Shallow slope failures induced by rainfall infiltration occur frequently, and the relevant triggering mechanisms have been widely studied.Rainfall-induced landslides are widely recognized to be caused by increases in ...Shallow slope failures induced by rainfall infiltration occur frequently, and the relevant triggering mechanisms have been widely studied.Rainfall-induced landslides are widely recognized to be caused by increases in soil weight, seepage force and pore water pressure or decreases in soil mechanical properties. However, even when all these factors are considered, some landslides still cannot be explained well. The increased pore water pressure in a slope reduces the effective stress of the soil and may trigger slope failure. Similarly, the pore gas pressure in a slope also reduces the effective stress of the soil but has been neglected in previous studies. As the viscosity of air is nearly negligible when compared with that of water, the pore gas pressure spreads faster, and its influence is wider, which is harmful for the stability of the slope. In this paper, the effects of pore gas pressure are considered in a shallow slope stability analysis, and a self-designed experiment is conducted to validate the force transfer mechanism.Numerical simulation results show that the pore gas pressure in the slope increases sharply at different locations under heavy rainfall conditions and that the pore gas pressure causes a rapid decrease in the slope safety factor. Laboratory experimental results show that the pore gas pressure throughout the whole unsaturated zone has the same value, which indicates that the gas pressure could spread quickly to the whole sample.展开更多
In order to study the stability of friction and contact of the rotating tribological pair system,considering the influence of the changeable factors on the stability,the system dynamics analysis model based on the Lag...In order to study the stability of friction and contact of the rotating tribological pair system,considering the influence of the changeable factors on the stability,the system dynamics analysis model based on the Lagrange equation is firstly established.The surface contact stiffness model is determined on the basis of the fractal theory.The model of the friction torque with velocities is created by using the Stribeck friction effect.The Lyapunov indirect method is employed to explore the eigenvalue problem of the system state equation.The effects of the applied load,the fractal dimension,the fractal scaling coefficient and the Stribeck coefficient on the system stability are investigated in detail.The numerical simulation results demonstrate that the tribological pair system is prone to causing system instability at low speed,and the system instability boundary value decreases when the Stribeck coefficient decreases.The fractal dimension and the fractal scaling coefficient impact the system stability slightly when fractal dimensions are large,and the system instability can be reduced by properly increasing the surface smoothness.Moreover,the system instability evidently increases with the increase in the applied load and the Stribeck coefficient.These achievements can provide a reference and theoretical support for the analysis of the dynamic performance of the tribological pair system.展开更多
In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which...In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.展开更多
基金supported by National Key R&D Program of China (Grant No. 2017YFC1501100)the National Natural Science Foundation of China (Grant No. 51279090)Sponsored by Research Fund for Excellent Dissertation of China Three Gorges University
文摘Shallow slope failures induced by rainfall infiltration occur frequently, and the relevant triggering mechanisms have been widely studied.Rainfall-induced landslides are widely recognized to be caused by increases in soil weight, seepage force and pore water pressure or decreases in soil mechanical properties. However, even when all these factors are considered, some landslides still cannot be explained well. The increased pore water pressure in a slope reduces the effective stress of the soil and may trigger slope failure. Similarly, the pore gas pressure in a slope also reduces the effective stress of the soil but has been neglected in previous studies. As the viscosity of air is nearly negligible when compared with that of water, the pore gas pressure spreads faster, and its influence is wider, which is harmful for the stability of the slope. In this paper, the effects of pore gas pressure are considered in a shallow slope stability analysis, and a self-designed experiment is conducted to validate the force transfer mechanism.Numerical simulation results show that the pore gas pressure in the slope increases sharply at different locations under heavy rainfall conditions and that the pore gas pressure causes a rapid decrease in the slope safety factor. Laboratory experimental results show that the pore gas pressure throughout the whole unsaturated zone has the same value, which indicates that the gas pressure could spread quickly to the whole sample.
基金The Science and Technology Support Program of Jiangsu Province(No.BE2014133)the Transformation Program of Scientific and Technological Achievements of Jiangsu Province(No.201701213).
文摘In order to study the stability of friction and contact of the rotating tribological pair system,considering the influence of the changeable factors on the stability,the system dynamics analysis model based on the Lagrange equation is firstly established.The surface contact stiffness model is determined on the basis of the fractal theory.The model of the friction torque with velocities is created by using the Stribeck friction effect.The Lyapunov indirect method is employed to explore the eigenvalue problem of the system state equation.The effects of the applied load,the fractal dimension,the fractal scaling coefficient and the Stribeck coefficient on the system stability are investigated in detail.The numerical simulation results demonstrate that the tribological pair system is prone to causing system instability at low speed,and the system instability boundary value decreases when the Stribeck coefficient decreases.The fractal dimension and the fractal scaling coefficient impact the system stability slightly when fractal dimensions are large,and the system instability can be reduced by properly increasing the surface smoothness.Moreover,the system instability evidently increases with the increase in the applied load and the Stribeck coefficient.These achievements can provide a reference and theoretical support for the analysis of the dynamic performance of the tribological pair system.
基金The National Natural Science Foundation of China(Grant Nos.61078057,61471301,51172183,51402240 and 51471134)The NPU Foundation for Fundamental Research(Grant No.JC20120246)+2 种基金The National Science Foundation of Shaanxi Province,China(Grant No.2012JQ8013)The Doctorate Foundation of Northwestern Polytechnical University(Grant No.CX201325)The Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20126102110045)
文摘In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.
