Question

Calculate the height of water table rise in soil mass from a sand stratum of 12m deep from ground level, at which the effective pressure is zero. The water percolates through a soil mass of thickness 5m. The γsat=18.6 kN/m^3 and γw=9.81 kN/m^3.

(a) 7.68m

(b) 9.48m

(c) 5.24m

(d) 10m

The question was posed to me during an interview.

The doubt is from Seepage Pressure and Upward Flow topic in portion Seepage Analysis of Geotechnical Engineering I

Answer 1

Correct answer is (b) 9.48m

For explanation I would say: Given,

Thickness of soil mass=12m

water percolates through a soil mass of thickness 5m

γsat=18.6 kN/m^3

 γw=9.81 kN/m^3

the effective pressure at sand stratum becomes aero,

σ’=zγsat-hwγw

∴hw= zγsat/γw

hw=5*18.6/9.81=9.48m.