滑坡是自然界尤其是山区经常遇到的一种地质灾害，其强大的破坏力对人民的生命和财产安全构成了巨大威胁。对滑体运动状态和规律的研究，可以为滑坡影响预测和风险防范提供参考，为滑坡防治提供依据。本文基于连续介质理论，将颗粒μ(I)流变准则与连续介质力学的Navier-Stokes方程结合起来，建立了三维滑坡动力学模型，实现了滑坡动力特征和三维运动全过程的模拟，重现了文家沟和白格滑坡的致灾过程，揭示了滑坡的颗粒物理本源机理。本研究基于颗粒μ(I)流变本构关系，结合连续介质力学Navier-Stokes方程，推演了描述三维滑坡运动的质量守恒方程、动量守恒方程，发展了三维滑坡动力学模型。该模型用μ(I)流变准则中的广义摩擦系数来反映滑坡体摩擦特性，用等效运动黏度来反映滑坡体运动时表现出的流体特性，实现了对滑坡体流-固耦合运动状态的描述。相比基于深度平均方法的滑坡模型，该模型可以更详细地反映滑体的三维运动状态。本研究通过引入Tresca、Drucker-Prager以及Mohr-Coulomb等强度准则，实现了μ(I)流变准则中临界摩擦系数与土力学强度参数之间的联系；基于流体体积法（VOF），在相方程中增加逆梯度对流项，对相界面进行捕捉，推导了非混溶两相流及多相流滑坡运动模型，实现了室内试验尺度及天然滑坡尺度下两相流及多相流运动的模拟，可以更好研究滑坡气浪冲击效应和滑床冲击刮擦效应。为求解建立的三维滑坡动力学模型，用有限体积法离散控制方程，使用PISO算法进行迭代得到瞬态场的数值解。基于OpenFOAM开源平台开发了数值求解器，对颗粒流斜面试验、柱体坍塌试验以及天然滑坡实例进行了模拟，数值计算与室内试验及天然滑坡实例的对比验证了模型的有效性。参数敏感性分析表明摩擦系数对滑体运动影响显著。此外，本研究考虑了大型滑坡体空间非均质性及复杂边界效应，研究了多层土体的相互作用，揭示了多层土体滑动特征及复杂边界的影响。对不同结构形式的消能效果进行研究，发现拦挡结构能够有效降低滑体的动能峰值，合理的消能结构可有效减轻滑坡或碎屑流带来的危害，为人工防治滑坡提供参考。
Landslide is a natural geological disaster that often occurs in nature, especially in mountainous areas. People’s lives are under huge threat from disruptive avalanches as well as property security. The research on the state and law of sliding mass movement can provide a reference for landslide impact prediction and risk prevention, and also for landslide treatment. In the dissertation, a three-dimensional avalanche simulation method is developed by introducing the μ(I) rheology into the Navier-Stokes equations of continuum mechanics. The dynamic characteristics of avalanches and the whole three-dimensional process are simulated. The disaster-causing process of Wenjiagou and Baige landslides is reproduced. This simulation method reveals the particle mechanism of avalanches.By combining the μ(I) rheology and the Navier-Stokes equations, the mass conservation equation and momentum conservation equation describing the three-dimensional landslide movement are derived, thus a three-dimensional avalanche dynamic model is developed. The friction coefficients in μ(I) rheology are used to reflect the friction properties of landslides, and the equivalent kinematic viscosity is used to describe the fluid properties of landslides, which realizes the characterization of the fluid-solid coupling motion state of the landslide. Compared with landslide models based on the depth-averaged method, the three-dimensional landslide model can depict the landslide movement in more detail.Based on Tresca, Drucker-Prager, and Mohr-Coulomb criterion, the relationships between the critical friction coefficient and the soil mechanical strength parameters in μ(I) rheology are revealed. The volume of fluid method is used to obtain the phase equation. The inverse gradient convection term is added to the phase equation, which can capture the phase interface. The movement simulation of two-phase flow and multi-phase flow at different scales was realized. It is found that the airblast effects caused by the movement of landslides and the scratch effects on an erodible sliding bed can not be ignored.To solve the three-dimensional avalanche dynamic model, the finite volume method is applied to the governing equations. The PISO algorithm is used to gain the transient field. The solver based on OpenFOAM open-source platform is used to simulate the granular incline test, the column collapse test, and natural landslide processes. The comparison between the numerical calculations and the experiments and the actual landslide verifies the effectiveness of the model. Besides, the results of the parameters sensitivity analysis show that the friction coefficients have the most significant effects on the landslide movement.Furthermore, Considering the spatial heterogeneity of large landslides and the effect of complex boundaries, this paper studies the interaction of multi-layer granular flow, and reveals the sliding characteristics of multi-layer granular flow and the influence of complex boundary. This dissertation studies the energy dissipation effect of different structures. It is found that the dam structure can effectively reduce the peak kinetic energy of the landslide. A reasonable energy dissipation structure can effectively reduce the hazards caused by landslides or debris flow. These can provide a reference for artificial landslide prevention and treatment.
