Rate analysis for earth excavation establishes the rate of labor and equipment required to excavate a site. Unlike other rate analysis works, the rate analysis of earth excavation does not undertake any material analysis.
Manual or machine excavation method or the combination of both is used for earth excavation. The process of excavation depends on the type and complexity of excavation.
The article explains a general rate analysis of earthwork excavation performed manually as well as with the help of machines.
Contents:
- Features of Rate Analysis of Earthwork Excavation
- Rate Analysis of Manual Earthwork Excavation
- Step 1: Investigate Site and Determine the tasks
- Step 2: Determine the Volume of Excavation (m3)
- Step 2: Determine the Labour time Required for 1m3 Excavation
- Step 3: Determine the cost of Mate and Mazdoor for Excavation
- Step 3: Determine the Cost of Tools & Equipment for Manual Earth Excavation
- Step 4: Determine the Overhead Cost and Profit
- Rate Analysis of Machine-based Earthwork Excavation
- Frequently Asked Questions
Features of Rate Analysis of Earthwork Excavation
The cost of excavation depends on the depth of excavation, type of soil, method of excavation to be carried out, and the distance from which the excavated soil has to be disposed of. All the costs are added for a unit volume of excavation to get the rate of excavation.
The respective area codes of a region or a country follow a specific rate of labor productivity and a specific labor output constant.
For example, IS 7272 -1974 provides the labor output constants for building work for different country zones. It gives the coefficient value of days required by a particular type of labor to conduct a 1-meter cube volume of excavation.
Rate Analysis of Manual Earthwork Excavation
The concept can be explained with a simple example.
Consider a work where it is required to excavate a pit of following dimensions:
Breadth (b) = 2000; Length (l) = 4000mm and Depth (d) = 1000mm;
Steps involved in rate analysis are:
Step 1: Investigate Site and Determine the tasks
Determine the type of soil of the site and associated tasks to conduct safe excavation. Sometimes, the excavation may require shoring or dewatering. If there is hard strata beneath, there is a requirement for blasting. Also, check the provision for working space and safety features associated with this.
Listing out the tasks involved can help predetermine the labor and equipment required for the excavation.
Step 2: Determine the Volume of Excavation (m3)
As mentioned in the example, beyond the required dimension of the pit, a minimum working space of around 150mm around the pit is provided.
Let the final dimension of the pit be:
Breadth(b) = 2000mm; Length (b) = 4000mm and Depth(d) = 1000mm;
Volume of excavation (Vp) = Length x Breadth x Height
= [4000 x 2000 x 1000 ] in mm ~ [4 x 2 x 1] in metres ~ 8m3
Step 2: Determine the Labour time Required for 1m3 Excavation
As per IS 7272-1974, for North Zones of India,
From the figure,
The number of days required to perform 1m3 of excavation by a mate is 0.06, and that for a mazdoor is 0.62. (Assume the case of hard dense soil).
Hence, to perform ‘V’= 8m3 excavation:
Number of Mate = 0.06V = 0.06 x8= 0.48 nos
Number of Mazdoor = 0.62V=0.62 x 8 = 4.96 nos
This means approximately, 1 Mate and 5 numbers of Mazdoor are required to finish the excavation of the given depth in one day.
Step 3: Determine the cost of Mate and Mazdoor for Excavation
The cost of labor or machinery is obtained from Schedule of Rates (SOR) that can be taken based on PWD or Public sectors or trends of the market with respect to a particular region.
The rate of labor can be either scheduled as a rate per square feet or rate of unskilled labor per day.
Let the labor cost of mate be Rs. 370 per day, and labor cost for mazdoor be Rs. 280 per day. Then,
The cost of Mate = No. of mates x cost per mate =1 x 370= Rs. 370
The cost of Mazdoor= No. of mazdoor x cost per mazdoor= 5 x 280
= Rs. 1400
Total Cost of Labour
= The cost of mate + The cost of Mazdoor = 370 + 1400 = Rs.1770/-
Step 3: Determine the Cost of Tools & Equipment for Manual Earth Excavation
The cost of tools and equipment can be taken as a percentage of labor costs. (Assuming 5% of labor cost as the cost of tools and equipment)
Cost of tools and equipment for 8m3 Earth Excavation
= 5% x (1770) = 0.05 x 1770= Rs. 88.5
The Basic Cost of Excavation for 8m3 Earth Excavation
= Labour Cost + Cost of Equipment = 1770 + 88.5 = Rs. 1858.5
Step 4: Determine the Overhead Cost and Profit
The overhead cost and profit = 20% of Basic cost of excavation
= 0.20 x 1858.5 = Rs. 371.7
Therefore,
Total Cost Including OH and Profit= 1858.5+ 371.7= Rs. 2230.2
Rate Analysis of Machine-based Earthwork Excavation
Consider an example of excavation of soft soil for a depth of up to 1.5m and lead distance of 50m per 10m3 of concrete. Here, the coefficient of quantity of hydraulic excavator, tractor/dumper, and unskilled labors is based on their capacity per day (8 hours of work).
| 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 | |||
| Contractor Profit @15% | 96.23 | |||
| SUM | 744.22 | |||
| Gross Amt./CUM up to 1.5m depth | COST | 74.42 |
Capacity of the Equipment
From the table above, the hydraulic excavator takes 0.04125 day to perform an excavation of 10m3. It takes 0.04125 days to perform a 10m3 excavation. Then in 1 day, it performs :
(1 x [ 10/0.04125]) m3 of excavation = 242.24m3/day
This is actually the capacity of the hydraulic excavator.
That means- a hydraulic excavator can excavate 242.4242 m3 of soil in one day.
Cost of Equipment
From table-2, the cost per day, including driver and fuel for a hydraulic excavator 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, laborers, etc., their cost is calculated. Contractor's profit is also added to the total cost of laborers and machineries. Then the 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.
Frequently Asked Questions
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 of. The cost of all these is added for a unit volume of excavation to get the excavation rate.
The respective area codes of a region or a country follows a specific rate of labor productivity and a specific labor output constant.
For example, IS 7272 -1974 provides the labor output constants for building work for different zones of the country. It gives the coefficient value of days required by a particular type of labor to conduct a 1-meter cube volume of excavation.
Rate analysis of earth excavation establishes the rate of labor and equipment required to excavate the site. Unlike other rate analysis works, the rate of earth excavation does not undertake any material analysis.
Manual or machine excavation method or combination of both are used for earth excavation. The process of excavation depends on the type and complexity of excavation.
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