Summaries - Trench Cave-ins
An excavation is any man-made cut, cavity, trench, or depression in the ground, formed by the removal of earth. A trench is an excavation that is deeper than it is wide.
Cave-in in an excavation is the detachment of the mass of soil in the side of a trench and the sudden displacement of the soil inside the excavation, which represents a hazard to the person inside. Several techniques are used to minimize the likelihood of cave-ins, including sloping, shoring, and shielding.
Some reasons for excavation are:
- The top soil may not be suitable for construction like mineral matter, organic matter, water, etc.
- an excavation may be needed for construction work to support a structure and its foundations.
There are preparatory issues that need to be considered such as the type of excavation and the appropriate equipment/ method of carrying out the excavation.
Decisions have to be made about the exact depth of digging for example and the protection of sides and shores to prevent any side collapse. Also, you must make decisions about specified locations marked to deposit or dump the surplus earth
Types of excavations:
1. Confined/ structural excavation - for individual foundations and trenches
2. Bulk excavation - quantum of excavation is voluminous and done with several versatile earth-moving machineries
3. Excavation in Rocks
Before starting to dig, the following must be done
Provide a sufficient number of notice boards and danger signals to prevent accidents.
Provide barriers or coverings to excavations, shafts, pits, and other openings having a vertical fall distance of more than 2m.
Fencing should also be erected for deep excavations and where there is a likelihood of the public frequenting the area.
Also before excavation commences:
Utilities must be exposed before digging
Work permits shall have been secured from the owner of the utility for emptying, diverting, and de-energizing.
Workmen should wear safety shoes, gloves, etc
Precautions for adjacent structures must be taken when excavating.
Site Clearance should be carried out before digging begins.
Hazards must be removed/ supported before excavation starts
Excavation sites must be protected, supported to safeguard employees.
An excavation is any man-made cut, cavity, trench, etc formed by earth removal. Excavations can include a building basement, roadbed, or trench.
A trench is a narrow underground excavation that is deeper than its width and no wider than 15 feet
Trench cave-ins are fatalities of excavations. it is a major killer in construction
A cave-in is a major hazard of excavation.
Design of Protective Systems
The employer shall select and construct
- slopes and configurations of sloping and benching systems
- support systems, shield systems, and other protective systems.
- shields - these can be permanent or portable,
- Shoring - such as a metal hydraulic, mechanical, or timber shoring system that supports the sides.
Inspection of Excavations
A competent person must make daily inspections of excavations, areas around them, and protective systems.
Before work starts and needed.
After rainstorms, high winds or other occurrences which may increase hazards.
When you can reasonably anticipate an employee will be exposed to hazards.
Excavating Equipment includes backhoes, drag-lines, shovels, and clam-shells. Also, others are: Earth Moving Machinery - power shovels, boom, bucket or grab, bulldozer
Falls of persons and materials.
Hard barriers, warning signs, and warning lights, and light reflectors shall be provided to prevent the fall of persons/ vehicles inside.
A cross-over bridge with a guard rail shall be provided across the trench for the local people and animals
Ladders shall be used to enter or leave the excavation
Fall of vehicles / Equipment
Heavy equipment and vehicles shall be kept back from the excavated sides at a distance not less than the depth of the trench
Adequate and well-anchored stop block shall be provided on the surface to prevent operating vehicles from falling accidentally into the excavation pit.
The trench shall be provided with a hard barricade
Waring light/ light reflectors shall be provided to warn the vehicle drivers at the night.
All vehicle and machine glass must be kept clean for visibility.
Transporting machinery are tractors and dumpers.
Tunnel construction is an underground passage provided beneath the earth's surface or water.
Examples of confined spaces are a tank, manhole, a well, cold storage, culvert, pipeline or vault, tunnel, and so on.
Some dangers in confined spaces are:
- lack of oxygen or even high dosage of oxygen.
- toxic atmosphere temperature
- extremes fire and explosion
- uncontrolled energy collapse of solids or liquids
To work safely in confined spaces, it's important to plan for standby workers and rescue operations.
Prepare personal protection devices such as respirator protective clothing and lifeline safety harnesses.
Attendant and rescue equipment should be placed outside the confined spaces.
Always review communication procedures and update them regularly.
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