Most of the landforms in southwest China are high mountains and valleys, which are prone to be dammed by the landslides and form dammed lakes. During the rising of water level, the encountered stress path is constant shear stress, namely the shear stresses was constant, but the pore water pressures increased gradually. Currently, most of the conducted tests of landslide dam were focused on the consolidated drained or undrained tests, it is different from the actual stress path in the process of rising of water level. Therefore, the study on deformation characteristics of the landslide dam under the constant shear stress path is an effective way to deeply analyze the dynamic deformation of the landslide dam during the rising of water level. Hence, taken the Baige dammed lake on October 11, 2018, as an example, considered the height of landslide dam, the highest water level before overtopping, and the actual stress path during rising of water level, parametric studies were carried out based on the micro-scale DEM-PFV coupled simulation to investigate the deformation characteristics of landslide dam materials under different confining pressure, different initial stress ratio, and constant shear stress path. The deformation characteristics of landslide dam during the rising of water level and corresponding micromechanics were revealed according to the macro stress-strain relationship and distribution of contact forces between particles. It suggests that the deformation characteristics of landslide dam materials during the rising of water level is highly dependent on the combined roles of location, strength, and extent of water level. At different locations, the confining pressure and stress ratio is different, and the max pore water pressure is different too. This induced different deformation characteristics during the rising of water level, and usually the deformation increased from the core of the landslide dam to the surface at upstream. At the same confining pressure, the materials closed to the side of landslide dam, the initial stress ratio is high, and the encountered pore water pressure is high, so it will be more easily deformed, and the extent of large deformation is restricted by the initial stress ratio and the final water level, this could be attributed to the weakening of contact forces between particles. At the internal part of landslide dam, the initial stress ratio is lower than the external part, hence the probability of passing the instability line is lower, and the deformation of the internal part is smaller.
