Consider the seepage beneath a retaining wall shown in Figure 1 below. The foundation rock around the wall is homogeneous and isotropic with a hydraulic conductivity of 1 x10 m/s.

It extends to an impermeable rock, DEF. The surface of the foundation rock is shown with dashed lines (AD and CF). On the right of CF is crushed gravel which,because of its high permeability, can be treated like a layer of water;, there is no need to consider seepage through it. Above surface AD is a 0.5m deep layer of surface water. The water level in the gravel is at the surface of the gravel layer. For simplicity, take gravitational acceleration to be 10m/s and water density to be 1000kg/m'. a) A larger version of Fig. 1 is provided on supplementary sheet #1 at the end of this examquestion. Construct a quantitatively accurate flow net, with nmsure to attach the sheet to your exam script prior to submission. Indicate numerical valuesfor each equipotential line and the direction of flow.3.5 flow tubes, on it. Be b) Calculate the exit velocity along the exit face (CF). c) Do you anticipate piping? Justify your answer in one or two sentences.[2 d) Calculate the force along AB đue to seepage through the soil.