الفهرس 
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Abstract
In drainage practice, the problem of draining an agricultural land arises and becomes
a question of survival when the drained land is such that a heavy clay layer with low value of
hydraulic conductivity is underlain by an impermeable barrier. The danger of water logging and
salinity will be more serious. Such conditions may prevail in some areas of the Egyptian lands.
The rational design of a drainage system for the above mentioned areas should be
treated differently, because the spacing between tile drains will be very small and adopting this
system alone will be uneconomical one.
In this thesis the aforementioned problem has been solved by assisting the insufficient
tile drainage system by a system of closely spaced mole drains , laid some distance above the
level of tile drains.
The problem was treated theoretically by the theory of conformal mapping, the complex
functions and the theory of images. Two new discharge formulas were obtained for both mole
and tile drains when working together. A new spacing formula was also presented. A formula
to calculate the water table height after any time interval ( calculated from the moment at which
the irrigation has been stopped ).
A viscous flow model known as the Hele-Shaw model is used in the experimental part
of this work in order to verify the theoretical results.
Although the Hele-Shaw model needs some several precautions in construction and
during experimental runs, the experimental results agree very well, in the most of test range,
with the analytical ones.
Numerous design charts are presented to simplify the use of the developed formulas for practical aDDlications, covering a wide range of the values of the parameters . for steady state flow and unsteady state flow conditions.