TYPES OF TYPICAL BANK SLOPE COLLAPSES ON THE THREE GORGES RESERVOIR

The geological investigation at the Three Gorges Reservoir has shown that the bank slope-collapses under different riverbank structures have substantial differences.Based on the field investigation and analysis,the typical bank slope collapsess can be classified into the following five types:(a) washing and abrasion type,(b) soil collapse type including wave washing step type,backward collapsing type and cave collapsing type,(c) rock sliding type including rock block sliding type,up hard-down soft type and down concave type,(d) slope type including renew ancient slide,deep talus only superficial soil sliding type,along bedrock-cover sliding type and bedding sliding type, and(e) flowing soil type.Based on the classification,the further examination are presented.They include the evolutionary processes,,development and distribution characteristics,and relationship with soil structures,landform,and geomorphy.Finally the general geological conditions for forming typical bank slope-collapses are summarized.