NCEES Geo PM book question 520 - bearing capacity

[ketanco]

Hello,

In the NCEES Geotechnical afternoon sample questions, question 520, for the depth while calculating the D, why do they take 2 feet and not 10, which is (2+8) feet up to the overall ground surface?

for the ones that do not have, the question asks bearing capacity of a footing in the basement of a building. the footing is 2 feet below the basement ground level, but it is 10 feet below the overall ground level around the building. i calculated using 10 feet, but in the solution it calculates by taking 2 feet only and i dont know why.

Thanks

 

[icreep]

D = 2ft because that is the depth of the fill above the footing base. Above that is empty space. Use D = 10ft only if the entire void space is filled with soil.