Answer the latter part first:150 *15.8 *15.8 * 0.015 = road length * road width (15+0.4*2 working face width) * [road width * road cross slope] Among them, 15.8 is understood as an increase of 0.4m on both sides of the working face width.

The whole formula is not clear, and I feel lack of boundary conditions:

1, the transverse slope of soil subgrade that needs to be reshaped after excavation is generally+0.1%;

2. What is the excavation slope on both sides of the roadway? Generally1:1.5;

3. Does the average digging depth mean the digging depth at the center line of the road?

If the above boundary conditions are determined, then the calculation of earthwork is a mathematical problem!

What to say? I don't know if I understand it. Does it help?