Will Chair-Like Landslides Undergo Overall Sliding? Insights from Energy Dissipation: A Case Study of the Bazimen Landslide

Chair-like landslides are widely distributed in the Three Gorges Reservoir Area and commonly exhibit episodic deformation under long-term reservoir regulation and rainfall. However， whether such repeated deformation can progressively evolve into overall sliding remains unclear. Taking the Bazimen landslide as a case study， this study employs an energy-based discrete element framework to investigate the work done by gravity and external forces， internal energy transformation， and irreversible dissipation under prescribed historical reservoir water-level and rainfall forcing. Field observations of representative chair-like landslides in the reservoir area indicate that displacement increments are frequently associated temporally with reservoir drawdown and rainfall， while relatively high deformation rates commonly occur in the middle-rear steep zones. In the Bazimen model， the normalized residual critical failure energy of the gentle-section shear band gradually decreased during the initial reservoir water-level cycle and subsequently fluctuated within a narrow positive range. Meanwhile， energy evolution within the shear band was governed primarily by irreversible dissipation in the steep section， whereas changes in tangential elastic energy in the gentle section contributed only a minor fraction of the net energy input. Accordingly， under the adopted linear-elastic contact model and prescribed historical hydrological loading， the Bazimen model exhibited cyclic deformation but did not reach the threshold for throughgoing failure. A one-factor sensitivity analysis further showed that the residual critical failure energy per unit volume in the gentle section varied non-monotonically with the inclination of the steep basal section， initially increasing and then decreasing， with a maximum at an intermediate inclination. Component decomposition attributed this response to the changing balance among normal compression， initial shear resistance， and current shear force. Increasing the steep-section inclination enhanced both the downslope driving component and compressive stress transfer toward the gentle section， thereby precluding a simple monotonic relationship between steep-section inclination and landslide stability. These findings provide a case-specific energy-based complement to conventional stability assessment of chair-like landslides.