针对上下负荷面本构模型不能描述土体应力诱导各向异性和小应变下土体剪切模量衰减特征问题,采用g(θ)方法并结合小应变下经典刚度理论对原始上下负荷面本构模型进行改进,并将改进后的新模型用于预测上海软土、Fukakusa黏土、合肥微膨胀土的三轴剪切试验结果以及模拟合肥地铁徽富路站深基坑开挖工程。结果表明:新模型能够较好地反映土体小应变条件下较高的初始剪切模量以及其非线性衰减特征,能够统一应用von Mises、Mohr-Coulomb、Matsuoka-Nakai和Lade-Duncan四种屈服准则以表征土体的应力诱导各向异性,且能够较好地描述软土的结构性剪缩软化以及超固结土的剪胀软化特性;改进的模型能够很好地表征天然土体复杂力学行为,也较好地预测了基坑开挖过程中支护桩的变形。
To overcome the limitations of the conventional super-subloading surface constitutive model in capturing soil stress-induced anisotropy and the nonlinear degradation of shear modulus at small strains, this study presents an enhanced model. By incorporating the g(θ) method and integrating classical small-strain stiffness theory, the proposed model offers improved representation of both anisotropic behavior and the nonlinear shear modulus reduction under small-strain conditions. The new model was subsequently applied to predict triaxial shear test results for Shanghai soft clay, Fukakusa clay, and Hefei slightly expansive clay, as well as to simulate the deep excavation of the Huifu Road Station in Hefei Metro. The results demonstrate that the proposed model effectively captures the high initial shear modulus and its nonlinear attenuation under small-strain conditions, unifies the application of four yield criteria (von Mises, Mohr-Coulomb, Matsuoka-Nakai, and Lade-Duncan) to characterize stress-induced anisotropy, and successfully describes both the structural shear-shrinkage softening of soft clay and the shear-dilation softening of overconsolidated soil. The improved model not only effectively characterizes complex mechanical behaviors of natural soil but also accurately predicts deformation patterns of retaining piles during excavation processes.
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