GATE Civil Engineering (CE) 2018 Shift 1 Solved Paper

Question : 13 of 65

Marks: +1, -0

The percent reduction in the bearing capacity of a strip footing resting on sand under flooding condition (water level at the base of the footing) when compared to the situation where the water level is at a depth much greater than the width of footing, is approximately

Validate

Solution:

q_{u}=C ⋅ N_{c}+(γ ⋅ D_{e}) ⋅ N_{q}+\;{1}/{2} B γ N_{γ}

(Strip footing) for footing on sandy ground,

{C}=0 ; {D}_{ {f}}=0

⇒ {q}_{u}=\;{1}/{2} {B} γ {N}_{7}

(when water table is at a depth greater than width (B)of footing)
When water table comes at ground level than

γ=γ^{'}

{q}_{ {u}}=\;{1}/{2} {B} γ^{'} {N}_{7}

∴ γ^{'}=\;{γ}/{2} ⇒ {q}_{ {u}}=\;{1}/{4} {B} γ {N}

⇒ \%

reduction in

q_{u}=\;{\;{1}/{2} B y N_{7}-{1}/{4} B y N_{y}}/{{1}/{2} B y N_{7}} × 100 \%=50 \%

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