## Exercise

A 6 m high retaining wall with a smooth vertical back retains a mass of dry cohesionless soil that has a horizontal surface level with the top of the wall and carries a uniformly distributed load of 10kN/m2. The soil weighs 20kN/m3 and has an angle of internal friction of 36°.

Determine the active thrust on the back of the wall per metre length of wall (i) without the uniform surcharge and (ii) with the surcharge.

The back of a 10.7 m high wall slopes away from the soil it retains at an angle of 10° to the vertical. The surface of the soil slopes up from the top of the wall at a surcharge angle of 20°. The soil is cohesionless with a density of 17.6 kN/m3 and <j>' = 33°.

If the angle of wall friction, 8', = 19° determine the maximum thrust on the wall: (a) graphically and (b) analytically using the Coulomb theory.

A 4 m high wall retains two horizontal layers of saturated soil, both 2 m thick. The upper soil has a unit weight of 18 kN/m3, </> = 30° and c' = 0. The lower soil has a unit weight of 24kN/m3, 0' = 40° and c' = 0. For both soils the angle of wall friction, 8', may be assumed to be equal to 12.5°. Using the Coulomb theory determine:

(i) the horizontal and vertical components of the total active thrust acting on the back of the wall;

(ii) the total horizontal thrust that will act on the back of the wall if a standing water level develops behind the wall at an elevation of 1.0 m above its base.

(ii) Total horizontal thrust = 38.5 kN

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