|
Abstract A classical elastoplastic constitutive model is generally defined in a 2D or 3D coaxial stress space and has a postulate of normal plastic flow rule. As a result，the classical elastoplastic constitutive relation implicates an inevitable limitation that directions for principal stress and that for principal plastic rate of deformation are always coaxial. Therefore，a non-coaxial constitutive model is indispensable in order to offer an insight into the behaviour of rocks and soils. In this paper，a non-coaxial plastic strain rate is defined；and a framework of non-coaxial model is built based on 3D coaxial stress space. The analysis finds that the classical non-coaxial stress rate，proposed by J. W. Rundnicki and J. R. Rice，is only built on the basis of 2D coaxial stress space but invalid in multi-dimensional stress space since the effect of the third stress invariant on non-coaxiality is ignored. The stress-probe test in multi-dimensional stress space shows that an incremental nonlinear response can almost be observed as the rotation of principal stresses，whilst no non-coaxial plastic strain exists in a true triaxial state. The probe results exhibit a coincident constitutive response with a lot of experimental observations.
|
|
Received: 10 October 2005
|
|
|
|
