GATE Civil Engineering (CE) 2020 Shift 1 Solved Paper

Question : 44 of 65

Marks: +1, -0

The soil profile at a site up to a depth of

10 {m}

is shown in the figure (not drawn to the scale). The soil is preloaded with a uniform surcharge (q) of

70 {kN} \/ {m}^{2}

at the ground level. The water table is at a depth of

3 {m}

below ground level. The soil unit weight of the respective layers is shown in the figure. Consider unit weight of water as

9.81 {kN} {/} {m}^{3}

and assume that the surcharge (q) is applied instantaneously.

Immediately after preloading, the effective stresses (in kPa) at points P and Q. respectively, are

Solution:

Surcharge is applied instantaneous

∴

Extra pore water pressure of

7 {kPa}

is develated.

\ov{σ_{ {p}}}=σ_{ {p}}- {v}_{ {p}}

σ_{p}=70+18 × 3=124

u_{p}=0+70=70

\ov{σ_{ {p}}}=124-70=54

\ov{σ_{q}}=σ_{q}-v_{q}

σ_{q}=70+18 × 3+20 × 4=204

v_{q}=9.81 × 4+70=109.24

\ov{σ_{p}}=204-109.24=94.76 {kPa}

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