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Steady state seepage is taking place through a soil element at Q, 2 m below the ground surface immediately downstream of the toe of an earthen dam as shown in the sketch. The water level in a piezometer installed at P, 500 mm above Q is at the ground surface. The water level in a piezometer installed at R, 500 mm below Q, is 100 mm above the ground, surface. The bulk saturated unit weight of the soil is 18 kN/ m3 and the unit weight of water is 9.81 kN/m3. The vertical effective stress (in kPa) at Q is.
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- 14.42
- 15.89
- 16.38
- 18.34
Correct Option: B
Pore water pressure, µ = γw. h.
µP = γw × 1.5 m
µR = γw × (2.5 + 0.1) = γw × 2.6
µ varies linearly with depth. As P & R are at equal distance from θ, µQ will be average of UP and UR.
Effective stress, σ = σ – U
at Q = γsat. h – UQ.
= 18 × 2 – 2.05 × 9.81 = 15. 89 kPa
