Document Type : Research Article
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Abstract
The main objective of this research was to find the stable side slope of irrigation canals, considering type of subgrade materials as well as canal depth. For this purpose two methods of limit equilibrium and finite element methods were used for stability analysis. In respect to the geotechnical properties of subgrade materials, the Unified Soil Classification System as well as the technical properties of each soil group such as cohesion, angle of internal friction and unit weight was used based on the recommendations given in the literature. To consider operation conditions, three cases namely: steady seepage, rapid drawdown and end of construction of canal were taken in to consideration. The results of investigation showed that stability of side slopes in canals is a function of type of subgrade material in respect to its cohesiveness, operation conditions and depth. In non-cohesive materials, the safety factor is not related to the canal depth and is normally less. Based on the mentioned functions safety factor of side slopes of canals with depth up to 8 meters were calculated. For non-cohesive soils stable slopes were about 1:0.6 and for cohesive soils it was determinate around 1:3.
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