Road Estimation Approaches

Road Estimation Approaches

For the calculation of earthwork in roads longitudinal section and cross-section of the ground are taken and the formation line is fixed. The formation line is fixed in consideration of floods, gradient, height of bank, depth of cutting, etc. in plain countries road is usually in banking, but if the road is cutting for some length and in banking for some other length, the excavated earth from the cutting portion should be utilized for the banking portion with in economical limits, during the execution of work. Earthwork is general term used for both cutting and banking (filling).

Sub Grade:-
As the surface of earth covered in road construction is usually not of same reduced levels therefore a layer of earthwork is done over it is termed as sub-grade.

Volume Calculation of the road bank:-
Usually banks of roads are of trapezoidal shape and calculations for its volume are made for some specific unit length usually 30ft (normal tape length).

There are three approaches to calculate the volume

Mid Sectional area Method:-

Area = A = Bd_m + Sd²_m
Volume = A × L

Mean sectional Area method:-

A₁ = Bd₁ + Sd²₁
 A₂ = Bd₂ + Sd²₂
 A_m = ( A₁ + A₂  ) / 2
V = A_m × L

Prismoidal Formula Method:-

Q.1 Calculate the quantity of earthwork for two hundred meters of length for portion of road in a uniform ground. The height of bank at two ends being 1m & 1.6m. Formation width is 10m & side slope are 2:1 (H:V).

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