A graduated student Mohammed Aaed Hassan
obtained master's degree in water resources engineering from the
department of construction and building engineering / university of
Technology with the degree very good for his thesis entitled:
"The behavior of water tanks during sudden filling and sudden discharge
of soil dams
in the discussion that was held at the Hall of the deceased Prof Dr.
Nema Hamad Aumara.
The discussion committee consisted of professors: Assistant Prof. Dr.
Jafar Sadiq Matouk from the Department of Building and Construction
Engineering at the University of Technology (as apresident) and
Assistant Prof. Dr. Thaer Jabbar Mezher from the Faculty of Engineering
at the University of Babylon, Assistant Prof. Dr. Falah Hassan Raheel(as
members) ,Assistant Prof. Dr. Mohamed Yousif Fatah and Assistant Prof.
Hassan Ali Omran, from the Department of Building and Construction
Engineering at the University of Technology(as supervisors).
This study use the method of specified elements to study the leakage
through the soil dam body. So Geostudio program 2007 was used in its two
branches W / SEEP and W / SLOPE. The water levels on both sides of the
tank , downstream, the material properties and the specific conditions
of the dam are the variable inputs, while the amount of water exuding
and gradient exist and pore water pressure are the required outputs of
the program. The output results were compared W/SEEP with calculated
data. It has been verified from the program by the way of analyzing two
models that have been previously analyzed using the method of (flow
net).
Eight nodes elements were used to analyze the dam and its foundations,
while an infinite elements have been used to specify the limited
conditions of the studied case.
In this study, An analysis was made for many heterogeneous soil dams and
analysis of each case in several periods of emptying the tank, included
Al-Wand Dam, Mandawa Dam, Al-Ethaem Dam. Accurate results were found by
the use of Mandawa Dam and AL-Ethaem Dam in that it was found that the
best case was made during the original discharge period of the tank. It
was concluded that when the tank was emptying rapidly, the pore pressure
of water in the body of the dam was declining for two reasons:
First, there is the slow dissipation of pore water pressure due to the
discharge.
Second, there is a flexible immediate effect due to the removal of water
pressure.
During the sudden fall in the level of the tank, the pore water pressure
at all points within the body of the dam is lowered linearly which prove
that the steady-state appeared in clear picture through this down. Some
points in the body of the dam in the background area of the dam may be
affected because of the negative pore water pressure during the descent
of water, which shows that the water level becomes less than these
points.
The (exit gradient) in the back of the dam was decreased during the
descent of water, which means that the safety factor against seepage
will increase with the passage of time. When the emptying period of the
tanks was long(about 10 days), the value of (exit gradient) will become
higher than the previous one.
The flow rate in the back of the dam will increase with time, this
increase occurred because of the rapid flow of water caused by emptying
the tank in a short period. Overall water flow decreases linearly with
time and with the water level in the tank which shows that the flow rate
in the body of the dam appears regularly .
The factor of safety against sliding of the dam slopes decreased little
in short period of time after the start of the sudden drop in the water
tank, then begins to increase. This occurs because the pore water
pressure dissipation after the start of discharge which leads to
increase the effective pressure in the soil, thereby increasing the
shear power inside the soil. Saturated slope of weight produces shearing
stresses while shear strength significantly reduced due to the growth of
pore water pressure that does not dissipate rapidly .
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