Different types of hazards are associated with excavation of soil. for instance, failure of soils at sides of trenches and pits, movement of buildings due excavations at its vicinity, falling workers into pits, buried workers due to collapse of earth, cave-in which may cause suffocations of labors and etc. These hazards should be identified and preventive measures should be taken to avoid any accident at construction sites.
Excavation Hazards- Affects and Prevention Measures
1. Pit Excavation up to 3m
Pits up to three meters may be
excavated for testing subsurface soil, monitoring water table, foundation
construction etc. There are number of hazards which may be encountered in
excavations of pits up to 3m depths. These hazards, their effects, and preventions
measures are summarized in Table 1.
Table 1 types of hazards related
to pit excavation with a depth of up to 3m plus their influences and prevention
measures
| Type of hazard | Effects of hazard | Preventive measures |
| Falling into pit |
Personal injury |
Provide guard rails / barricade with warning signal, provide minimum two entries / exits, Install escape ladders |
| Earth collapse | Suffocation /breathlessness, Buried |
Employ suitable size of shoring and strutting if required, keep soil heaps away from the edge equivalent to 1.5m or depth of pit whichever is greater. Do not allow vehicles to operate too close to excavated areas. Maintain at least 2m distance from the edge of cut. Maintain sufficient angle of repose. Provide slope not less than 1:1 and suitable depth of excavation in all soils except hard rock. Battering / benching sides. |
|
Contact with buried electric cable, Gas / Oil Pipelines | Electrocution, and Explosion |
Obtain permission from competent authorities prior to excavation if needed. Locate the position of buried utilities Start digging manually to locate the exact position of buried utilities and thereafter use mechanical means. |
2. Pit Excavation Beyond 3m
This type of pit with such depth might
be employed for the construction of foundations of multi-storey buildings in
which basements and located, it may also be employed for other applications as
well. Hazards associated with pits deeper than 3m meters along with their
influences and prevention strategies are presented in Table 2.
Table 2 hazards related to excavation of pits
deeper than 3m, their effects and prevention strategies
| Type of hazard | Effects of hazard | Preventive measures |
|
Hazards related to pits up to 3m plus flooding due to excessive rain / underground water |
cause drowning situation |
Prevent ingress of water, Identify and provide suitable size dewatering pump or well point system |
|
Digging in the vicinity of existing building / structure |
Building / structure may collapse, Loss of health and wealth |
Obtain prior approval of excavation method from local authorities. Use under-pinning method. Construct retaining wall side by side. |
|
Movement of vehicles / equipment close to the edge of cut. |
cause cave-in or slides, workers may get buried. |
Barricade the excavated area with proper lighting arrangements. Maintain atleast 2m distance from edge of cut and use stop blocks to prevent over-run. Strengthen shoring and strutting |
3. Narrow and Deep Excavations
This particular type of excavation is
commonly used for pipelines and it may be use for other applications as well. Table
3 provides different hazards, effects, and prevention measures related to
narrow and deep excavations.
Table 3 hazards related to narrow and deep
excavations along with their influences and preventive measures
| Type of hazard | Effects of hazard | Preventive measures |
|
Pits related hazards plus frequent cave-in or slides |
Cause severe injuries or prove fatal. |
Battering / benching of sides. Provide escape ladders. |
|
Flooding due to hydro-static testing |
Arise drowning situation |
Battering / benching of sides. Provide escape ladders. Bail out accumulated water. Maintain adequate ventilation. |
4. Rock Excavation by Blasting
Hazards and risks caused by rock
excavation by blasting is presented in Table 4.
Table 4 hazards associated with rock excavation by
blasting and their influences plus preventive measures
| Type of hazard | Effects of hazard | Preventive measures |
| Improper handling of explosives |
May prove fatal |
Ensure proper storage, handling and carrying of explosives by trained personnel. Comply with the applicable explosive acts and rules. |
| Uncontrolled explosion |
Can cause severe injuries or prove fatal. |
Allow only authorized persons to perform blasting operations. Smoking and open flames are to be strictly prohibited. |
|
Scattering of stone pieces to atmosphere |
Can hurt people |
Use PPEs like goggles, face mask, helmets etc. |
| Entrapping of persons / animals |
May cause severe injuries or prove fatal |
Barricade the area with red flags and blow siren before blasting. |
| Misfire |
May explode suddenly |
Do not return to site for at least 20min or unless announced safe by designated person. |
5. Excavations and Pile Works
Hazards that may be caused by
excavations and installations of pile are provided in Table 5.
Table 5 hazards due to excavations and
installation of piles
|
Type of hazard |
Effects of hazard |
Preventive measures |
|
Failure of pile-driving equipment | Can hurt people |
Inspect piling rigs and pulley blocks before the beginning of each shift/ |
|
Noise pollution | Can cause deafness and psychological imbalance. |
Use personal protective equipment like ear plugs, muffs etc. |
|
Extruding rods/casing | Can hurt people |
Barricade the area and install sign boards Provide first aid |
|
Working in the vicinity of live-electricity | Can cause electrocution / asphyxiation |
Keep sufficient distance from live electricity as per relevant standard codes. Shut off the supply if possible. Provide artificial / rescue breathing to the injured. |