(c) A clay layer of 10 m thick with an average bulk unit weight y = 18.5 kN/m³ overlies a sand aquifer. It was observed to begin an excavation base failure due to artesian water pressure at an excavation depth of 6 m into this clay layer. If a piezometer is installed into the sand aquifer determine the depth to the water level in the piezometer from the surface.

It is known that a particular deposit of clay has the following shear strength parameters: c' = 15 kPa, o' = 23°; Cu = 10 kPa, cu = 13° A sample of this clay is consolidated in a triaxial cell to an all-round pressure (03) of 250 kPa. The sample is then sheared by increasing 0₁, keeping 3 constant and the drainage valve closed. What is: i) ₁ at failure? ii) Pore water pressure inside the sample at failure? iii) Final values of 0₁' and 03'? iv) Value at failure of Skempton's pore pressure coefficient A?

The hydraulic head that would produce a quick sand condition in a sand stratum of thickness 1.8 m, specific gravity 2.65 and void ratio 0.65 is equal-to

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