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Foundation Engineering

Active Pressure -V

The soil prof...

Question

The soil profile at a site consists of a 5 m thick sand and layer underlain by a $c - ϕ$ soil as shown in figure. The water table is found 1m below the ground level. The entire soil mass is retained by a concrete retaining wall and is in the active state. The back of the wall is smooth and vertical. The total active earth pressure (expressed in $k N / m^{2}$ ) at a point A as per Rankine's theory is .

69.654

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Solution

The correct option is A 69.654
$K_{a_{2}} = \frac{1 - s i n 24^{\circ}}{1 + s i n 24^{\circ}} = 0.4217$

${¯ ¯ ¯ σ}_{A} = 16.5 + 4 (19 - 9.81) + 3 (18.5 - 9.81) = 79.33$

$σ_{a} = K_{a_{2}} {¯ ¯ ¯ σ}_{A} + γ_{w} \times 7 - 2 \times 25 \sqrt{K_{a_{2}}}$

$= 0.4217 \times 79.33 + 7 \times 9.81 - 50 \sqrt{0.4217}$

$σ_{a} = 69.654$

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