The Influence Of Rock Mass Degradation On The Evolution Mechanism Of Bank Slope Deformation And Instability

This thesis takes the right bank slope of Yangtze River in Yunyang County of Three Gorges Reservoir as the research object to study the mechanical response of the slope under the action of water-rock cycle and the degree of influence on the deterioration of the mechanical properties of the slope and the impact on the safety of the slope.In this study,the evolutionary mechanism of slope deformation and damage caused by rock deterioration is analyzed by means of visit investigation,experimental research and numerical simulation.The results of the study show that the deterioration of the bank slope under the significant rise and fall of the reservoir water level will lead to a different mechanical response from that of the general rock mass,and the degree of influence on the deterioration of the mechanical properties of the bank slope rock mass and the degree of influence on the safety of the bank slope are also different.The main conclusions are as follows:(1)After visiting and investigating the right bank of Yangtze River in Yunyang County,Chongqing,it is concluded that the damage modes of bank slopes in the study area are mainly divided into three types:(1)weathering-exfoliation type;(2)erosion-exfoliation type;(3)slip type.In the study area,the damage pattern of the bank section of Longsheng Reservoir is mainly of the slip type,while the front edge of the bank is locally steeper with the erosion-exfoliation type and weathering-exfoliation type.The damage pattern of the bank section of Hongping Reservoir is erosion-exfoliation type.The damage pattern of the bank section of Liangshuijing reservoir is mainly of slip type,and the topography of the front edge of the bank is locally steeper with erosion and denudation type.The damage pattern of the bank section of Shenling is mainly of weathering-erosion type,and the local bank is of slip type.The damage pattern of Taoping bank section is erosion-exfoliation type and weathering-exfoliation type.The damage pattern of Xinjin bank section is erosion-exfoliation type.(2)In order to study the relationship between the number of water-rock cycles and the mechanical strength of rocks,water-rock cycle tests and triaxial tests were conducted on the mudstone and sandstone in the study area.The experimental results were analyzed and processed,and the peak stress and shear strength indexes of sandstone as a function of the number of water-rock cycles were obtained by mathematical curve fitting of the experimental data,and the peak stress and shear strength indexes of mudstone as a function of the number of water-rock cycles could also be obtained.(3)In order to study the relationship between slope stability coefficient and water-rock circulation,the slope of Sunjiaping in the study area was selected for numerical simulation.The numerical simulation of the stability coefficient of the slope using the strength reduction method shows that the stability coefficient of the slope decreases with the increase of the number of water-rock circulation in both the case without considering the structural surface and the case with considering the structural surface,but the damage patterns of the two cases are slightly different.It is also found that there is a functional relationship between the stability coefficient and the number of water-rock circulation in both cases,and the functional relationship between the stability coefficient and the number of water-rock circulation is obtained by mathematical fitting,and then the inverse calculation can tell how many times the slope will be damaged after the water-rock circulation.