over excavations. Cover or barricade all wells, know the soil classification, depth and width of the
hydraulic pump gage.
pits and shafts when the down-hole job is fin- excavation in order to use them. If you have any
ished. questions, see your supervisor.
SPACING OF VERTICAL RAILS
• Store spoil piles or
excavated material at • No more than1.8 meters apart
You are responsible for your own safety as well as
least1meter from the • No more than 1 meter from the bottom of the that of your fellow workers. Your decisions make
edge of an excavation. excavation
Don’t let it collect near
DID YOU KNOW? the difference between a job well done and a life
wall sides. • 90% of excavations are 1.5 to 3 meters deep.
• Protect the excava- • 85% of deaths from occur in 1.5 to 3 meters
tion edge whenever equipment is moving in the excavation cave-ins.
YOUR SAFETY IS OUR
area. Use stop logs, barricades and employee • Cave-in accidents are much more likely to be
spotters. NUMBER ONE CONCERN
fatal than other construction-related accidents.
• Provide access into
and out of an excava-
tion four or more feet
deep with a ladder or
ramp. You should be no
more than 8 meters from
a ladder or ramp at all SPACING OF CROSS BRACES AND WALES
times in an excavation. • No more than 1 1/2 meters apart vertically
Ladders must be secured from sliding or kickout,
and ramps can be at an incline of no more than • No more than 1 meter from the bottom of the
• Perform daily inspections with a competent • No more than 1/4 meter from the top of the
person who is qualified to identify potential excavation
hazards in an excavation. You may need more SLOPING
than one inspection in the same day if it rains or
other conditions change.
SLOPING AND SHORING GUIDELINES
Unless you are excavating less than 4', you must use
a protective support system for the walls of an
excavation. Overlooking any of the following
guidelines or conditions can cause a cave-in.
• Use 2 cm plywood against excavation walls,
leaving approximately 30 cm of plywood above
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