construction site earthwork calculation

8/13/2019 Construction Site Earthwork Calculation

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With advancement of Technology there is a lot of progress in the way we take Ground reading. Earlier

only Auto Levels were used, whereas now Total Station, GPS, LIDAR are being used to take ground

reading. Previously Earthwork Calculations were simply done on paper followed by some simple

computer applications. Now, however, either Spread Sheets likes Excel are used or advanced software

products which are specifically designed for earthwork calculation are used. But volumetric calculations

done by software still have to presented in understandable manner even while getting different results

from different software products.

There are three different methods popularly used for doing Earthwork Calculation for Cutting/FillingProjects. Before discussing these in detail let us try to understand Some Basic definition of Terms

related to Earthwork Calculation.

Earthworks

Earthworks are engineering works created through the moving and/or process ing of massive quantities

of soil or unformed rock. Earthwork is done to reconfigure the topography of a site to achieve the

design levels. Earthwork involves cutting and filling to achieve the required topography.

Cutting

Cutting is the process of excavating earth material from a work location to achieve the desiredtopography.

Filling

Filling is the process of moving the excavated material or additional earth material to a work location to

achieve the desired topography.

Let us take 2 Simple Examples for our Study

In the Example below the plot is 30 X 30 Meters and all the Grid levels measured at Grid level of

10M

Example 1 (Only Cutting)

Ground Level

Section 0 10 20 30

30192.51193.71193.21193.47

20193.04193.14192.92193.01

10192.61192.56192.63192.67

0192.56192.68192.67192.57

Formation Level

191.9 193.1 192.6192.87192.43192.53192.31 192.4

192.01191.96192.03192.06

191.95192.07192.07191.97

Example 2 (Both Cutting andFilling)

Ground Level

192.51 193.71 193.21 193.47

193.04 193.14 192.92 193.01

192.61 192.56 192.63 192.67

192.56 192.68 192.67 192.57

Formation Level

193.4 193.5 193.3 193.2193.5 193.3 193.2 193.4

193.4 193.6 193.4 193.4

193.1 193.4 193.5 193.3

Average method:

In this method Levels at each grid point is found out. Difference between the Average of Two Sets of

Levels multiplied by Area gives the Result. This is a very simple and straight forward method. But this

can be used only when there is cutting or filling. When Leveling of surface includes both cutting and

filling, Average method gives wrong result as cutting and filling values nullify each other whileaveraging.

Example 1(Only Cutting)

Filling

Example 2 (Both Cutting andFilling)


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0 0 0 0

0 0 0 0

0 0 0 0

0 0 0 0

Average 0 0

Cutting

0.61 0.61 0.61 0.60.61 0.61 0.61 0.61

0.6 0.6 0.6 0.61

0.61 0.61 0.6 0.6

Average 0.606 545.62

Filling

00.21 0 0.27

0 0 0 0

0 0 0 0

0 0 0 0

Average 0.03 27

Cutting

0.89 0 0.09 00.460.16 0.28 0.39

0.791.04 0.77 0.73

0.540.72 0.83 0.73

Average0.526 473.625

Volume = Average * 900 = 0.606 * 900 = 545.62

Block Method (Division of Square Method):

In this method, volume of cutting or filling is found out for each block and added together to get thefinal volume. This is mathematically simpler then Section Method, but more accurate than Average

method. The problem of nullification is also encountered here when in the same block there is both

cutting and filling. But here the margin of error is very small when compared to Average method for

whole area.

Example 1(Only Cutting):

Difference in Average for Each 10 X 10 Block

0.61 0.61 0.6075

0.605 0.605 0.6075

0.605 0.6025 0.6025

Volume = Sum * 100 (Area of Each block) = 5.455 * 100 = 545.5 (Cutting)

Note: Value 0.61 = Average (192.51, 193.71, 193.04, 193.14) Average (191.9, 193.1, 192.43, 192.53)

[Values taken from first 2 rows and 2 columns of ground and formation level)

Example 2 (Both Cutting and Filling) :

Difference in Average for Each 10 X 10 Block

0.325 0.08 0.1225

0.6125 0.5625 0.54250.7725 0.84 0.765

Volume = Sum * 100 (Area of Each block) = 4.6225 * 100 = 462.25 (Filling).

Note: Although in this example there is some cutting, because of nullification of value in same block we

are not getting any value in Cutting.

Section Method:

In this method Sections are drawn for Each Line of Value. Area of Cutting and Filling is found out for

each Section w ith Trapezoidal Method or Nett Area Calculation Method. Then volume is de termined bymultiplying Average Area w ith Distance between Sections. This method is more accurate, but for larger

area, finding the area becomes difficult as we need to find intersection of points where lines

representing Surfaces meet.


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Example 1(Only Cutting):

Sl.

No.Section

Cutting Volume Filling Volume

Area

Sq. Mtrs

Previous

Area

Average

Sq. Mtrs

Volume

Cu Meters

Area

Sq. Mtrs

Previous

Area

Average

Sq. Mtrs

Volume

Cu Meters

1 0.000 18.150 0.000 9.075 0.000 0.000 0.000 0.000 0.000

2 10.000 18.050 18.150 18.100 181.000 0.000 0.000 0.000 0.000

3 20.000 18.300 18.050 18.175 181.750 0.000 0.000 0.000 0.000

4 30.000 18.250 18.300 18.275 182.750 0.000 0.000 0.000 0.000

Total 545.500 0.000

Sections Related to Example 2 (Both Cutting and Filling) :

Example 2 (Both Cutting and Filling) :

Sl.

No.Section

Cutting Volume Filling Volume

Area

Sq. Mtrs

Previous

Area

Average

Sq. Mtrs

Volume

Cu Meters

Area

Sq. Mtrs

Previous

Area

Average

Sq. Mtrs

Volume

Cu Meters

1 0.000 0.000 0.000 0.000 0.000 21.850 0.000 10.925 0.000

2 10.000 0.000 0.000 0.000 0.000 25.700 21.850 23.775 237.750

3 20.000 0.000 0.000 0.000 0.000 8.650 25.700 17.175 171.750

4 30.000 1.948 0.000 0.974 9.740 3.848 8.650 6.249 62.490

Total 9.740 471.990

Summary of Results

Sl. Method Example 1 Example 2

Cutting Filling Cutting Filling

1 Average Method 545.62 0 27.000 473.625

2 Block method 545.5 0 0.000 462.25

3 Section Method 545.500 0 9.740 471.990

Summary of Various Methods

Methods /


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Methods Formula Advantages Disadvantages Applicability

Average

Method

Volume=Depth of

cutting/filling*

area

Easiest Method for

calculation

Approximate,

cannot be

applied when

both cutting

and filling are

there

Used for very small

projects

Block

Method

Volume=Sum of(Depth o f

cutting/filling*

area of each

block)

It Is very easy to

calculate the area

Box method willnullify volume when

both cutting and

filling are there in

the same block

Commonly used to

find volume for

leveling projects

before the

construction of a

building

Section

Method

Area to be found

out using

Trapezoidal

Method

Nett area

Method

Volume =

Lx1/2(A1+ A2)

Mathematically,

very good and

hence adopted in

majority of

infrastructureprojects

Involves a lot of

calculations

Used in most of the

infrastructure

Projects including

Roads, Irrigation

Projects, Rail RoadProjects, etc.

Conclusion

From the above examples, we can conclude that Section Method is complex compared to any other

method but gives accurate results. Also if the Average method or Block Method is used for calculation

then it is likely that Volume w ill be little lesser and the contractor will get lesser quantity and hence less

payment for his work.

construction site earthwork calculation

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