Shoring
Shoring uses structures such as a metal hydraulic, mechanical or timber shoring
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system that supports the sides of an excavation. It is designed to prevent cave-ins.
In fact, sheet piles are also a form of shoring. After the excavations are completed, take special precautions to prevent injury from cave-ins in the area between the excavation wall and the foundation wall:
▪ Protect the depth of excavation against cave-ins.
▪ Keep the horizontal width of the excavation to make sure that work activity
would not vibrate the soil while workers are in the trench.
▪ Plan the foundation work to minimize the number of workers in the trench and
the length of time they spend there.
▪ Inspect the trench regularly for changes in the stability of the earth (water,
cracks, vibrations, spoils pile).
▪ Stop work if any potential for cave-in develops and fix the problem before
work starts again.
For safe trench excavation, adequate support must be installed ahead of excavation as far as is practicable.
“The contractor responsible for any construction site at which excavating or
Earth working operations are being carried on shall cause a structure made of suitable timber or other suitable material to be erected in connection with the operations as soon as may be necessary after their commencement so as to prevent workmen employed on the site from being endangered by a fall or displacement of earth, rock, or other material (including waste material and debris) adjacent to or forming the side of the excavation or earthwork.”
Specific design with details of shoring complete with drawings should be prepared for excavations with particular attention to:
▪ the depth of the excavation, and
▪ possible effects affecting roads, buildings, structures, slopes, services of
adjourning areas, from the base of the excavation to the ground surface, and should be carried out by a professionally qualified engineer who is competent
in carrying out a proper shoring design.
General precaution for safe excavations
▪ Shoring in place and in sound condition
▪ Excavation well secured
▪ Signage displayed
▪ Banks battered correctly and spoiled away from edge
▪ Clear and safe access to excavation
▪ Separate access and egress points from excavation
▪ Safe work procedure in place
Points to discuss at the initial planning meeting:
▪ Find the location of all underground utilities by contacting the local utility
companies to identify and locate the services before digging.
▪ Keep workers away from digging equipment and never allow workers in an
excavation when equipment is in use.
▪ Keep workers away from space between equipment in use and other
obstacles and machinery that can cause crushing hazards.
▪ Keep equipment and the excavated dirt (spoils pile) back 2 feet from the edge
of the excavation
▪ Have a competent person conduct daily inspections and correct any hazards
before workers enter a trench or excavation.
▪ Provide workers with a way to get into and out of a trench or excavation such
as ladders and ramps. They must be within a reasonable distance from the
workers.
▪ For deeper excavations and utility trenches, use shoring, shields (trench
boxes), benching, or slope back the sides. Refer to the result of soil analysis
to determine the earth’s safe slope angle.
▪ Keep water out of trenches with a pump or drainage system, and inspect the area for soil movement and potential cave-ins.
▪ Keep drivers in the cab and workers away from dump trucks when dirt and
other debris is being loaded into them.
▪ Don’t allow workers stay under any load and train them to stay clear of the
back of vehicles.
The statutory requirements on the use of excavators in construction work are clearly laid down in the ‘Code of Practice - Safe Use of Excavators’ issued by the
Commissioner for Labour.It covers details on the safe use and operation of
excavators for excavation and earth moving operations, including the safe use of bucket attachment.
Access/egress
Proper planning of access and egress, including rescue in case of emergency, is very
important. Access to the surface should be by means of:
▪ ladders;
▪ stairways; or
▪ ramps.
In trenches, access ladders should be spread out at intervals and at locations workers
are working and near the trench.
Normal access routes used within an excavation should, whenever practicable, permit
workers to pass along without bumping into obstructions or being hit by debris.
Walking in an excavation should be made possible by secure footing without risk of
falling.
In situations where an excavation or trench is heavily timbered and where headroom
is limited, access to and from work should be along well-defined routes which can be
protected more readily and the use of other routes should not be permitted.
Separation of traffic Wherever practicable, the route used to bring out excavated material should be separated from that used by the workers. In a small shaft or drive where it is not possible to provide separate routes for the two kinds of traffic, the movement of workers should be forbidden while excavated material or plant is being
moved and vice versa.
In shafts shallow enough for workers on top to see and talk to the workers below, no difficulty should arise, but in shafts of intermediate depth, in which the
workers have to climb up and down the ladders, there is need for an effective signaling system and there may be a requirement for automatic locking of winding gear while workers are moving. Where mechanical haulage is used in small drives, manholes or refuges should be excavated into the side of the drive to provide shelter from passing
traffic. Such refuges should be of a reasonable size and appropriately spaced on the same side of the drive.
Secure footing
This is essential for safe access. Loose stones and large rock projections should be removed and in some cases it may be necessary to provide a timbered walkway to ensure safe walking. Accumulations of mud should be prevented and sloping walkways should be cleared or otherwise made slip-proof.
Adequate lighting
Where daylight is insufficient shafts, drives, trenches and open excavation should be provided with adequate lighting. Glare should be guarded against because contrasted with a deficiency of light, it increases considerably the risk of falls from slipping
or tripping.
Protection from falls
Where there is a risk of any person falling from an access way, a handrail, and sometimes an intermediate rail or a toe board, should be provided to enable persons to pass more easily and to prevent falls. At any landing, the ladder below should be
offset from the ladder above so that it is not possible for a person or articles to fall past the landing. Landing platforms should be fitted with guard rails and toe boards.
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