6.1
A coarse-sand sample, 12 cm long and 7.3 cm in diameter, was tested in a constant-head permeameter under a head
of 100 cm for 1 min 12 s. The quantity discharged was exactly 5 liters. Determine the coefficient of permeability.
6.2
How much water, per hour, would pass through a mass of soil described in Problem 6.1, if the mass is 60 cm long
and 100 cm2 in cross section, under a constant head of 2 m?
6.3
A constant-head permeability test is run on a soil sample 9.6 cm in diameter and 20 cm long. The total head at one
end of the sample is 100 cm; at the other end the head is 26 cm. Under these conditions the quantity of flow is
determined to be 20 cm3/min. Determine the coefficient of permeability.
6.4
How much water, per minute, would flow through the mass of soil in Problem 6.3 if the length was changed to 30 cm
and the distance between the head-water and tail-water surfaces was 174 cm?
6.5
A constant-head permeability test was run on a soil sample 7.3 cm in diameter and 14 cm long, Q = 10 cm3/min, h=
100 cm. The soil (grains) has a dry weight of 985 g, a specific gravity of 2.7, and a void ratio of 0.610. Determine:
(a)
The coefficient of permeability.
(b)
The seepage velocity vs.
(c)
The superficial velocity v.
6.6
Determine the quantity of flow per minute through a soil sample 7.3 cm in diameter and 28 cm long under a constant
head of 100 cm if the coefficient of permeability is 5x 10-5 cm/s.
6.7
A falling-head permeability test was run on a soil sample 7.3 cm in diameter and 18 cm long. The diameter of the
standpipe was 1 cm. The water level in the standpipe dropped from 65 cm to 50 cm in 3 hr 13 mm. Determine the
coefficient of permeability.
6.8 How much would the water level in Problem 6.7 be expected to drop in 6 hr?
6.9 A falling-head permeability test was run on a soil sample 9.6 cm in diameter and 10 cm long. The head at the start of
the test was 90 cm. Determine how much head was lost during the first 30 mm if the coefficient of permeability of
the soil was found to he 5 X 10-6cm s. The diameter of the standpipe was 1 cm.
6.10 How much water would flow through the soil sample of Problem 6.9 in 30 mm under a constant head of 90 cm?
6.11 The quantity of discharge from a constant—head permeability test of a sandy silt averaged 23 cm3 mm during the first
few minutes arid 26 cm/mm later. Assuming the test setup to be as represented in Fig. P5.11, determine:
(a) The coefficient of permeability that you feel is most reliable for this sample if h = 100 cm.
(b) Explain the probable reasons for the difference in discharge quantities given above.
(c) Which discharge of the two is probably more representative of the permeability characteristics of the soil ?
6.12 The coefficient of permeability of a soil sample to be tested under a falling-head test setup schematically shown in
Fig. P5.12 is 4.3 X 10-6 cm s. How long would it take for h to be reduced from 200 to 160 cm ?
6.13 A 16-cm-diameter perforated casing is sunk in a sandy stratum a depth of 13 m below the water table to an
impervious stratum. Two observation wells were installed at 20 m and 40 m distance from the test well. During
steady-state pumping of 200 liters/mm the water level in the two wells was lower by 145 and 125 cm, respectively.
Determine the coefficient of permeability.