Question

2. A cylindrical sample of soil is confined in a rigid-wall permeameter and measures 10 cm in diameter and 20 cm in length. The axis of the cylindrical sample lies in a horizontal plane. They hydraulic head at the left end of the specimen is controlled by a reservoir; the water surface in the reservoir is exactly 100 cm above the horizontal axis of the cylindrical soil sample and remains at 100 cm through a system that automatically adds water to the reservoir if any flows out of the reservoir. The other (right) end of the soil specimen drains through a tube with a valve. When the valve is closed, there is no flow of water. When the valve is open, water can flow through the soil. The tube and valve are located along the projection of the central axis of the sample. When the valve is open, water drips out of the tube such that the water is at atmospheric pressure at the elevation of the central axis of the sample. When the valve is open, water drips out of the tube such that the water is at atmospheric pressure at the elevation of the central axis.

a. When the valve is closed, what is (1) the hydraulic gradient across the sample, (2) the pressure head at the geometric centroid of the soil sample, and (3) the pore water pressure at the centroid of the sample? Note that the unit weight of water is 9.81 kN/m3

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b. When the valve is open, what is (1) the hydraulic gradient across the sample, (2) the pressure head at the geometric centroid of the soil sample, and (3) the pore water pressure at the centroid of the sample?

c. Open standpipes are attached to the permeameter along the upper boundary. The standpipes are 1.2 m tall and are installed at the quarter points. Draw a sketch showing the standpipes and indicate the water levels in the standpipe when the value on the effluent side of the specimen is open.

d. The soil has a hydraulic conductivity of 0.001 cm/sec. With the valve open, how much water (in units of mL) will flow through the soil sample in 5 minutes?

Answer 1