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Abstract
The problem of seepage from canals is of a great importance to estimate the quantity of seepage loss. The present work is intended to study the problem of seepage from canals with compound sections in which water surface rises above the berm level.
In a canal with compound section, seepage rates increase compared to a traditional canal with simple section. This is due to two reasons; (a) the increase of head difference between water surface in the canal and the groundwater table, and (b) the increase in wetted perimeter and consequently in seepage area. This may lead to a considerable loss of water and low conveyance efficiency.
A computer program, based on the finite element method, it used to obtain the quantity of seepage and to estimate the shape and location of the phreatic surface.
An experimental investigation has been conducted using the viscous flow (Hele-shaw) model to verify the results obtained from the computer program.
In the present study, the considered variables are: the flow depth above the berm level (H), the depth of groundwater table (ho) below canal water surface, the depth of the permeable layer (D), the width of the berin (b), and the side slopes. The obtained results were analyzed as dimensionless curve.
It was found that the relative ground water depth (I1./B), has the most significant influence on the seepage discharge, followed by the relative depth of the permeable layer (D/B), the relative water height above the berm (H/B) and the relative berm width (biB). It was also found that the side slope has a negligible effect on seepage discharge.