中文摘要：

粘性土体具有较强的抗冲能力，其抗冲性强弱决定了河岸的侵蚀速率。为了估算河岸的侵蚀速率，确定粘性土体的起动条件、侵蚀系数及两者之间的数量关系非常重要，为此开展了荆江段河岸粘性土体起动条件与冲刷特性的水槽试验研究。根据试验结果获得了粘性土体的起动流速与土体液限／自然含水率之间关系以及起动切应力与干密度、起动切应力与液性指数之间的定量表达式，综合反映了粘性土起动条件与其物理性质指标之间的关系；结合冲刷特性试验结果，还获得了土体侵蚀系数随起动切应力的变化规律，并与已有其他试验结果进行了比较。结果表明：荆江河岸粘性土侵蚀系数均比相同条件下其他公式计算值偏大，这与该试验土体中粘粒含量相对较低、土体结构受到扰动等因素有关；根据试验结果，拟合得到了荆江河岸粘性土侵蚀系数与起动切应力之间定量关系式，其相关系数R2=0．90，故该关系式能为荆江段崩岸过程的计算提供参考依据。

英文摘要：

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.