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

PRE REQUIREMENTS OF EXCAVATION

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

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

Manual Excavation Equipment

Manual Excavation Equipment

Manual Excavation Equipment For digging Borehole Post hole auger Helical auger

Manual Excavation Equipment For digging Borehole Manual but machine

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

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

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.

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

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.

LATERAL RESTRAINMENT FOR EXCAVATION

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

LATERAL RESTRAINMENT FOR EXCAVATION Supporting the side

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

Strutting/Timbering of trenches Mainly for deep excavation

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

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

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

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

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