GATE 2016 CE (CE1) – Question 53
A seepage flow condition is shown in the figure. The saturated unit weight of the soil γsat = 18 kN/m3. Using unit weight of water, γw = 9.81 kN/m3, the effective vertical stress (expressed in kN/m2) on plane X-X is ________
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Correct answer: 65.3 to 65.6
Explanation
The total head drop is3m over6m of soil, giving downward hydraulic gradient0.5. At depth5m, total stress is18·5+9.81·4=129.24kPa. Pressure head is4+5−0.5·5=6.5m, so u=63.765kPa. Effective stress is129.24−63.765=**65.475kPa**; downward seepage increases it relative to hydrostatic conditions.