Excavation Safety

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Excavation

A man made cavity, depression or trench made by earth Removal.

 Types of Excavation:

1. Manual Excavation: without using   powered equipment

2. Mechanical Excavation: The excavation   work using Electrical or mechanical      

    Equipment. 

 Hazards of Excavation: 

1. Collapse of walls of excavation (Cave in)
2. Hitting by underground utilities (electrical cables, telephone cables, pipeline) 
3. Presence of toxic gases 
4. Falling of person/vehicle 
5. Falling of material 
6. Flooding of water accumulation 
7. Unstable Adjacent Structure 
8. Improper access and egress 
9. Lack of Oxygen in deep excavation

 Controls of Excavation: 

1. Permit to work 
2. Authorization 
3. Area survey report (Use Cable detectors, service plan, trial pits to avoid underground utility) - duly signed by the Surveyor and HSE 
4. Soil testing (According to which protective system must be employed) 
5. Method Statement
6. TRA 
7. Maintain distance from Adjacent structures 8. Vehicle Pathway should be provided (Gaarri) - 25ft 
9. Hard Barrication Mum
10. Safety signage 
11. Flickering/Flashing signs 
12. Protective system like shoring, sloping, benching whenever the depth is greater than 1.5 m (5ft) 
13. Access every 7.5m
14. Scaling/Clearance 1m-store material away from all the edges
15. Supervision 
16. Wind speed less than 20 knots 

Protective system shall be employed whenever depth exceeds 1.5 m/5 feet 

• Heavy machinery shall be kept 3 meters away from excavation 
• Whenever depth Greater than 1. 2 m ladder shall be provided every 7.5m distance. And if depth is less than 1.2 m excess ladder should be installed at every 30m.
• Ladder must be 1m above the excavation  Mechanical Excavation shall not be used within 3 meters any underground obstruction 
• No mechanical Excavation closer than 5 meters to any hydrocarbon carrying pipeline. 
• W/D less than 2 is confined space Download HSE Docs hseprof.com Protective Systems for Excavation: As soon as excavation reaches 1.5 meters protective system should be employed that shall be based on the evaluation of;

• Potential depth of the excavation 
• Possible variation in water content of the material being excavated while the 
• Excavation is open. 
• Loading imposed by structures, equipment, overlying material, or stored material;
• Vibration from the equipment, blasting, traffic, or other sources. 

Types of Protective Systems: 

Shoring 

A structure that supports the sides of excavation and protect against cave-ins.

Sloping 

A technique in which sides of excavation are inclined to a specific angle.

Benching

A technique in which sides of excavation are excavated in one or a series of horizontal steps having vertical depression. Types of Soil: Compressive strength: Resistance of a material to breaking. 

Types of Soil: 

Compressive strength: Resistance of a material to breaking. 

Rock type

•  90 Degree Slope 

Type A:  

• Compressive strength is 1.5 tons per square foot or more 
• Highly cohesive 
• Clay, sandy clay 
• 53 degrees slope 

Type B: 

•  CS between 0.5-1.5 tons/square feet 
•  Medium Cohesive  Gravel and silt 
•  Sloping angle is 45 degrees 

Type C: 

•  CS less than 0.5 tons /square feet 
•  Least cohesive 
•  Sand 
•  34 degrees sloping angle 

Trench: 

A narrow excavation, where depth is greater than width. (Width should not be greater than 4.5 meters/15 feet)  

• Any trench having depth greater than 1.2 meter is considered as Confined space.  
• For stable Rock type sloping angle should be 90 degrees. 

Inspection of Excavation: 

• Start of every shift or work 
• Environment change, heavy vibration changes the strength and stability of soil 
• Accidental fall of rock, sand or material 
• Every 7 days for open excavation