Test: Earthwork Estimation - Civil Engineering (CE) MCQ

Irrigation helps grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of inadequate rainfall. Irrigation also has other uses in crop production, including frost protection, suppressing weed growth in grain fields and preventing soil. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dry land farming.

Volume of Sloped earthwork (V) = (bd_m + sd_m²) × L   
Where, B   = Width, d_m  = Mean depth and S = Side slope of the cross-section
Calculation:-
Volume of earthwork = 40.10 × 1.10 × 1 = 44.11 cum

In surface (furrow, flood, or level basin) irrigation systems, water moves across the surface of an agricultural lands, in an order to wet it and infiltrate into the soil. Surface irrigation can be subdivided into furrow, borderstrip or basin irrigation. It is often called flood irrigation when the irrigation results in flooding or near flooding of the cultivated land.

'Lift' is the vertical distance calculated from the ground level up to which the labourers have to excavate the soil and remove it for the standard rate. 

• It is the general practice or thumb rule to consider lift as 1.5 m.
• In case of more depth, the lift will be more, and hence the rate of removing it will be more.

Additional Information

• Lead: it is the horizontal distance up to which the excavated earth will be carried or transported on the ground from the source to the place of spreading.
• The general lead considered is 50 m for a distance up to 500 m and shall be measured separately. It means that it is measured for a distance per 50 m.
• If it exceeds further then a separate rate is applied.

A table for lead distance is provided for a better understanding

It is a system where water is distributed under low pressure through a piped network, in a pre-determined pattern, and applied as a small discharge to each plant or adjacent to it. Traditional drip irrigation using individual emitters, subsurface drip irrigation (SDI), micro-spray or micro-sprinkler irrigation, and mini-bubbler irrigation all belong to this category of irrigation methods.

Volume of Sloped earthwork (V) = (bd + sd²) × L   
Where, B   = Width, d  = Depth and S = Side slope of the cross-section
Calculation:
Given,
slope = s: 1 = 3: 1
b = 10 m
L = 120 m
d₁ = 1.5 m and d₂ = 1 m
Volume of Sloped earthwork (V) = (bd + sd₂) × L

The approximate quantity of earthwork = 2085 m³

This method can be the most water-efficient method of irrigation, if managed properly, evaporation and runoff are minimized. The field water efficiency of drip irrigation is typically in the range of 80 to 90 percent when managed correctly.

The earthwork means the excavation of soil from the earth to be done in order to make the desired size of the beam. The amount of earthwork is measured in either square meter m² or cubic meter or m³ units depending on the following conditions:

• Earthwork is measured in m² if surface excavation does not exceed 30 cm in depth but exceeds 1.5 m in width as well as 10 sqm.
• In all other cases, it is measured in cum.

Calculation:
Given that for a plinth: Length = 4.3 m; Breadth = 2 m and Height = 0.5 m

• Depth = 0.5 m i.e. exceeding 30 cm è  it can not be measured in sqm
• Width = 2 m i.e. exceeding the 1.5 m
• Plan area = 4.3 × 2 = 8.6 m² not exceeding from 10 sqm → it cannot be measured in sqm

Based on the above, it can be concluded that earthwork is to be measured in m³ and it is determined as:
Earthwork = Length × Width × Height
Substituting these values above, we get
Earthwork = 4.3 × 2 × 0.5 = 4.3 m³

The two terms are sometimes used interchangeably however chemigation is generally a more controlled and regulated process due to the nature of the chemicals used. Chemigation often involves pesticides, herbicides, and fungicides, some of which pose health threat to humans, animals, and the environment.

Mid-Sectional Area Method

• The mean depth is the average of depths of two consecutive sections
• The area of mid-sections is calculated by using mean depth
• The volume of the earthwork is calculated by multiplying the mid-section area by the distance between the two sections

The formula used for finding the amount of earthwork using the mid-sectional method is given by:
Q = A x L 
where,
Q = Volume of earthwork
A = Area of mid-section = BD_m + SD_m² 
B = Width of road
D_m = Depth at mid-section = 
S = Slope
L = Length of road
Hence, Q= (BD_m + SD_m²)L
Calculation:
Given data:
D₁ = 1 m
D₂ = 1.6 m
L = 200 m
B = 10 m
S = 2

Now, 
A = (10 x 1.3) + (2 x 1.3²) = 16.38 m²
Now, 
V = 16.38 x 200 = 3276 m³