In this formula, the mean depth is to be calculated. First by avergaing the depths of two consecutive sections. From the mean-depth the area of mid-section is to be worked out and volume of arthwork to be compted by multiplying the area of mid-secion by the distance between the two original sections.

Volume of earthwork = ${A_m} * D$

where, ${A_m}$=area of mid-section

D=distance between two consecutive sections

To calculated ${A_m}$, calculate first ${d_m}$

${A_m}=B{d_m} + Sd_m^2$

$V= (Bd_m + Sd_m^2) * D$