1. EXCAVATION, LATERAL RESTRAINMENT FOR IT AND DEWATERING
Prepered By:
Alka Shah
Civil Engineering Department
Institute of technology
Nirma University

3. PRE REQUIREMENTS OF EXCAVATION

4. EXCAVATION
After setting out of foundation/building outline the next step is the excavation
Excavation can be done by manually or machines depends on type of excavation
Main excavation activity are:
Excavating top soil
Excavating trenches for foundation according to marking
Digging holes for piles
Digging out basement

5. EXCAVATION
Excavation can be done with reference to datum marked while setting foundation
Top soil should be remove because it contains vegetation which can damage foundation
Top soil then can be used for landscaping otherwise cleared away

6. Manual Excavation Equipment

7. Manual Excavation Equipment

8. Manual Excavation Equipment
For digging Borehole
Post hole auger
Helical auger

9. Manual Excavation Equipment
For digging Borehole
Manual but machine

10. POWER SHOVEL Excavation Equipment/Machines
OBJECTIVE: For digging and loading earth or fragmented rock and for mineral extraction

12. DRAGLINES OBJECTIVE: To lift heavy units in a site and swing it to the
required area/position.

13. CLAMSHELL ABOUT: The clamshell bucket is a more sophisticated
articulated several-pieces device, including two
elementary buckets associated on a hinged structure forming a claws-like appendage with an internal volume.

15. HOE
OBJECTIVE: To agitate land and move soil or similar matter from the ground

16. dredges
ABOUT: A dredger is any device, machine, or vessel that is used to excavate and remove material from the bottom of a body of water. For example, a scoop attached to the end of a
rope or pole by which a man can draw sediments up from
the bottom of a pond is a dredger.

17. LATERAL RESTRAINMENT FOR EXCAVATION

18. LATERAL RESTRAINMENT FOR EXCAVATION
Once exaction is over the two problems that contractor must solve for safety is
Supporting the sides
Removing water/Dewatering

19. LATERAL RESTRAINMENT FOR EXCAVATION
Supporting the side

20. Sides of excavation can be supported by following methods
LATERAL RESTRAINMENT FOR EXCAVATION:
Strutting/Timbering of trenches
Shoring
Scaffolding

21. Strutting/Timbering of trenches
Mainly for deep excavation

22. Methods of Timbering of Trenches
Stay bracing: To prevent the slip of earth in foundation trench
Used when excavation is to be carried out in moderately firm ground and depth does not exceed 2 m.
Vertical sheets or polling boards are placed opposite each other against the walls of trench
One or two rows of struts are used to held sheets in position.
Sheets are placed at an interval of 3 to 4 m and extend to the full depth of excavation.
Polling Boards – width 200 mm, thickness 40 to 50 mm
Struts – 100x100 mm for 2 m width trench
200x200 mm for more than 2 m width trench
Stay Bracing

23. Methods of Timbering of Trenches
2. Box sheeting: To prevent the slip of earth in foundation trench
Used when excavation is to be carried out in loose soil and depth does not exceed 4 m.
Box like structure – vertical sheets placed very near or sometimes touching each other and keeping them in position by longitudinal rows of wales with struts across the wales.
For very loose soil – vertical sheets are provided longitudinally supported by vertical wales and horizontal struts.
For more depth braces are provided along with struts.
Box Sheeting

24. Methods of Timbering of Trenches
3. Vertical sheeting: For deep trench in soft ground upto 10 m depth
Similar to box sheeting except work is carried out in stages.
At each stage, an offset is provided.
Vertical sheets, horizontal wales, struts and braces are provided.
Offset of 30 to 60 cm is provided at each stage for depth of 3 to 4 m.
Suitable working platform may be provided across the struts.
This arrangement is suitable for laying sewers and water pipes at considerable depth.
Vertical Sheeting

25. Methods of Timbering of Trenches
4. Runners: For extremely loose and soft ground which requires immediate support as the excavation progresses.
Runners – long thick wooden sheets or planks with iron shoe at one end.
Driven by hammering about 30 cm in advance of the progress of work.
Wales and struts are also provided.
5. Sheet piling: Used when (i) soil to be excavated is soft or loose (ii) depth of excavation is large (iii) width of trench is large (iv) presence of sub-soil water
Designed to resist lateral earth pressure and driven in ground by mechanical means
Runners

26. Precautions during Timbering
Slip of earth
Testing of struts
Sagging of wales
Movement
Removal
Safety helmets
Ladders
Traffic
Tools
Supervision
Adjacent structures
Fencing & Lighting
Spacing & Sizes of members