A retaining wall of height 10 m with clay backfill is shown in the fig...
° and the clay backfill has a cohesion of 30 kPa and an angle of internal friction of 25°.
To calculate the factor of safety against sliding, we need to determine the total driving force (resisting force) and the total resisting force (driving force).
Total driving force = weight of retaining wall + weight of backfill
Weight of retaining wall = 5000 kN/m x 10 m = 50,000 kN
Weight of backfill = volume of backfill x unit weight of backfill
Volume of backfill = (10 m + 4 m) x (15 m + 4 m) x 10 m = 1,900 m^3
Unit weight of backfill = 20 kN/m^3 (assuming saturated clay)
Weight of backfill = 1,900 m^3 x 20 kN/m^3 = 38,000 kN
Total driving force = 50,000 kN + 38,000 kN = 88,000 kN
Total resisting force = frictional force + cohesive force
Frictional force = normal force x coefficient of friction
Normal force = weight of retaining wall + weight of backfill
Coefficient of friction = tan(20°) = 0.364
Frictional force = (50,000 kN + 38,000 kN) x 0.364 = 29,480 kN
Cohesive force = cohesion x length of retaining wall
Length of retaining wall = 15 m + 4 m = 19 m
Cohesive force = 30 kPa x 19 m = 570 kN
Total resisting force = 29,480 kN + 570 kN = 30,050 kN
Factor of safety against sliding = total resisting force / total driving force
Factor of safety against sliding = 30,050 kN / 88,000 kN = 0.342
The factor of safety against sliding is less than 1, indicating that the retaining wall is not stable against sliding. To increase the factor of safety, options include increasing the frictional force by increasing the interface friction angle or using a rougher base material, or increasing the cohesive force by using a backfill material with a higher cohesion. Alternatively, a geosynthetic reinforcement or soil nails could be added to increase the resistance to sliding.
A retaining wall of height 10 m with clay backfill is shown in the fig...

The factor of safety (round off to two decimal places) against sliding failure of the retaining wall after ignoring the passive earth pressure will be _______.

Z
c = 3.488
f = μN = (tan δ) W

