The plastic limit of a soil is 20% and its liquid limit is 50%. If its flow index is 30%, find the value of the toughness index of the soil.

A rigid retaining wall 5 m high is restrained from yielding. The backfill consists of cohesionless soil having φ' = 30° and unit weight of soil γ = 18 kN/m3. Compute the total earth pressure per metre length of the wall at rest. (Consider sin(30°) = 0.5, cos(30°) = 0.866)

Calculate the average contact pressure (in kN/m2) directly beneath a square footing of dimensions 4 m × 4 m carrying a vertical load of 200 kN.