stability analysis of masonry dam

1. Stability of Masonry Dam
By
Sonam Pandey

2. • Dam is a gravity structure constructed to
store water on its face and whose stability
depends on its self weight
Analysis of masonry dam:
Consider 1 m length of dam,
There are two forces acting on the dam
(1) Water pressure force = area of triangle
ABC i.e.
hw
acting at h/3 from base and
3
/81.9 mKNw 
A
BC
hhP w  
2
1
2
2
1
hP w

3. (2) Self weight of dam:
where a = top width
b = bottom width
γ = weight density of masonry
H
ba
W
2


acting at x distance from AB
 ba
abba
x



3
22
densityvolumeW 

4. Resultant of pressure force and weight:
22
WPR 
Acting at Z distance from AB
To find out Z take moment about the base where R
cuts the base
 XZW
h
P 
3

5. Eccentricity of resultant pressure:
2
b
Ze 

6. Stresses at the base:







b
e
b
W 6
1max







b
e
b
W 6
1min
Is always compressive
may be tensile or compressive (when compressive
when tensile
max
min

7. Condition for Stability of Masonry Dam:
1. Stability against crushing:
epermissibl max
2. Stability against tensile stress: the limit of eccentricity should be
greater and equal to 0, i.e.
0
6
1 
b
e
6
b
e 

8. 3. Stability against sliding:
The sliding is caused by horizontal force
for stability against sliding the frictional force
offered by foundation must be greater than
sliding force
WF 
 tanwhere
P
W
P
F
FOS


1FOSFor stability

9. 4. Stability against overturning:
The dam is likely to turn about its toe, the overturning moment is induced
by the horizontal force P, and the stabilizing moment is induced by weight
Of masonry. Taking moment about toe of dam.
3
h
POverturning moment =
Stabilizing moment =  xbW 
i.e. FOS against overturning =
 
3
h
P
xbW


1FOSFor stability against overturning
b