I need a Civil Eng. soil mechanics
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semester_project.pdf
98
Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory) Binod Tiwari, PhD
Stability Analysis of Slopes
Background Evaluating the stability of slopes in soil is an important, interesting, and challenging aspect of civil engineering. Concerns with slope stability have driven some of the most important advances in our understanding of the complex behavior. Extensive engineering and research studies performed over the past 70 years provide sound set of soil mechanics principles with which to attack practical problems of slope stability. There are a number of methods ranging from very simple to highly complicated numerical calculation approach, available for the stability analysis of slopes and a number of computer software are available for the solution. However, very simple methods that can be accomplished through a simple spreadsheet programming are still popular. In this class, we will conduct stability analysis for a
simplified method and compare the results. Simple theory involved in the analysis Ordinary Method of slice For the slope shown in the figure 1,
pn
n nn
pn
n nnn
s
W
CosWLc F
1
1
sin
)'tan'.( (1)
Based on the analysis made on the slope element shown in figure 2,
pn
n nn
pn
n n nn
s
W
m WLc
F
1
1 )(
sin
1 )'tan'.(
, where (2)
s
n nn F
m sin'.tan
cos)(
bn = width of the slice (We need to perform iteration for this analysis)
99
Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory) Binod Tiwari, PhD
Figure 1 Stability analysis by ordinary method of slices
100
Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory) Binod Tiwari, PhD
Stability Analysis for Steady-state Seepage
For steady-state seepage, we need to modify equations 1 and 2 to cover the influence of water. Equation (1) is modified as,
pn
n nn
pn
n nnnnn
s
W
LuCosWLc F
1
1
sin
)'tan)('.( (3)
Equation (2) is modified as
pn
n nn
pn
n n nnnn
s
W
m LuWLc
F
1
1 )(
sin
1 )'tan)('.(
(4)
Information needed
Cross-section of slope Engineering scale Scientific calculator or computer
Procedure
1. Divide the entire slope into a number of equally spaced (or based on slopes) slices.
2. Measure the required parameters and populate the excel spreadsheet (shown in the table below).
3. Calculate factor of safety using the above equations. Compare with two methods.
Figure 3
10 1
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EG CE
3 24
L (S
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F S
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k:
1. P
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at e
th e
fa ct
or o
f sa
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. C on
si de
r un
it w
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t of
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as 1
00 .
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f 1
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or e
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ou nt
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to in
cr ea
se t
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ac to
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s af
et y
to 1
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xa m
pl es
o f
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te rm
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ar e:
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t.
Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory) Spring 2009 Instructor: Binod Tiwari, PhD
104
Example Problem
Simplified Method and
Method of Slice.
Civil & Environmental Engineering Department
EGCE 324L (Soil Mechanics Laboratory) Spring 2009 Instructor: Binod Tiwari, PhD
105
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