(Solved): Question 4 (28 marks) (a) The constant head permeameter shown in Figure Q4(a) ...

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Question 4 (28 marks) (a) The constant head permeameter shown in Figure Q4(a) is used for the determination of the permeability of a soil sample. The cross-sectional area of the sample is $$46{\mathrm{cm}}^2$$, the vertical distance (l) between the two manometers is $$10\mathrm{cm}$$, and the difference between the readings on the manometers $$(h)$$ is $$7\mathrm{cm}$$. If $$4\mathrm{ml}$$ of water was collected at the bottom of the permeameter after 10 minutes from the start of the test, calculate the permeability $$k$$. (10 marks) Figure Q4(a) (b) Which laboratory method would you suggest for the determination of the permeability of a clay? (3 marks) (c) Figure Q4(c) shows a sheet pile driven in a silty sand layer overlying impermeable bedrock. The permeability of the silty sand layer has been determined as $$k=2\times 10^{?4}\mathrm{cm}/\mathrm{s}$$. A head of $$5\mathrm{m}$$ separates both sides of the sheet pile. i. Sketch the flow net. (10 marks) ii. Determine the quantity of seepage water per day per metre (i.e. out-of-plane width) of the structure. (5 marks) Figure Q4(c)