Answer Happy

6 m 20 m *1.5m 1 E 10 m G 1 1 e=0.85 G = 2.67 Ik= 3 x 10-3 cm/s Impervious clay FIGURE Q1 (C)
c) A dam shown in Figure Q1 (c) retains 6m of water. A sheet pile wall on the upstream side (which is to reduce seepage under the dam) penetrates 4m into a 10m thick of silty sand stratum. Below the silty sand is a thick deposit of clay. Assume that the silty sand is homogeneous and isotropic. (i) Calculate q in cm/s. (2 marks) (ii) Analyze the pore water pressure distribution on the front of the sheet pile (at every 2m @ at points A, F and G). Given the Na of points A, F and G are 0.5, 1.5 and 3.0 respectively. (3 marks) (iii) Analyze the pore water pressure distribution at the base of the dam. (at every 5m @ at points A, B, C, D and E). Given the Nd of points A, B, C, D and E are 5.6, 6.7, 8.0, 10.0, 13.0 respectively. (5 marks) (iv) Determine the uplift force under the dam. (2 marks) (v) Calculate the factor of safety against piping. Given Lmin = 0.85m. (3 marks)