考虑主应力轴方向的砂土各向异性强度准则与滑动面研究
Strength criteria and slipping planes of anisotropic sand considering direction of major principal stress
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摘要: 主应力加载方向对土体强度产生影响的根本原因是土体存在各向异性。对于横观各向同性砂土而言,沿不同平面的抗剪强度随该平面与沉积面夹角增大而增大。认为砂土固有各向异性强度与该平面的各向异性参数密切相关,给出了各向异性砂的峰值强度表达式。在SMP准则中,各个潜在滑动面上的剪正应力比相同,各向异性砂土的抗剪强度和滑动面位置由强度最低的潜在滑动面所决定。综合考虑主应力轴、滑动面以及沉积面之间的位置关系,得到了砂土的各向异性强度准则。采用福建标准砂进行了一系列定轴剪切试验,系统地观测了定轴剪切试验中试样滑动面的特征。已有试验数据和理论结果的对比表明,各向异性强度准则可以较好地预测各向异性砂土的强度与滑动面位置。Abstract: The effect of directions of the principal stress on the deformation and strength of sand is due to the anisotropy of soils. The shear strength on a certain plane of the cross-isotropic sand is larger when the angle between this plane and the bedding plane is larger. Assuming that the intrinsic anisotropy strength of sand is closely related to the anisotropy parameter of the plane, the peak strength of anisotropic soils is presented. As the shear-normal stress ratio of each potential slipping plane of the SMP criterion is the same, the shear strength and position of the slipping plane are determined by the potential slipping plane with the lowest shear strength. On this basis, an anisotropic strength criterion is proposed by considering the relationship among the principal stress axis, the slipping plane and the bedding plane. A series of shear tests with fixed direction of the major principal stress are carried out using Fujian standard sand in order to systematically observe the slipping plane of the specimens. Comparison between the predicted data and the measured results indicates that the anisotropic model can well reflect the strength and the position of the slipping plane of the anisotropic soils.