List of top Soil Mechanics and Foundation Engineering Questions on Earth Pressure

Which of the following statements is/are INCORRECT?
 

A vertical trench is excavated in a clayey soil deposit having a surcharge load of 30 kPa. A fluid of unit weight 12 kN/m$^3$ is poured in the trench to prevent collapse as the excavation proceeds. Assume that the fluid is not seeping through the soil deposit. If the undrained cohesion of the clay deposit is 20 kPa and saturated unit weight is 18 kN/m$^3$, what is the maximum depth of unsupported excavation (in meters, rounded off to two decimal places)?

The figure shows a vertical retaining wall with backfill consisting of cohesive-frictional soil and a failure plane developed due to passive earth pressure. The forces acting on the failure wedge are: \(P\) as the reaction force between the wall and the soil, \(R\) as the reaction force on the failure plane, \(C\) as the cohesive force along the failure plane and \(W\) as the weight of the failure wedge. Assuming that there is no adhesion between the wall and the wedge, identify the most appropriate force polygon for the wedge. 

The figure shows a vertical retaining wall with backfill consisting of cohesive-frictional soil and a failure plane developed due to passive earth pressure. The forces acting on the failure wedge are: \(P\) as the reaction force between the wall and the soil, \(R\) as the reaction force on the failure plane, \(C\) as the cohesive force along the failure plane and \(W\) as the weight of the failure wedge. Assuming that there is no adhesion between the wall and the wedge, identify the most appropriate force polygon for the wedge. \includegraphics[width=0.75\linewidth]{image22.png}