الفهرس 
CHAPTER (1) INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 157 |  |  |
| | | from | 157 | | |
Abstract
The present study is intended to study the problem of seepage beneath a gravity hydraulic
structure when subjected to local scour. Study aims at investigating the effect of scour hole
position, length, depth, and shape on the seepage characteristics such as potential along the
floor, seepage discharge, and the exit gradient.
Flowing water on the bed line downstream of a hydraulic structure may transport the soil
particles, forming the stream bed, leading to a local scour which is expressed by existence
ofa scour hole. The scour hole takes different shapes, in the present study. Four shapes are
considered which are rectangular, trapezoidal, triangular, and segmental circular shape.
Formation of this scour hole changes the condition of the downstream. bed, which presents
the exit face of seepage, from the straight line to it locally lowered line. Such a change in
the seepage exit surface may affect the seepage characteristics beneath the structure and in
turn affects its stability and lead it to failure.
The problem under consideration here deals with effect of scour hole location, dimensions,
and shape on the seepage characteristics represented by the potential head (h) along the
structure floor, the seepage quantity (q), and the hydraulic gradient (1) along the exit face.
In the present work, the problem of seepage beneath a hydraulic structure followed by a
scour hole had been numerically investigated using the finite elements technique. The
finite elements model was checked using the analytical solutions for some idealized
seepage problems previously investigated and the results were close. Moreover, some
cases are verified experimentally using a Hele-shaw model. These cases were chosen to
represent different cases of the considered parameters.
A computer program, based on the finite elements method, was used to handle with the
input and output data. The input data is the location of scour hole with respect to the
structure floor (Xs), the lower length of the scour hole (Bs), and the maximum scour deI?th
(Ys). The output data is the potential along the floor (h), the seepage discharge (q), and exit
gradient (1).
Result of the study indicated that formation of scour hole, greatly affects the seepage
characteristics beneath such structure, which in turn affects their stability. Also, the
obtained results were graphically presented in a dimensionless curves and charts to be
easily used by designers and researchers.
XI