Practice Question: Soil Effective stresses

Answer: A) 1723 PSF

Effective stress = Total stress – Pore water pressure

\[\sigma'_v= \gamma _1 h_1+ \gamma '_2 h_2+( \gamma _3 'h_3)/2\]

\[=80 \times 8+(120-62.4) \times 10+(130-62.4) \times15/2=1723\ PSF\]

Alternatively, it can be calculated as:

\[\sigma_v-U= \gamma _1 h_1+ \gamma _2 h_2+( \gamma _3 h_3)/2- \gamma _w (h_2+h_3/2)\]