初始应力各向异性结构性土的二元介质模型

天然岩土材料具有结构性和各向异性。在岩土破损力学的理论框架下,建立了初始应力各向异性结构性土的二元介质模型。岩土破损力学把结构性岩土材料抽象成由胶结强的胶结块(胶结元)和无胶结的软弱带(摩擦元)组成的二元结构体,变形过程中胶结块逐步破损并向软弱带转化。假定胶结块为横观各向同性的理想弹脆性体,胶结块破损后转化成的软弱带为可用邓肯-张模型描述的非线性弹性体。通过引入考虑各向异性影响的破损率和局部应变系数,建立了初始应力各向异性结构性土的二元介质本构模型,并给出了模型参数的确定方法。最后给出了模型的表现,且通过人工制备初始应力各向异性结构性土的三轴压缩试验结果验证了模型的适用性。计算结果表明,所提出的本构模型可以较好地模拟初始应力各向异性结构性土的应力-应变和体积变形特性。

Binary medium model for structured soils with initial stress-induced anisotropy

Natural soils are structured and anisotropic in the process of sedimentation. Within the theoretical framework of breakage mechanics for geomaterials, a new binary medium model (BMM) for structured soils with initial stress-induced anisotropy is formulated. Breakage mechanics for geomaterials idealizes the structured geomaterials as binary medium consisting of bonding blocks (the bonding element) with strong bonding and weakened bands (the frictional element) without bonding; and the bonding blocks will break and transfer to weakened bands gradually during the loading process. The bonding blocks are assumed as elastic-brittle constitutive model with transverse-isotropy; and the weakened bands transferred from the bonding blocks are assumed as nonlinear elastic Duncan-Chang model. By introducing the breakage ratios and local strain coefficients reflecting the influence of soil structure and anisotropy, the binary medium model for structured soils with initial stress-induced anisotropy is established; and the determination of model parameters in detail is given. Finally the capability of the new model to model the stress-strain properties of anisotropic structured soils is verified and compared with the triaxial tests of artificial structured soils with initial stress-induced anisotropy. The computational results demonstrate that the proposed constitutive model can simulate the mechanical properties, including stress-strain and volumetric deformation, of structured soils with initial stress-induced anisotropy.