基于颗粒流数值模型的土质边坡渐进破坏过程仿真分析
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摘要
传统极限平衡法和有限元强度折减法很难真实反映材料的破坏过程,严重制约了边坡的渐进破坏研究。利用颗粒流软件,设计了0.1m粒径高10m土坡数值模型,初始模型在重力作用下不会发生破坏,通过单独折减粒间粘聚力、单独折减粒间摩擦系数和在初始模型上施加0.1g水平地震加速度等3种方法使得边坡发生破坏,发现粘聚力折减,边坡的初始局部破坏接近于刚体假设,破坏属于渐进破坏,滑体破碎较轻,运动距离不远,最终多级组合滑面接近于弧形,不适用整体分析;摩擦角折减使得边坡发生整体破坏,滑体为弹塑性体,滑体破碎,适用整体分析,滑体运动相对较远;地震作用下,坡体也属于整体滑移,滑体破碎,影响范围和运动范围最大。边坡失稳的剧烈程度是地震作用>摩擦角弱化>粘聚力弱化造成的坡体失稳。破坏是个动态渐进势能动能转化消减,滑体再次趋于稳定的重新破碎堆积的过程。
The conventional limit equilibrium and finite element analysis with strength reduction methods have difficulties in simulating the progressive failure of the materials in the slope stability analysis.This disadvantage has impeded the research developments in this area.A 10 meters high soil slope with grain size of 0.1meters was numerically analyzed by the Particle Flow Code software.At its initial stage,the soil slope is stable.Three failure modes have been imposed on the existing soil slope:reduction of the cohesion;reduction of the coefficient of friction among particles and imposing a 0.1g horizontal seismic force on the existing soil slope.30 particle groups with a vertical spacing of 1meter have been monitored for the progressive failure of each 20,000 time step.The progressive failure of a total of 200,000 time steps has been studied.The results indicate that,for the reduction of the cohesion,the initial local failure is close to the rigid body assumption.The failure mode belongs to the progressive failure.The deformations of the sliding body are relatively small and the sliding body movement is not far.The final slip surface is close to an arc.A global failure mode can be found in the reduction of coefficient friction among the particles.The plastic deformations are found in the sliding body and therefore,large deformations are observed in the sliding body.A long distance of movement in the sliding body can be found.Under the seismic condition,the global instability and a broken sliding body can be found.The sliding impact zone and sliding body movement are the largest among three failure modes.The following failure ranking can be obtained from the strongest to the weakest global failure:seismic condition,reduction of internal friction and the reduction of cohesion.The slope failure is a progressive process of reduction of the potential energy and re-stabilization of the sliding body as well as the accumulation of the sliding materials.
The conventional limit equilibrium and finite element analysis with strength reduction methods have difficulties in simulating the progressive failure of the materials in the slope stability analysis.This disadvantage has impeded the research developments in this area.A 10 meters high soil slope with grain size of 0.1meters was numerically analyzed by the Particle Flow Code software.At its initial stage,the soil slope is stable.Three failure modes have been imposed on the existing soil slope:reduction of the cohesion;reduction of the coefficient of friction among particles and imposing a 0.1g horizontal seismic force on the existing soil slope.30 particle groups with a vertical spacing of 1meter have been monitored for the progressive failure of each 20,000 time step.The progressive failure of a total of 200,000 time steps has been studied.The results indicate that,for the reduction of the cohesion,the initial local failure is close to the rigid body assumption.The failure mode belongs to the progressive failure.The deformations of the sliding body are relatively small and the sliding body movement is not far.The final slip surface is close to an arc.A global failure mode can be found in the reduction of coefficient friction among the particles.The plastic deformations are found in the sliding body and therefore,large deformations are observed in the sliding body.A long distance of movement in the sliding body can be found.Under the seismic condition,the global instability and a broken sliding body can be found.The sliding impact zone and sliding body movement are the largest among three failure modes.The following failure ranking can be obtained from the strongest to the weakest global failure:seismic condition,reduction of internal friction and the reduction of cohesion.The slope failure is a progressive process of reduction of the potential energy and re-stabilization of the sliding body as well as the accumulation of the sliding materials.
引文
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[2]BJERRUM D L.Progressive failure in slopes of overconsolidated plastic clay and clay shales[J].J.Soil Mech.&Faund.Div.ASCE,1967,93,3-49.
[3]ZHANG Xianliang.The progressive failure and the stability analysis of slope[D],CENTRAL SOUTH UNIVERSITY,2008.
[4]EBERHARDT E,STEAD D,COGGAN JS.Numerical analysis of initiation and progressive failure in natural rock slopes-the1991Randa rockslide[J].Int J Rock Mech Min Sci 2004;41:69-87.
[5]EBERHARDT E,WILLENBERG H,LOEW S,et al.Active rockslides in Switzerland understanding mechanisms and processes[C].In:International Conference on Landslides Causes,Impacts and Countermeasures,Davos,2001:25-34.
[6]LORIG LJ,CUNDALL PA,DAMJANAC B,et al.A three-dimensionnal model for rock slopes based on micromechanics[C].Proceedings of the 44th US/5th Canada Rock Mechanics Symposium,(Salt Lake City,june 2010),paper no.ARMA 10-399.
[7]LAJTAI EZ.Strength of discontinuous rocks in direct shear[J].Geotechnique,1969,19(2):218-33.
[8]KANEKO K,OTANI J,NOGUCHI Y,et al.Rock fracture mechanics analysis of slope failure[C].In:Deformation and Progressive Failure in Geomechanics,Nagoya,Japan,1997:671-76.
[9]WILLENBERG H,SPILLMANN T,EBERHARDT E,et al.Multidisciplinary monitoring of progressive failure processes in brittle rock slopes concepts and system design[C].In:Proceedings of the first European Conference on Landslides,Prague,2002:477-83.
[10]MIAO TIANDE,MA CHONGWU,WU SHENGZHI.Evolution model of progressive failure of landslides[J].Journal of Geotechnical and Geoenvironmental engineering,ASCE October 1999,827-831;Discussion by K.S.Li,Joley Lam.
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