The non-coaxial model simulating the non-coincidence between the principal stresses and the principal plastic strain rates is employed within the framework of finite element method（FEM） to predict the behaviors of a...The non-coaxial model simulating the non-coincidence between the principal stresses and the principal plastic strain rates is employed within the framework of finite element method（FEM） to predict the behaviors of anchors embedded in granular material.The non-coaxial model is developed based on the non-coaxial yield vertex theory,and the elastic and conventional coaxial plastic deformations are simulated by using elasto-perfectly plastic Drucker-Prager yield function according to the original yield vertex theory.Both the horizontal and vertical anchors with various embedment depths are considered.Different anchor shapes and soil friction and dilation angles are also taken into account.The predictions indicate that the use of non-coaxial models leads to softer responses,compared with those using conventional coaxial models.Besides,the predicted ultimate pulling capacities are the same for both coaxial and non-coaxial models.The non-coaxial influences increase with the increasing embedment depths,and circular anchors lead to larger non-coaxial influences than strip anchors.In view of the fact that the design of anchors is mainly determined by their displacements,ignoring the non-coaxiality in finite element numerical analysis can lead to unsafe results.展开更多
For coarse grained soils,their principal stress directions may change when the water level of embankment dam varies instantaneously.In this loading case,the principal directions of stress and strain rate will become n...For coarse grained soils,their principal stress directions may change when the water level of embankment dam varies instantaneously.In this loading case,the principal directions of stress and strain rate will become non-coaxial.In an effort to model non-coaxial behavior,a modified three-dimensional non-coaxial model is developed in the context of vertex yield(tangent plasticity) theory.Discrete Element Method(PFC) incorporating user-defined interparticle contact models is also employed to gain an insight into microscopic mechanism of non-coaxiality.The analysis focuses on non-coaxial behaviors under simple shear condition.It has been shown that the proposed non-coaxial model gives good predictions for non-coaxiality with reference to microscopic observations while the classical coaxial model fails to simulate the non-coaxial behaviors.In general,non-coaxiality as a result of the rotation of principal stress,is large at a small shear strain,and inclined to become negligible with increasing shear strain.For coarse grained soils,their non-coaxiality tends to largely depend on the initial normal pressure,where a larger degree of non-coaxiality can be observed at a higher pressure.展开更多
基金Supported by an EPSRC grant(GR/S29232/01)from the UK Government
文摘The non-coaxial model simulating the non-coincidence between the principal stresses and the principal plastic strain rates is employed within the framework of finite element method（FEM） to predict the behaviors of anchors embedded in granular material.The non-coaxial model is developed based on the non-coaxial yield vertex theory,and the elastic and conventional coaxial plastic deformations are simulated by using elasto-perfectly plastic Drucker-Prager yield function according to the original yield vertex theory.Both the horizontal and vertical anchors with various embedment depths are considered.Different anchor shapes and soil friction and dilation angles are also taken into account.The predictions indicate that the use of non-coaxial models leads to softer responses,compared with those using conventional coaxial models.Besides,the predicted ultimate pulling capacities are the same for both coaxial and non-coaxial models.The non-coaxial influences increase with the increasing embedment depths,and circular anchors lead to larger non-coaxial influences than strip anchors.In view of the fact that the design of anchors is mainly determined by their displacements,ignoring the non-coaxiality in finite element numerical analysis can lead to unsafe results.
基金supported by the National Natural Science Foundation of China(Grant Nos.5067909,10972159 and 50825803)the Kwang-Hua Fund for College of Civil Engineering,Tongji University
文摘For coarse grained soils,their principal stress directions may change when the water level of embankment dam varies instantaneously.In this loading case,the principal directions of stress and strain rate will become non-coaxial.In an effort to model non-coaxial behavior,a modified three-dimensional non-coaxial model is developed in the context of vertex yield(tangent plasticity) theory.Discrete Element Method(PFC) incorporating user-defined interparticle contact models is also employed to gain an insight into microscopic mechanism of non-coaxiality.The analysis focuses on non-coaxial behaviors under simple shear condition.It has been shown that the proposed non-coaxial model gives good predictions for non-coaxiality with reference to microscopic observations while the classical coaxial model fails to simulate the non-coaxial behaviors.In general,non-coaxiality as a result of the rotation of principal stress,is large at a small shear strain,and inclined to become negligible with increasing shear strain.For coarse grained soils,their non-coaxiality tends to largely depend on the initial normal pressure,where a larger degree of non-coaxiality can be observed at a higher pressure.
