A study of the deterioration effect of limestone bank slope rock mass at the Wuxia section of the Three Gorges Reservoir area

The periodic fluctuation of water level elevation between 145 and 175 m is formed due to the Three Gorges Project, which leads to the increasein deterioration damage and reductionin stability of the limestone reservoir slope in the Three Gorges Reservoir area.The limestone bank slope at the Wuxia section is affected by long-term physical and chemical actions, and the macroscopic deterioration is mostobvious. Local consequent bed slope bottom is degraded by erosion and is stripped away, and rock strata are exposed, leading to potential slip-tension failure.The macro-micro deterioration of rock mass surface was quantitatively observed by using 3D laser scanning point cloud technology. It is found that the deterioration of rock mass was mainly along the weak structural planes such as the muddy filling strips. The differential deterioration effect of knife-cut grooves in situ is closely related to the corrosion resistance of dolomite and calcite.The indoor dry-wet cyclic deterioration experiments further show that the deterioration rate of T1d argillaceous strip limestone is significantly higher than that of T1j dolomitic limestone, which is related to the mineral compositions and pore microstructure of the two lithologies. With the increasing cycle period, the mechanical properties of the two rock samples show different degrees of attenuation. Based on the general governing equation regression of nuclear decay deterioration, R2 is as high as 0.861 9~0.999 3. Two kinds of lithological deterioration characteristics are described by introducing the deterioration constant λ and half-life T1/2. It is found that the deterioration constant λ and half-life T1/2 corresponding to different physical parameters of the same lithology are different, showing a “cluster” distribution, which is consistent with the indoor experimental data. When using the deterioration control equation obtained from laboratory experiments, it is necessary to consider that the deterioration of rock mass will be accelerated due to the existence of various structural planes in the field, and the deterioration control equation and mechanical strength need to be reduced accordingly. In this paper, a deterioration control equation based on nuclear decay with clear physical meaning is constructed according to the macro-micro deterioration phenomena in situ and the indoor dry-wet cycle experiment, which may provide a reference for the evaluation, prediction and stability analysis of similar limestone bank slope deterioration in the Three Gorges Reservoir area and in the world.