中文摘要：

由于传统的弹塑性本构模型是基于二维或三维的共轴应力空间和正交流动法则得到的，从而隐含了应力主方向和塑性应变率主方向共轴的局限性，由此引入非共轴塑性流动理论描述岩土体的本构特性。基于三维共轴应力空间定义多维应力状态下的非共轴应变率，进而建立非共轴本构理论框架。理论分析表明，J．W．Rudnicki和J．R．Rice早期定义的非共轴塑性应变率是基于二维共轴应力空间得到的，由于忽略第三应力不变量的影响，在多维应力空间并不能保证其非共轴性。应力探测试验表明，在多维应力空间伴随着主应力的旋转将产生非共轴塑性应变，而在真三维应力状态下没有非共轴塑性应变产生，这与大量试验观察到的岩土体本构现象是一致的。

英文摘要：

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.