27. Bank Collapse Along the Three Gorges Reservoir and the Application of Time-Dependent Modeling

After the Three Gorges reservoir impoundment water level changed, the groundwater dynamic stress field and the rock mass stress field changed considerably. As the water level changes, wave erosion as well as rain storm, causes bank collapse to often occur along the reservoir area. This chapter aims to find the mechanism causing bank collapse and apply this type of information using models which can then describe these mechanisms for later research. In order to find out the relationships between bank collapse and bank width, slope angle, property of bank soil, and intensity of rainfall, some modeling tests were carried out and the results showed that the width of the bank is the main factor affecting bank collapse. Another conclusion is that the process of bank collapse can be characterized as time-dependent. It is proposed that the process be divided into four characteristic phases: surface erosion, shallow erosion, deep erosion, and termination of slope movement. Deep erosion is the key phase of the four, for which the velocity and scale of bank collapses can be calculated.