Yunyun Fan

The antiperforation performance of protective structures has always been the focus of research in the field of military protection engineering. Because the explicit dynamic finite-element software LS-DYNA is suitable for the simulation of nonlinear and large deformation dynamic processes, it is used in this numerical investigation. The numerical results not only show the perforation process well, but the good agreement with the experiment also confirms the correctness of the numerical results. On the basis of numerical verification, a numerical investigation was carried out on the influence of the impact point, reinforcement ratio, and reinforcement arrangement on the antiperforation performance. The research results show that: (1) due to the discontinuous distribution of the reinforcement and the boundary, the position of the impact point may cause uncertainty in the protection effect, and numerical simulation can help us evaluate this uncertainty; (2) with the same reinforcement ratio, densifying reinforcement is a better method than thickening reinforcement in dealing with the uncertainty of the impact point, so it is more effective; and (3) the reinforcement arrangement has a great influence on the antiperforation performance. With the same amount of material, numerical optimization of the spatial arrangement of reinforcement can effectively improve the protection effect.

Once the slope in the near bank area enters the state of failure, a geological disaster chain caused by landslide and its generated surge occurs very likely. In this study, a two-layer depth-averaged model was used to describe the disaster chain. The HLL (Harten-Lax-van Leer) finite volume method was used for numerical simulation and analysis. Meanwhile, the linear interpolation technique was employed to obtain second-order accuracy. The numerical results of the analytical examples reflect the movement characteristics of the two-layer fluid and verify the correctness of the numerical model. On the basis of numerical verification, the Gongjiafang landslide and its surge were simulated and analyzed. In the early stage, the deformation of the underwater geomaterials disturbed the water, forming the prototype of the surge, and then the landslide movement promoted the rapid development of the surge. After the landslide was deposited, the surge continued to travel forward and formed the largest form near the opposite bank. The numerical simulation is applicable to complex terrain and reveals some mechanisms and characteristics of the disaster chain. Compared with empirical methods, the numerical model adopted could reproduce the process of disasters chain more accurately and effectively and then improve the understanding of the disaster chain. It is feasible that the proposed numerical model can be applied under approximate plane strain conditions but is no longer applicable under 3D conditions. This work can provide reference for further research on disaster chain caused by landslide.

Landslides pose a serious threat to the downstream infrastructure and personnel safety. For situations where the location of possible landslides is difficult to determine, or the potential landslides areas are widely distributed and scattered, passive protective structural measures need to be adopted to relieve the threat of landslides. Taking the Shum Wan Road landslide as an example, the discrete element method was used to reproduce and analyze the landslide movement. On this basis, this study conducts a further numerical investigation on the impact characteristics of the rigid retaining wall used to block landslides. The results show that the numerical back analysis can well represent the evolution of the landslide, and the numerical results are in good agreement with the actual situation, thus confirming its correctness and effectiveness. Under the condition of setting a rigid retaining wall, the landslide can be effectively blocked and form a final deposition behind the retaining wall. The impact on the rigid retaining wall varies with time, and the distribution of the impact in space is also uneven. Through the statistical analysis of the contact forces on the retaining wall, the distributions of static and peak stresses on the retaining wall can be obtained. Compared with the static stability, the spatial distribution of dynamic impact is more difficult to predict, especially the area of the peak impact has a significant influence on the design. Numerical investigation can efficiently and reliably provide abundant information of static stress and dynamic impact on the rigid retaining wall, which can provide important reference for the optimal design of the rigid retaining wall structure.

The Mogangling landslide movement process was numerically simulated in this study and the occurrence and development of the landslide were reproduced. The calculation results show that the Mogangling landslide movement with certain characteristics has experienced several main stages of motion, that is, "front part start, front part acceleration, front part deposition / rear part start and rear part deposition". The obtained final motion distance and the deposition form of the landslide are in perfect agreement with the actual situation, which verifies the correctness and effectiveness of the simulation. This study can provide reference for the prevention and control of landslide disasters.

With the advantages of a simple structure and rapid construction, the rigid netting barrier (RNB) exerts a good obstruction effect on granular flow and is a common engineering measure used to prevent geological disasters in the form of granular flows. However, due to the limitations of current measuring and testing techniques, it is difficult to obtain an accurate measurement of the granular flow velocity and the impact force of granular flow on the mesh structures that are of primary concern in the design of protective structures. To study the characteristics of the obstruction process of RNBs toward granular flow, a typical impact experiment involving granular flow was numerically simulated by the discrete element method, and the correctness and effectiveness of the calculation method were also verified. On this basis, the discrete element method was applied to simulate the obstruction process affecting granular flow under different RNB setting conditions, and the calculation results clearly present the phenomena that occur during the obstruction process of RNBs toward granular flow, such as “run‐up,” “overflow,” “passing‐through,” and “grain‐size segregation.” By analyzing the effects of these phenomena on the obstruction efficiency and the time history of the forces acting on the RNB, the rational setting of an RNB was further discussed. This study can provide a reference for the engineering application of RNB.

This paper presents a clump model based on Discrete Element Method. The clump model was more close to the real particle than a spherical particle. Numerical simulations of several tests of dry granular flow impacting a rigid wall flowing in an inclined chute have been achieved. Five clump models with different sphericity have been used in the simulations. By comparing the simulation results with the experimental results of normal force on the rigid wall, a clump model with better sphericity was selected to complete the following numerical simulation analysis and discussion. The calculation results of normal force showed good agreement with the experimental results, which verify the effectiveness of the clump model. Then, total normal force and bending moment of the rigid wall and motion process of the granular flow were further analyzed. Finally, comparison analysis of the numerical simulations using the clump model with different grain composition was obtained. By observing normal force on the rigid wall and distribution of particle size at the front of the rigid wall at the final state, the effect of grain composition on the force of the rigid wall has been revealed. It mainly showed that, with the increase of the particle size, the peak force at the retaining wall also increase. The result can provide a basis for the research of relevant disaster and the design of protective structures.