Rate Analysis of Excavation in Earthwork -Calculate Cost of Excavation
Gopal Mishra
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Rate analysis of excavation in earthwork is the measure of quantity of excavation to be carried out, the cost of equipment, machineries and labors required for the same.
The cost of excavation depends on the depth of excavation, type of soil, method of excavation to be carried out and the distance where the excavated soil has to be disposed. The cost of all these are added for unit volume of excavation to get the rate of excavation.
The cost of excavation based on depth is generally divided into categories as:
For depth upto 1.5m
For depth between 1.5m to 3m.
For depth between 3.m to 4.5m.
For depth more than 4.5m
The depth of excavation required varies from project to project and from place to place. Many factors influence the depth of excavation. We will not go into the details about the same.
Summarizing above points, it can be seen that the rate analysis for excavation work can be divided by following ways:
The first method is the selection of type of soil to be excavated and lead distance where the soil has to be disposed off. Then the other variable that is considered is the depth of excavation and is presented in the rate analysis description as follows:
1. Excavation in earthwork for soft soil for a lead distance of 1km for following depths:
a) Up to 1.5m
b) 1.5m to 3m
c) 3m to 4.5m
2. Excavation in earthwork for hard soil/ hard rock for a lead distance of 1km for following depths:
a) Up to 1.5m
b) 1.5m to 3m
c) 3m to 4.5m
In the above examples of excavation, more number of descriptions are possible with different lead distance and type of soil. During tendering of civil engineering works, all the possible combinations are presented for quotations depending on the project requirements and site conditions.
Rate Analysis of Excavation:
Following points to be noted before starting rate analysis of soil:
Type of soil
Lead distance and transport for carrying excavated soil
Depth of excavation
Method of excavation - manual excavation or mechanical excavation
Capacity of labor for manual excavation
Capacity of equipment for mechanical excavation and their cost per unit quantity.
Water charges if used
Profit of contractor
We will see an example of excavation of soft soil for a depth up to 1.5m and lead distance of 50m per 10m3 of concrete.
Items
Units
Qty.
Rate
Amount
Hydraulic Excavator
Day
0.04125
5000
206.25
Tractor/Dumper
Day
0.04125
1500
61.88
Unskilled Labor
Day
1.20
311.2
373.44
Total
641.57
Water charges @1% total
6.42
Contactor Profit @15%
96.23
SUM
744.22
Gross Amt./CUM up to 1.5m depth
COST
74.42
In the above example, the coefficient of quantity of hydraulic excavator, tractor / dumper and unskilled labors are based on their capacity per day (8 hours of work). Lets say for 10m3, the hydraulic excavator is taking 0.04125 day. Then its capacity considered is ((1x10)/0.04125) = 242.4242 m3 / day.
That means, a hydraulic excavator can excavate 242.4242 m3 of soil in one day. Its cost per day including driver and fuel is Rs. 5000. Then the cost of 10m3 of excavation can be calculated as:
No. of days required for 10m3 excavation = 10/242.4242 = 0.04125 days.
The cost of hydraulic excavator for 10m3 excavation = 0.04125x5000 = Rs.206.25
Likewise, based on the capacity of other equipment, labors etc., their cost is calculated. Contractors profit is also added to the total cost of labors and machineries. Then grand total gives the rate of excavation per 10m3 of soil excavation.
Different mechanical equipment have different capacity per day for excavation work. Their coefficient per m3 or per 10m3 should be considered for calculation.
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