FDEM simulation study on deterioration characteristics of weak-hard interbedded strata landslide-anti-slide pile system under wetting-drying cycles

[Objective]In Zigui Basin of the Three Gorges Reservoir region, prone-sliding strata mainly composed of weak-hard interbedded strata are widely distributed. Under the action of long-term reservoir water immersion, erosion and rainfall, the formation rock and soil bodies deteriorate and become an important internal cause of reducing landslide stability and affecting project safety. [Methods]Taking rock and soil mass of weak-hard interbedded strata as the research object, fi-nite discrete element method (FDEM) is used to calibrate the mechanical properties of hard and soft rocks in the weak-hard interbedded strata under different wetting-drying cycles. Then the mesh is redivided by the improved Tyson poly-gon program, and the embedding function of zero thickness cohesive force unit is realized. The FDEM numerical model of landslide-anti-slide pile system in weak-hard interbedded strata formation is proposed and established. Finally, the formation process of landslide cracks and the embedding mechanism of anti-slide piles under different wetting-drying cycles are studied. [Results]The results show that: ① The number of simulated landslide cracks increases with the in-crease of the number of wetting-drying cycles, and the cracks width also increases gradually. The results of simulation are basically consistent with those of the site of Majiagou landslide; ② The simulated cracks of the landslide-anti-slide pile system show two evolutionary patterns: one is that the cracks spread downward from the rock mass on the top side of the pile along the pile body; the other is that the cracks gradually extend from around the anti-slide pile to the inside of the slide body, connecting with the transverse cracks and vertical cracks, and finally forming large through cracks; ③ When the number of wetting-drying cycles increases, the horizontal displacement, bending moment and shear force of anti-slide pile also increase; ④ The cracks in the weak-hard interbedded strata bedrock of the anti-slide pile have the characteristics of localized development, and with the increase of the number of wetting-drying cycles, the stress in the region gradually decreases, the displacement and strain gradually increase, and the corresponding cracks become more and more intensive. [Conclusion]The results of this study can provide support for the prevention and control of land-slide in weak-hard interbedded strata under different wetting-drying cycles.