Excavation
Safety
v
Excavation
is any man-made cut, cavity or
depression in an earth surface
that is formed by earth removal.
Trench
is a narrow excavation where the
depth is greater than its width, and
the width measured at the bottom
is not greater than 15 ft.
Hazards of Excavation Works
Soil Collapse
Falls
Vehicular Traffic
Underground Utilities
Working Surface
Confined Space
Conditions
Principal Causes of Soil Collapse
Steep cutting angle
Super imposed load
Shock & Vibration
Water Pressure
Drying
Mechanics of Soil Collapse
Soil Collapse
Prevention of Soil Collapse
Type A Most stable: clay
Type B Medium stability: silt and unstable
rock (disturbed soil as type B)
Type C Least stable: gravel, loamy sand,
submerged soil, soil from which water is freely
seeping.
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Prevention of Soil Collapse
Cut the slope at a safe angle (H:V)
Type A - 3/4:1 or 53
Type B - 1:1 or 45
Type C - 1 :1 or 34
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Prevention of Soil Collapse
Provision of shoring and timbering
v
Sheet Piles
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v
Plate Lining System
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Box Type
Shielding
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Prevention of Soil Collapse
Per Rule 1413 of the Occupational
Safety and Health Standards (OSHS):
The walls of every excavation over 1
meter deep shall be supported by
adequate shoring
Falls
Falls
Minimum Berm
- not less than one third of the depth of
the excavation
- may be reduced to not less than 1 meter
provided that materials are stable,
shoring and barriers are present
(Per Rule 1413 of the OSHS)
Falls
Barricades of at least 1
meter high should be
provided.
Signs should be posted
to prevent the public
from going near the
excavation.
Surface Crossing of Trenches
Walkways or bridges
must be provided
Minimum clear width
of 20 in.
With standard rails
Extended a minimum
of 24 in. past the
surface edge
Vehicular Traffic
Provide workers with
warning vests or other
suitable garments marked
with reflectorized materials
Designate a trained
flagperson along with
signs and barricades when
necessary
Use horn or give signals to
ensure safety.
Underground Utilities
Determine location of
underground facilities and
take necessary steps to
prevent damage to these
facilities.
In an open excavation,
support, protect or
remove underground
installation.
Working Surface
Excavation shall be
kept free of water at all
times
And in muddy area,
workers should be
provided with boots to
reduce the hazard of
slipping.
Groundwater Control
Sump Pumping
Well Pointing
Well Pointing
Single-sided Well Point
Double -sided Well Point
Confined Space Conditions
Hazardous Atmosphere:
Oxygen, O2 : < 19.5% or > 23.5%
Flammable gas concentration > 10% of
Lower Flammability Limit (LFL)
Hazardous toxic chemicals
Confined Space Conditions
Excavation in confined space
Check the condition of the atmosphere
before entry
Do not work alone in a confined space
Provide lifeline
Provide ventilation or blower before entering
Provide emergency rescue equipment such
as breathing apparatus, safety harness and
line and basket stretcher
Ingress and Egress
(Ladder)
Ingress and Egress
(Ladder)
Working in Excavation
Prior to opening
Check excavation permit
Identify all underground installations
Remove trees, boulders, stumps, other
surface encumbrances and hazards before
starting excavation
Working in Excavation
During operations
Wear appropriate PPE
Give special attention to side slopes that
are adversely affected by weather,
moisture content or vibration
Safe working distance between workers
Maintain guardrails, fences, or other
barricades and warning lights
Working in Excavation
During break time, workmen should never
stand or take rest on high banks of soft
material
Do not leave tools, materials, or debris in
walkways, ramps, or near the edge of
excavations
Do not use guardrails as resting place
Inspection
Daily before start of each shift
After heavy rain
When fissures, tension cracks, undercutting,
water seepage, bulging at the bottom or other
conditions occur
When there is any indication of change or
movement in adjacent structures or spoil pile
Rule 1413 of the OSHS states that excavation
shall be inspected at least once everyday.
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Summary
Remember:
An excavation may not be safe to enter without a
proper support structure being provided.
Back-filled ground are especially dangerous.
Water increases the possibility of a cave in.
Excavation should be considered as a confined
space.
A worker does not have to be completely buried in
soil to be seriously injured or killed.
Have a nice week!!!
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