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为合理模拟主应力轴旋转等复杂加载应力状态,对已有的结构性黏土的各向异性边界面模型中屈服面在π平面上的形状函数M(θ)进行修正,使其适用范围更加广泛,并将模型由三轴应力空间拓展到一般的三维应力空间。通过对天然沉积上海软黏土的一维压缩试验、等压及偏压固结三轴不排水剪切试验、一系列K0固结三轴排水应力路径试验以及不同中主应力系数和主应力轴旋转角度下的空心圆柱不排水剪切试验,对上海软黏土的屈服特性和主应力轴旋转效应进行了系统的研究。试验研究表明天然沉积的上海软黏土具有明显的结构屈服特性和塑性各向异性,初始状态边界面在p′q平面上呈并非以K0线为对称轴的倾斜椭圆形状,临界应力比随中主应力系数的增大而减小,验证了模型中所用的三维边界面方程的合理性;主应力轴旋转对天然沉积软黏土的应力应变关系及强度均有着重要的影响。通过天然沉积上海软黏土等压及偏压固结不排水三轴试验结果对模型参数进行标定,并对应力路径三轴排水试验以及主应力方向旋转的空心圆柱剪切试验结果进行计算,初步验证了拓展后模型在模拟复杂加载路径及主应力轴旋转效应的合理性和有效性。
In order to reasonably simulate the complex loading stress state such as principal stress axis rotation, the shape function M (θ) of the yield surface in the π plane in the existing anisotropic interface model of structural clay is modified to make it more widely applicable , And expand the model from three-axis stress space to the general three-dimensional stress space. Based on the one-dimensional compressive tests of natural sedimentary clay in Shanghai, three-axis undrained shear tests of isobaric and biased consolidation, a series of triaxial tests of K0 consolidation and the different principal stress coefficients and principal axis of rotation Angle hollow cylindrical undrained shear test, the yield characteristics of Shanghai soft clay and the principal stress axis rotation effect of a systematic study. Experimental studies have shown that the natural sediment of Shanghai soft clay has obvious structural yield characteristics and plastic anisotropy, the initial state of the boundary surface in the p’q plane was not the K0 line as the axis of symmetry tilted elliptical shape, the critical stress ratio with the main The stress coefficient increases and decreases, which verifies the rationality of the three-dimensional boundary surface equation used in the model. The rotation of principal stress axis has an important effect on the stress-strain relationship and strength of natural sedimentary soft clay. The parameters of the model were calibrated by the natural sedimentation of Shanghai soft clay under isobaric and undrained consolidated undrained triaxial tests. The results of triaxial tests on stress paths and the results of hollow cylindrical shear tests with principal stress directions were also validated The rationality and validity of the extended model in simulating the complex loading path and the principal stress axis rotation effect.