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The fluctuations of reservoir water levels significantly change the hydrogeological conditions of reservoir banks and thus affect the steady state of the bank slope. Reservoir landslide stability is governed by the complex interactions between the rock and the water (both reservoir and pore water). This paper establishes the constitutive coupled model of seepage and stress field for the E20 bank slope in the Haizhou Open Pit Coal Mine hydropower station's lower reservoir. Using the geotechnical engineering three-dimensional fast Lagrangian analysis of continua (FLAC-3D 4.0) program as a computational analysis tool, the E20 bank slope deformation mechanism was analyzed. The simulation model, calculated by using the Boit consolidation and pore-water continuity principles, was built using FEMs. The numerical simulation results showed that cyclical fluctuations and speeds of the reservoir's water level affect its bank slope stability. When the water level drops at a speed of 12 m/day, the simulation's calculated safety factor value is 0.99, but when the water level rises at a speed of 12 m/day, the calculated safety factor value is 1.03. The results demonstrated that the rapid drop of the water level had a greater impact on the reservoir bank slope stability than the rapid rise of the water level under the same conditions. [ABSTRACT FROM AUTHOR]

Abstract: Discontinuous deformation analysis (DDA) has been widely applied in simulations of discontinuous blocky systems. The behavior of a discontinuous blocky system is mainly governed by the strength of the interface joints. The Mohr–Coulomb joint failure criterion, adopted in the original DDA, is examined through a classic case of a single block on an inclined plane. It shows that when interface cohesion exists, the block may be unstable even if the interface strength is greater than the theoretical strength required for critical stability, as the cohesion has been improperly removed. Adopting relative displacement between contacted blocks as the criterion for the removal of cohesion will provide more accurate results. The development of DDA with displacement-dependent interface shear strength is presented in this paper. To implement and illustrate the modified algorithm, two examples of progressive landslide failure simulations are performed. Both systems exhibit a two-stage failure pattern: a relatively slow, downward progressive failure stage followed by a rapid, massive run out failure stage. [Copyright &y& Elsevier]