Instruction for the Earthwork and Back filling Measurement takeoff

EARTHWORK AND BACKFILLING 

1. Block Levels have to be taken at the start of the work. The intervals can be of 3m or 5m.
2. The Uom is in CUM and should be rounded off to the nearest two decimals.
3. For Pit Excavation an offset of 30 cm can be taken on either side of the footing up to 1.5 m depth and for more than 1.5 m depth it can be taken as 50 to 60 cm.
4. For Pit, excavation Depth can be arrived by taking

                                                      = Average top-level – Average Bottom Level

5. For Mass Excavation Earthwork quantity can be calculated by using any of the rules like Trapezoidal or simsons rule etc. Proper CVI (Reasons) has to be maintained for Mass Excavation
6. For hard rock and soft rock, the top levels and bottom levels should be taken with consultant approval. Quantity can arrive with top and bottom levels or the quantity can be arrived by stacking the Hard rock. The place for stacking should be selected in accordance with clients’ approval and must be recorded with the joint measurement from the client and contractor.
7. Backfilling quantity can be arrived using trapezoidal or simsons rule.
8. The final quantity is arrived by deducting the volume of concrete and size stone masonry below ground level from the total quantity.
9. Earth brought from outside or to be carted away is calculated by

                                    = Total Excavated Quantity - Total Backfilling Quantity.

                If Value is  - Ve - It is Earth brought from outside

                                +Ve - It is Earth to be carted away.

10. For Jungle clearance item, the area to be considered is 5m offset all-round the building and if for road works, 1m offset should be considered on either side.
11. For EX:  The below is the block level of area 40 m X 20 m with levels of 5 m intervals with mass excavation to be done for the entire area with excavation bottom level as 95.2

block-level

The volume can be found by taking the average rectangle/square method. The depth of excavation               =(98.75+98.7+98.68+98.85)/4 – 95.2 (i.e. Avg Top Lvl – Bottom lvl.).

                        =  3.545 m

Area                  = 5 X 5 = 25 sqm

Volume of Earth = Area X Depth = 25 X 3.545 = 88.63 cum

      Similarly, the volume of Earth has to be calculated for Other Square areas and to be added to get the total quantity. If there is hard rock, it can be stacked separately. The volume of Hard rock stacked can be found by taking site measurements. For Ex, refer below sketch as stack measurement.

The Hard rock is stacked in the trapezoidal shape generally.

Stacked Quantity = H/3 (A1 + A2 + Ö(A1 + A2)

               A1 = Lx B = 10 x 8 = 80 m²

                 A2 = L1xB1= 6 x 4 = 24 m²     

                   =  2/3x(80+24+Ö(80+24))    

                   =   76.13 cum

The Volume of Hard rock = The volume of stacked quantity – Deduction for voids.

          Deduction for Voids should be pre-accepted and normally stated in the percentage of a stacked quantity. From the total quantity of the mixture the quantity of hard rock excavated thus arrived at shall be deducted to work out the quantity of the soft, disintegrated rock excavated.