粒料的正交异性非线性回弹特性研究

粒料的回弹力学特性具有非线性和正交异性。为研究此特性，设计了一种综合考虑粒料应力依赖性和正交异性的动态回弹特性解决方案，该方案包含：改进的重复加载三轴试验方案、正交异性系数α、Uzan应力依赖模型。改进的试验方案包含多个应力水平，每个应力水平上通过施加应力扰动，实现压缩、拉伸和剪切3个应力状态；α表征粒料的正交异性程度，并减少正交异性增量本构方程中的未知数；Uzan三参数应力依赖模型表征模量和泊松比的应力依赖性。推导了增量本构方程，并计算了粒料的5个回弹特性参数：竖向模量、水平向模量、竖平面内泊松比、水平面内泊松比，剪切模量。使用该方案对3种粒料（石灰岩、砾石、花岗岩）进行了室内试验研究，计算了粒料的回弹特性参数，分析了应力水平、级配和含水率对动态回弹特性的影响。结果表明：①该解决方案同时考虑了粒料的正交异性和应力依赖性，实测数据和计算数据相关性良好，计算结果准确合理；②粒料的回弹模量和泊松比都具有应力依赖性，动态回弹模量主要受体应力的影响，泊松比受剪切应力的影响更大；③粒料的回弹模量和泊松比均存在显著的正交异性，当剪应力较大时，有可能出现剪胀现象；④各回弹特性参数随影响因素的变化规律正确，该方案能够显著地反映出各因素对回弹特性参数的影响。

Research on Cross-anisotropic Nonlinear Resilient Characteristics of Granular Material

The resilient behavior of granular material is nonlinear and cross-anisotropic. A solution accounting for both stress-dependency and cross-anisotropy of the resilient characteristic has been proposed. The solution consists of three parts: an improved repeated load triaxial test (RLTT) program, a cross-anisotropic parameter α, and an Uzan stress-dependent model. The improved RLTT contains several stress levels. By applying stress disturbance at each level, three stress states were achieved: compressive, tensile and shear stress states. α is a measure of anisotropy. It reduces the number of unknowns in the cross-anisotropic incremental constitutive model. The Uzan three-parameter model can characterize the stress dependency of resilient moduli and Poisson's ratio. The incremental constitutive equations were derived, and five resilient parameters, including the vertical modulus, horizontal modulus, vertical-horizontal Poisson's ratio, horizontal-horizontal Poisson's ratio, and the shear modulus, were obtained. Three granular materials (limestone, gravel, and granite) were tested using the aforementioned solution. The resilient parameters were determined, and the influence of stress levels, gradation, and moisture content was analyzed. The main findings are as follows: ① The solution considering both stress-dependency and cross-anisotropy works accurately and robustly. The calculated strains have high correlation with the measured strains. ② Both the resilient modulus and Poisson's ratio are stress-dependent. While the dynamic resilient modulus is dependent mainly on the bulk stress, the Poisson's ratio is more influenced by the octahedral shear stress. ③ Resilient modulus and Poisson's ratio demonstrate significant cross anisotropy. High shear stress may lead to dilation. ④ The effects of the influencing factors on resilient characteristic parameters are correctly and significantly reflected in the solution proposed.