吕梁山压实花岗岩风化土的强度特性及本构模型

The strength and constitutive model of compacted weathered granite soils in Lüliang mountains

吕梁山花岗岩风化土与长江以南的花岗岩风化土具有较大差异。为了全面认识花岗岩风化土的力学性状,并为合理评价山区路基填料的工程性质提供依据,通过常规物理力学试验和大三轴试验,评价了吕梁山压实花岗岩风化土的基本物理特性和强度特性,发现所研究风化土在较低围压下即表现出颗粒破碎特性。参照既有研究成果,修正了花岗岩风化土峰值应力比M_f和状态应力比M_c的关系,确定了吕梁山压实花岗岩风化土的弹塑性本构模型。基于等向压缩-卸载试验与初始剪切的连续性假定,结合邓肯-张模型,最终获得了修正强度条件下风化土本构关系的所有模型参数。通过比较计算和试验结果,验证了峰值应力比与状态应力比的乘积为平均主应力的幂函数关系的合理性。

The weathered granite soil varies significantly from Lüliang mountains to south of the Yangtze river. To comprehensively understand the mechanical properties of weathered granite and evaluate of the engineering properties of subgrade filling in mountains, a series of laboratory tests was performed in this study, including routine soil test, X-ray diffraction test and large-scale triaxial test. The experimental results show that the increase in peak deviatoric stress q_f due to an increase in mean stress p is observed as nonlinear under lower confining pressure because of the existence of particle breakage. The relationship between peak stress ratio M_f and state stress ratio M_c is modified on the basis of previous research results. the elastic-plastic constitutive model of compacted granite soil in Lüliang mountains is proposed. Based on the continuity assumption of the isotropic compression-unloading test and the initial shear, combined with the Duncan-Chang model, all the parameters of the proposed constitutive model of weathered soil under the modified strength condition were obtained. After comparing the results of numerical calculation of proposed model with the experimental stress-strain data, it is found that the product of the state stress ratio and peak stress ratio was not constant but the power function of average main stress.