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天然沉积土大多处于复杂三维应力状态.建立岩土材料三维本构模型的方法(三维化方法)应满足热力学定律这一基本物理规律.本文通过引入与塑性剪应变相应的迁移应力,使基于耗散能增量函数建立的岩土材料本构模型能合理地描述偏平面的三维屈服特性.同时,给出了耗散应力空间应力张量与真实应力张量之间的关系表达式,使本构模型能在三维耗散应力空间中采用相关联的流动法则计算不同应力方向的塑性应变.其次,在热力学框架下对比分析了常见三维化方法的热力学本质,如直接引入强度准则的方法、g()方法和变换应力方法等.说明了三维耗散应力空间与变换应力空间的等价性,验证了变换应力方法在热力学框架下的合理性,同时指出直接引入强度准则的方法和g()方法的不合理之处.最后,通过模型预测值与试验值的比较,验证了建立的三维耗散应力空间及其等价的变换应力空间的适用性.
Most of the natural soils are in the state of complex three-dimensional stress.A method to establish the three-dimensional constitutive model of geomaterials (three-dimensional method) should satisfy the basic physical laws of thermodynamics law.In this paper, by introducing the migration stress corresponding to plastic shear strain, The constitutive model of geomaterials established by the incremental energy function can reasonably describe the three-dimensional yield characteristics of the plane surface. At the same time, the expression of the relationship between the stress tensor and the stress tensor in dissipative stress is given, The model can calculate the plastic strain in different stress directions by using the associated flow laws in the three-dimensional dissipative stress space.Secondly, the thermodynamic properties of the common three-dimensional method are compared and analyzed in the frame of thermodynamics, such as the direct introduction of intensity criterion, g () Method and transformation stress method, etc. The equivalence between the three-dimensional dissipation stress space and the transformation stress space is demonstrated, the rationality of the transformation stress method under the framework of thermodynamics is verified, and the direct introduction of the strength criterion and g () Method is unreasonable.Finally, through the comparison between model predictive value and experimental value, we verify that the established three-dimensional dissipative stress space and Applicability equivalent transformation in stress space.