土的剪切空间滑动面分析及各向异性强度准则研究

天然沉积的土往往具有原生各向异性、结构性，以及加载作用下的次生各向异性和结构损伤性，导致土的强度规律变化复杂。通过对Mohr-Coulomb、Druker-Prager和Matsuoka-Nakai强度准则建立基础的分析，提出了定法向剪切空间滑动面和变法向剪切空间滑动面的分类。运用Mohr-Coulomb准则描述土剪切破坏面和Matusoka-Nakai剪切空间滑动面的确定方法，分别建立了轴对称压缩和挤伸两组定法向剪切空间滑动面。依据空间滑动面上抗剪应力与法向正应力呈正比的线性关系，针对轴对称压缩、挤伸剪切空间滑动面，分别建立了各向同性、各向异性条件下土的强度准则，分析了不同强度准则应力空间描述的强度破坏面。针对具有竖向裂隙分布横观各向同性微结构的天然黄土，考虑微结构特征与几何空间坐标轴及主应力轴旋转变化的关系，通过黄土的真三轴试验，揭示了竖向裂隙分布方向分别作用大、中、小主应力的强度变化规律，初步验证了轴对称压缩和挤伸剪切空间滑动面强度准则及各向异性强度准则的合理性。建立的强度准则拓展了传统强度准则关于剪切空间滑动面及各向异性强度规律研究的范畴，能够为土工强度稳定性的分析提供更加符合实际的理论基础。

Several shear spatially mobilized planes and anisotropic strength criteria of soils

The strength laws of natural soils are complex because of their anisotropic and structural properties, and stress anisotropy and damage of structures under loading. By analyzing the shear failure planes or spatially mobilized planes of the Mohr-Coulomb criterion, Drucker-Prager criterion and Matsuoka-Nakai strength criterion, two kinds of spatially mobilized planes, static spatially mobilized plane with unchanging normal direction and dynamic spatially mobilized plane with changing normal direction, are proposed respectively by changing the characteristics of normal direction on the spatially mobilized plane. According to the Mohr-Coulomb failure plane and Matsuoka-Nakai’s spatially mobilized plane, the static axial symmetrical compression spatially mobilized plane and axial extension spatially mobilized plane are obtained respectively under axial symmetrical compression and axial extension stress states. Assuming the linear relation between shear stress and normal stress on the spatially mobilized plane of soil element, the new isotropic and anisotropic strength criteria are established based on the stress conditions of two kinds of static spatially mobilized planes, which are determined respectively by the axial symmetrical compression and axial symmetrical extension stress states. For the intact loess with micro-structural characteristics including vertical crack and transversely isotropic body, the anisotropic strength is revealed by the true triaxial experiments on intact loess, in which the maximum principal stress, intermediate principal stress or minor principal stress act on the vertical direction of loess sample. Considering the relationship between the Cartesian coordinates corresponding to vertical crack of loess and rotation of the maximum, intermediate and minor principal stress axes, the spatial strength surface in the principal stress space being the same as that in the Cartesian coordinates. At the same time, the rationality of the above strength criteria is validated by the true axial test results of intact loess with vertical crack structure. The new strength criteria are analyzed by the geometrical characteristics of strength surfaces in the