بررسي آزمايشگاهي تنش برشي بحراني فرسايش رسوبات چسبنده شش كانال آبياري در استان خوزستان

Experimental Study of Critical Shear Stress of Erosion of Cohesive Sediments of Six Irrigation Channels in Khuzestan

Resistance to erosion in cohesionless sediment is a result of gravity only, but erosion of cohesive sediment is quite different with cohesionless sediment. Before cohesive sediment can be eroded, the interparticle bond must be broken. Thus, a critical shear stress has to be exceeded before erosion of cohesive sediment can occur. The objectives of this study are ~ to study erosion process and determinaing the critical shear stress of erosion of cohesive sediment collected from bed material of six Khozestan irrigation channels, including Dasht-Evan, Hendijan, Veis, Shadegan, Khalaf-Abad and Voseyleh. For each sample two different experiment series were performed. At first, the samples were analyzed to determine the physical and chemical properties of each sample, and then the hydraulic experiments were run to determine the critical shear stress of erosion for each sample. Experimental results are shown that shear stress of erosion for this channel varied from 0.96 N/M2 in Shadegan channel, to 2.3 N/M2 in Hendijan channel. The main point of this study is that in the areas that the sediments are cohesive, it is very important to find the critical shear stress of erosion and use it as a correct criterion for designing channels and hydraulic structures.