Excavation

Definition

“Digging and removal of earthen or rock from ground is called excavation”. 

OR

“Any man-made cut, cavity, trench or depression in an earth surface, formed by earth removal”.

‘Trench’ means a narrow excavation (as per its length) made below the ground whose depth is greater than the width, but the width of trench (measured at bottom) is not greater than 15 ft (4.6 m).

Excavation Hazards

Every excavation job needs proper planning and systematic execution. The serious hazards are: –

1. 

   Underground utilities,

2. Presence of toxic gases,
3. Nearby structures, building and their condition,
4. If excavation is like confined space (deeper),
5. Collapsing of excavation wall/cave-in,
6. Persons falling,
   
7. Falling object,
   
8. Collapse of loose soils,
9. Sudden inflow of water, etc.

Excavation methods

        1. Manual method:    Earth removed by person.

        2. Mechanical methods:      Earth removed by using equipment.

        Eg: Excavator, JCB.

Important safety facts are:

1. The area which needs to be excavated to be marked clearly with line, chuna or by other means.
2. Toolbox Talks to be conducted prior excavation.
3. Excavation plan should be made and discussed with all concerned and then approved. It must cover all aspects of excavation for example, type of soil, type of excavation – slopped, step, etc., excavation method – manual/mechanical, etc.
4. Process is called Trial Pits (for underground utilities). Location of underground water pipes, gas pipes, fuel pipes, storage tanks, electrical cables, telephone lines, should be ascertained (to find something out) by competent authority prior commencing excavation of area.
5. Suitable metal detector machines and adequate protection to be used to identify the underground services lines.
6. No shovel, crane or dragline should be used to excavate near electric lines before shutting off.
7. Excavation slopping or benching.
8. Excavation shielding or shoring.
9. Hard barricade and sign boards.
10. Gas testing as per guidelines.
11. Alternate access if excavation is near to road.
12. Avoid vehicle movements.
13. Create bund walls for preventing outside water from coming inside. Availability of DD pump for dewatering if flooding happens.
14. Confined space precautions if excavation becomes confined space.