In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility...In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.展开更多
Tunnel collapse presents a serious threat to the safety of urban construction. The traditional approach adopted to assess this risk is to evaluate the factor of safety against failure. However, this analysis only dete...Tunnel collapse presents a serious threat to the safety of urban construction. The traditional approach adopted to assess this risk is to evaluate the factor of safety against failure. However, this analysis only determines on whether the tunnel will collapse or not, and does not provide information on the magnitude of the post-failure behavior(for example, catastrophic or progressive) if the tunnel collapse occurs. In this study, a meshless method based on the material point method(MPM) was used to investigate the post-failure behavior of tunnel heading collapse in two-dimensional plane-strain conditions. The capability and accuracy of MPM were verified by comparing the elicited results to centrifuge test data and to analytical solutions obtained from limit state methods. MPM simulations were conducted at different soil conditions(clay or sand) and profiles(homogenous or linear increasing strength) as well as at different tunnel geometries(i.e. tunnel depth and unlined length). The differences in the post-failure behavior and mechanisms are examined and reported.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant no.U22A20603)Sichuan Science and Technology Program-China(Grant No.2023ZYD0149)CAS"Light of West China"Program-China(Grant No.Fangwei Yu).In addition,a special acknowledgement should be expressed to a famous Chinese television drama:My Chief and My Regiment that accompanied me(Dr.Fangwei Yu)through the loneliness time of completing this study.
文摘In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.
基金supported by China Postdoctoral Science Foundation(Grant No.2014M561186)the National Basic Research Program of China("973"Project)(Grant No.2010CB732106)+1 种基金the National Natural Science Foundation of China(Grant No.51308389)the Tianjin Research Program of Application Foundation and Advanced Technology(Grant No.14CQNJC07500)
文摘Tunnel collapse presents a serious threat to the safety of urban construction. The traditional approach adopted to assess this risk is to evaluate the factor of safety against failure. However, this analysis only determines on whether the tunnel will collapse or not, and does not provide information on the magnitude of the post-failure behavior(for example, catastrophic or progressive) if the tunnel collapse occurs. In this study, a meshless method based on the material point method(MPM) was used to investigate the post-failure behavior of tunnel heading collapse in two-dimensional plane-strain conditions. The capability and accuracy of MPM were verified by comparing the elicited results to centrifuge test data and to analytical solutions obtained from limit state methods. MPM simulations were conducted at different soil conditions(clay or sand) and profiles(homogenous or linear increasing strength) as well as at different tunnel geometries(i.e. tunnel depth and unlined length). The differences in the post-failure behavior and mechanisms are examined and reported.
