Experimental study on scouring characteristics of cohesive bank soil in the Jingjiang reach

The erosion-resisting capacity of cohesive soil is relatively strong, with its magnitude determining the erosion rate of cohesive riverbank. It is necessary to obtain the incipient condition, erodibility coefficient, and the relationship between them in order to investigate the erosion-resisting capacity of cohesive soil. Therefore, a series of laboratory experiments has been conducted in a closed rectangular flume for the investigation of incipient conditions and scouring characteristics of a cohesive bank soil sampled from the Jingjiang reach. According to experimental results, the relationship was obtained between incipient velocity and the ratio of liquid limit to natural water content, as well as the quantitative relationship between critical shear stress and dry density, critical shear stress and liqidity index, which accounted for the effects of various physical properties on the incipient motion of cohesive soil. In addition, the variation characteristic of erodibility coefficient with the critical shear stress was proposed for the cohesive bank soil in the Jingjiang reach, and it was found that the obtained erodibility coefficient under the same critical shear stress is much higher, as compared with the value calculated using the existing relations obtained from other river basins, which is attributed to a lower clay content in the study reach and the disturbed soil samples. Based on the results of scouring experiment, a quantitative relationship between the erodibility coefficient and critical shear stress of cohesive bank soil was obtained, with a correlation coefficient of 0.90, which can provide a basis for predicting the erosion process of riverbanks in the Jingjiang reach.