循环荷载下结构性黏土的动力响应特征及主应力轴旋转效应

Considering the mechanical characteristics of structured clay and evaluation of structural damage under long-term cyclic loading, by the means of macro-micro test combined with theory analysis, dynamic response for different structured clay of cyclic loading on principal stress axes rotation and principal stress axes orientation are conducted, while the latter one including stress paths of constant confining pressure and variable confining pressure, the difference of dynamic response characteristics under different stress paths can be obtained, with the evolution of microstructures as well as the variations of mechanical properties of structured clay, then the evolution mechanism of deformation and strength of structured clay under cyclic loading is revealed. Based on the above, the effects of principal stress axes rotation on the deformation, pore pressure and strength of structured clay are explored, the damage regularity of structured clay subjected to dynamic disturbance and its quantitative evaluation are proposed. A simplified method for calculating the cumulative deformation of structured clay with cyclic rotation of principal stress axes will be established, which can provide scientific basis and technical support for construction on areas of structured clay in China.

本项目以深化认知长期循环荷载作用下结构性黏土的动力特性与结构损伤的工程后效评价为主线，采用宏观、微观试验与理论分析相结合的手段，针对不同强弱结构性黏土开展主应力轴定向循环加载（常围压应力路径、变围压应力路径）、主应力轴旋转的循环加载路径下的动力学响应试验，研究不同应力路径下结构性黏土力学性状的差异性响应，通过微观结构演变性状分析结构性黏土力学性状变化的物理机制，揭示工程建设中结构性黏土在循环荷载作用下的变形规律与强度演化机理。在此基础上，分析主应力轴循环旋转对结构性黏土变形、孔压及强度的影响，提出结构性黏土受动力扰动后的损伤规律及其力学特性的定量评价方法，进而建立考虑主应力轴循环旋转的结构性黏土累积变形的简化计算方法，为我国结构性黏土地区基础建设提供科学的设计依据和技术支撑。

本项目以结构性黏土为研究对象，采用宏观、微观试验与理论分析相结合的手段，研究了不同应力路径下结构性黏土力学特性的应力路径依赖性，探讨不同卸荷路径及卸荷速率对应力-应变关系、孔压变化规律及破坏强度特性的影响；揭示小应变条件下结构性黏土的动剪切模量随围压水平演化规律，探讨考虑土体结构性损伤影响的动剪切模量表征方法，阐述结构性损伤对动剪切模量影响的物理机制；基于剪切模量的劣化定量评价结构性黏土剪切过程中的结构损伤，建立了变形发展的损伤参数演化规律；针对不同强弱结构性黏土开展不同循环加载路径下的动力学响应试验，研究复杂应力路径下结构性黏土力学性状的差异性响应，揭示工程建设中结构性黏土在循环荷载作用下的变形规律与强度演化机理；建立长期循环荷载作用下结构性黏土的累积变形简化计算方法，为长期循环荷载下结构性黏土地基动力附加沉降的预测提供科学的设计依据。本项目获取了长期循环荷载作用下结构性黏土的动力特性与结构损伤的工程后效评价，为合理利用黏土的结构性潜能提供技术支撑，研究成果为我国结构性黏土地区基础建设提供科学的理论依据和技术支撑，有深远的现实意义。