Deterioration-buckling failure mechanism of consequent bedding limestone bank slope in Three Gorges Reservoir area

Abstract

In the Wuxia section of the Three Gorges Reservoir area, it is found that there are many deformation signs of sliding-bending along the bedding bank slope, and the cyclic fluctuation of reservoir water worsens the deterioration and instability of the bank leading edge. Taking Qingshi #6 slope in the Wuxia section as an example, an laboratory generalized model is constructed to study the catastrophe mechanism of bedding limestone bank slope under the deterioration of rock mass in hydro-fluctuation belt. The research shows that: the bank slope is in a stable state as a whole for a long time before impoundment. After impoundment, with the deterioration aggravation of rock mass, the bank slope deformation intensifies until buckling failure. The deterioration of rock mass shortens the instability process of ‘deterioration-buckling’. Kinematic analysis shows that the peak velocity of the same rock stratum is similar during buckling failure. The movement characteristics of the rear part of the ‘buckling point’ of rock mass are relatively consistent, but the front part is relatively discrete. The buckling failure is the turning point and apex of bank slope energy release. Both displacement and stress show signs of premature failure after gradually increasing with deterioration evolution. The stress produces ‘concentration-release’ around the buckling failure. On the whole, the stress variation is earlier than the displacement variation, indicating that the stress monitoring is more effective. The core of stress monitoring is to determine the ‘key section’. For the ‘deterioration-buckling’ bank slope, the sharp increase of stress at the ‘deflection section’ of the front edge can be an important characterization of the critical instability of the bank slope. The trailing edge pushing always exists in the evolution process of ‘deterioration buckling’, which is the premise of bank slope catastrophe failure. However, the dominant factor of bank slope instability is the continuous deterioration of the rock mass in the hydro-fluctuation belt. The Qingshi #6 slope is currently in the process of evolution toward ‘strong bending uplift’, it may gradually evolve from a stable/basically stable state to an understable state, due to the continuous deterioration of the rock mass in the hydro-fluctuation belt.

Keywords

• physical model test
• rock mass deterioration
• consequent bedding limestone bank slope
• deterioration-buckling
• wuxia section of the three gorges reservoir