Answer Happy

A slope cut to 1.5H:1V will be made in a shale rock stratum (unit weight y=20.1kN/m3) that has bedding planes with an apparent dip of 16º. Check the slope stability of this construction for the following three scenarios (assume the acceptance factor of safety is 2.5): a) when the water table is far below the structure. Use the bedding plane strength parameters of c=22kN/m2 and O=30° [6 marks] b) when the water table (phreatic surface) is given as in the figure (the maximum distance between the slip plane and the phreatic surface is 3.2 m and the average is 2 m) and the strength parameters are the same. [6 marks] c) when the water table (phreatic surface) is given as in the figure (the maximum distance between the slip plane and the phreatic surface is 3.2 m and the average is 2 m) but the strength parameters are reduced as c'=15kN/m2 and O'=20°. [6 marks] d) Explain the effect of the water table based on your answers of the above questions. [6 marks] 85.0 m Original ground surface 7 13.2 m 1.5 11.3 m 20.0 m Seepage Rock's bedding planes 16° Proposed new ground surferce