Geotechnics – Soil Mechanics
CE2304 Geotechnics – Soil Mechanics Re-sit Coursework (2013/14)
Q1. A cofferdam is constructed to create a dry work environment for
construction of a hydraulic structure. The cross section through the cofferdam
with the length of 40m is shown in the figure Q.1 below. Permeability of the
soil in horizontal and vertical directions is 5 10
⁄ .
a) Draw the flow net for the section of the cofferdam presented in the
figure below [20% of mark]
b) Determine the rate of seepage into the cofferdam [15% of mark]
c) What will be the quantity of water seeped through into the whole
cofferdam in one year’s time? [15% of mark]
Figure Q.1
Q2. A section of an 87m long dam (Figure Q.2.a) and its corresponding flow
net (Figure Q.2.b) are shown below. The hydraulic conductivity value for both
directions for the top soil layer is 3 10
m sec ⁄ and for the bottom soil layer
is 5 10
m sec ⁄ .
Figure Q.2.a
Figure Q.2.b
a) Calculate the scale transformation factor that is used to create the flow
net (Figure Q.2.b) [20% of mark]
b) What is the quantity of seepage per second per unit length of the dam?
[15% of mark]
c) What will be the quantity of water seeping through the whole dam in 5
years? [15% of mark]
NOTE:
– Answer both questions
– Please make sure that you clearly label each section in your answers with the
relevant problem component letter and the question number (i.e. Q1a, Q1b…)
– All the answers must be prepared using MS-Office or any other software of your
choice (handwritten documents are not acceptable except the flow net)
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