基于硬化土模型的小应变本构模型研究

大量的工程现场监测结果表明，城市中强支护隧道施工过程中其周围大部分土体仍处于小应变状态，小应变情况下土体具有显著的高模量和非线性特性。土体小应变刚度特征和应力路径相关性是准确分析土与隧道相互作用的重要因素。虽然采用双刚度的硬化土模型(hardening soil model)能够基本反映应力路径的影响，但其卸载再加载模量并没有与应力-应变水平相关，不能模拟小应变情况下土体模量的高度非线性。为此，结合小应变刚度理论对硬化土模型的卸载再加载模量进行了改进，使之与应力-应变水平相关，并且考虑了土体卸载抗剪强度指标的变化以及侧向卸荷应力路径下不同的模量。通过与土体的应力路径试验结果进行对比，证明了模型的合理性。

A small strain constitutive model based on hardening soil model

A lot of on-site monitoring results show that the soil around many underground constructions is still in a state of small strain under working loads. It is important to consider the soil’s small strain stiffness and stress-path dependency in analyzing interaction between soil and structure. Hardening soil model can define loading-unloading characteristics, however, it can not accurately simulate nonlinear modulus because unloading-reloading modulus is not associated with stress and strain level. In this paper, unloading-reloading modulus of hardening soil model is modified so that it is related to both stress and strain levels; and unloading shear strength and scant stiffness of lateral unloading stress path are also considered specially. Finally, the model results are compared with soil stress-path test results to prove the reasonableness of the model.