Question

50 m Impermeable Concrete dam 6 m 1 m 10 m PtA (at mid-point of layer and centre of base) DATUM Impermeable bedrock Figure 2: Concrete dam (not to scale) Figure 2 shows the cross-section through a long concrete dam in anisotropic soil. The horizontal and vertical permeability of the soil are: K 25 x 10-4 cm/sec and Ky 1 x 10-cm/sec.. (a) Calculate the transform parameter a. In your exam booklet, draw the transformed flow domain to scale and clearly mark the boundary conditions (5 marks) (b) Draw a neat flownet in the flow domain drawn in (a) satisfying the boundary conditions (5 marks) Determine the seepage per day (in m2/sec) per metre length of the dam (c) (5 marks) (d) Determine the pore pressure at Point A (5 marks) Based on your flownet, what is the factor of safety against piping in the critical region of the (e) flow domain if the saturated unit weight of the soil ysat = 19 kN/m3? (5 marks)

Answer 1

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