Introduction to Soil Mechanics
Spring 2011
Quiz 3a
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Problem 1
Refer to Figure 1. Find the flow rate in m3/sec/m length (at right angles to the cross section shown)
through the permeable soil layer. Given H = 6 m, H1 = 2.5 m, h = 2.8 m, L = 40 m, α = 10°, k = 0.05
cm/sec.
Figure 1.
Problem 2 (Hydraulic Gradient and Darcy's Law)
The constant head permeameter shown in Figure
2 contains three different soils as shown. Their
hydraulic conductivities are:
Soil 1 – k = 9 cm/s
Soil 2 – k = 6x10-2 cm/s
Soil 3 – k = 8x10-3 cm/s
The four piezometer tips are spaced at 100-mm
intervals, and the soil interfaces are exactly
aligned with peizometer tips B and C. The
total heads in piezometers A and D are 98.9 and
3.6 cm, respectively.
Compute the total heads
in piezometers B and C.
Figure 2.
Introduction to Soil Mechanics
Spring 2011
Quiz 3b
Problem 3
Given the flow net shown in Figure 3.
(a) Calculate the rate of seepage under the weir.
(b) Calculate the uplift force at the base of the weir per meter length (measured along the axis) of the
structure.
(c) For points A and B, which one has higher seepage velocity?
37 m
3m
A
9m
B
Impervious layer
Figure 3.
k = 10-3 cm/sec