复合型滑坡固液耦合过程数值模拟分析--以无山坪滑坡为例

Numerical simulation analysis of the solid-liquid coupling process in a hybrid landslide:A case study of the Wushanping landslide

固液耦合作用是碎屑流向泥石流转化形成复合型滑坡灾害的关键因素,会导致成灾范围和规模放大,是防灾减灾领域研究中的热点和难点问题之一。文中采用自主研发的滑坡后破坏数值模拟平台(LPF 3D,Landslides post failure 3D),以2014年9月强降雨诱发的重庆奉节无山坪滑坡为例,探讨了滑坡在水动力作用下远程成灾的动力过程,揭示了固液耦合影响机制。研究结果显示:水动力作用在滑坡运动过程中主要体现为液化和拖曳两种,两种力学作用的增程效应明显,往往使得碎屑流转化为泥石流,导致远程成灾;基于光滑粒子流体动力学(SPH)方法的两相耦合计算模型,考虑流体状态方程、固体黏塑性本构方程和相间作用力的共同影响,基本还原了强降雨条件下重庆奉节无山坪滑坡两相运动过程;数值计算结果显示无山坪滑坡最大运动速度为34 m/s,最大堆积厚度为21.5 m,堆积面积为0.12 km 2,最远运动距离为1300 m,模拟结果同实际滑坡的堆积形态基本一致。综上认为,在高位远程滑坡风险调查与预测过程中,需充分考虑强降雨工况下孔隙水压力和固液相间作用,基于LPF 3D方法的数值模拟为高位远程滑坡的风险定量评估提供了依据。

The solid-liquid coupling process is crucial in transforming debris flow to mudflow to form a hybrid landslide,which extends the disaster-affected area.It is a hot topic and a tricky problem to be solved in disaster prevention and mitigation research.We used the self-developed post-landslide damage numerical simulation platform(LPF 3D)to explore the dynamic process of the Wushanping landslide induced by heavy rainfall in Chongqing under hydrodynamic action and revealed the solid-liquid coupling mechanism.The results show that hydrodynamic effects in the landslide movement are mainly manifested as liquefaction and dragging.The incremental effects of the two hydrodynamic actions are apparent,which often transform debris flow into mudflow,causing long-runout disasters.A two-phase coupled computational model based on the SPH method is proposed.It restores the two-phase movement of the Wushanping landslide under heavy rainfall conditions considering the combined effects of the fluid state equation,the solid viscoplastic constitutive equation,and the inter-phase forces.The numerical calculation results show that the maximum velocity of the Wushanping landslide is 34 m/s,the maximum accumulation thickness is 21.5 m,the accumulation area is 0.12 km 2,and the farthest movement distance is 1300 m.The simulation results are consistent with the actual landslide′s accumulation pattern.In conclusion,in the high remote landslide risk investigation and prediction process,the pore water pressure and solid-liquid phase interaction under heavy rainfall conditions need to be fully considered,and the numerical simulation based on the LPF 3D method provides a basis for the quantitative risk assessment of high-elevation and long-runout landslides.