To have zero active pressure intensity at the top of a wall in cohesive soil, one should apply a uniform surcharge intensity of

2c tan

α

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2c cot

α

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-2c tan

α

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-2c cot

α

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Solution

The correct option is A 2c tan $α$

Active earth pressure

$P_{a} = K_{a} σ_{a} - 2 c \sqrt{K_{a}}$

$P_{a} = K_{a} (q + γ z) - 2 c \sqrt{K_{a}}$

$G i v e n, a t z = 0, P_{a} = 0$

$0 = K_{a} q - 2 c \sqrt{K_{a}}$

$q = \frac{2 c}{\sqrt{K_{a}}}$

$= \frac{2 c}{\sqrt{\frac{1}{t a n^{2} (45 + \frac{ϕ}{2})}}}$

$= 2 c t a n (45 + \frac{ϕ}{2})$

$= 2 c t a n α$

Note:

$α = Angle of failure plane with major principal plane$

$α = 45 + \frac{ϕ}{2}$

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Similar questions

Q. A 6 m high retaining wall with a surcharge of

5 k N / m^{2}

at the ground surface shown in the figure

The Rankine active pressure (in kN/m) on the wall before the formation of cracks is ?

Q. Consider a rigid retaining wall with partially submerged cohesionless backfill with a surcharge. Which one of the following diagrams closely represents the Rankine's active earth pressure distribution against this wall?

Q. Assertion (A): The safe height

(2 z_{0})

to which an unsupported vertical cut in clay be made is

4 c / γ .

Reason (R): Active earth pressure of cohesive backfill shows that the negative pressure (tension) is developed at top level. This tension decrease to zero at depth

z_{0}

and total net pressure up to a depth

2 z_{0}

is zero.

Q. Consider the following statements:
1. In the case of footings on purely cohesive soils, the benefit due to surcharge or depth of foundation is only marginal.
2. The bearing capacity of a footing in pure clay may be increased by increasing its size.
3. Factor of safety should be applied only to the net ultimate bearing capacity.
which of the above statements are correct ?

The intensity of passive earth pressure at a depth of 5 m in a cohesion less soil with an angle of internal friction of $30^{\circ}$ when water rises to ground level is $k N / m^{2}$ . Take saturated unit weight of sand as $21 k N / m^{3}$ and $γ_{w} = 9.81 k N / m^{3}$ .

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To have zero active pressure intensity at the top of a wall in cohesive soil, one should apply a uniform surcharge intensity of

The correct option is A 2c tan α Active earth pressure Pa=Kaσa−2c√Ka Pa=Ka(q+γz)−2c√Ka Given, at z=0, Pa=0 0=Kaq−2c√Ka q=2c√Ka =2c  ⎷1tan2(45+ϕ2) =2c tan(45+ϕ2) =2 c tanα Note: α= Angle of failure plane with major principal plane α=45+ϕ2