考虑颗粒状态转化的高位远程滑坡数值模拟方法

Numerical simulation method of high-position and long runout landslides under granular state transformation

高位远程滑坡运动过程复杂,滑体状态多变,动力学机制和反演预测技术一直是防灾减灾研究中的重点和难点问题。通过调查分析、理论研究和数值技术研发,揭示高位远程滑坡运动过程中基于密集程度的多态转化动力过程,综合SPH和DEM算法提出基于动力学本构转化的滑坡后破坏(LPF3D)数值模拟方法。研究结果显示:(1)通过实际滑坡视频分析和颗粒滑槽试验记录,认为滑坡运动中具有一定空间效应,滑体颗粒呈现了浓密态、稀疏态、超稀疏态,颗粒状态是时刻变化和相互转化的;(2)采用体积分数作为离散颗粒数量和颗粒状态转化的判别标准,提出不同动力学本构求解滑坡运动中不同状态的数值计算方法和临界体积分数取值;(3)基于多态转化理论的宏观连续介质算法反演了重庆武隆鸡尾山滑坡碎屑流实际案例,模拟结果同实际堆积结果基本一致;(4)LPF3D数值模拟方法在计算滑坡后破坏的运动过程,实现了颗粒状态转化和满足实际颗粒数量的高效计算,并提高了计算收敛稳定性,计算优势明显。综上研究,认为在高位远程滑坡风险调查与动力过程研究分析中,应当充分考虑滑体颗粒状态变化和实际颗粒数量的影响,滑坡后破坏LPF3D数值模拟方法为高位远程滑坡的风险评估预测提供了高效和定量化的可选方法。

The movement process of high-position and long-runout landslides is complex and the sliding main body is changeable.The dynamics theory of post-failure and inversion prediction technology have always been the focus and difficult problems in the field of disaster prevention and reduction.In this paper,the dynamic process of polymorphic transformation based on the degree of density in the movement of high-position and long-runout landslide is revealed by survey analysis,theoretical research and numerical technology development.Based on SPH and DEM algorithm and dynamical constitutive model transformation,a new numerical simulation method for landslide post-failure motion(LPF3D)is presented.The results show that:(1)Through the analysis of actual landslide video and grains chute experiment recording,it is found steric effect which the grains motion in the process of landslide movement mainly present the dense state,dilute state and ultra-dilute state,and the grains state changes and transforms with each other at all times.(2)The volume fraction is used as the criterion of discrete grains number and grains state transformation,and the numerical calculation method and critical volume fraction is proposed to solve different states in landslide movement based on different dynamical constitutive models.(3)The macroscopic continuum algorithm based on the theory of polymorphic transformation is used in the inversion of the debris flow of Jiweishan landslide in Wulong,Chongqing,and the simulation results are basically consistent with the actual landslide accumulation.(4)The LPF3D simulation method achieved the transformation of grains state and the efficient calculation of the actual number of grains in the calculation of landslide failure movement,and improves the convergence stability of the calculation,which has great computational advantages.Based on the above research,it is believed that in the risk investigation and dynamic process analysis of high-position and long-runout landslide flow,the influence of the state changes of sliding body grains and the actual number of grains should be fully considered.The LPF3D simulation method provides an efficient,quantitative and optional method for the risk assessment and prediction of high-position and long-runout landslide.