循环荷载作用下粗颗粒基床填料累积变形演化状态特征及判别准则

It is one of the key technical problems that how to effectively control the cumulative deformation of subgrade under the long-term cyclic loading by train in the railway construction, especially for high-speed railway. Controlling the evolution state of long-term cumulative deformation in the design is an effective solution to the engineering problem, but the key in this method is determination the state controlling parameters of subgrade filling. This program begins with the assumption that the rate of cumulative deformation is closed to power-law distribution under cyclic loading, and then based on the cyclic loading triaxial test data to demonstrate the hypothesis. Next, the criterion will be established based on the cumulative deformation convergence or not and whether the speed of convergence is fast or slow, which is expressed by the negative power function and the value of power exponent. The test method will put forward to determine the threshold of the cumulative deformation state. The validity and rationality of the criterion and the threshold are examined by the large-scale model test. The threshold of cumulative deformation state will be obtained for different gradation composition coarse filling which can be differentiate by the fractal dimension of particle size, and then the design controlling index of subgrade filling will be suggested, which expressed by “double power exponent”, based on the relation between the fractal dimension of particle size and he threshold of the cumulative deformation state. The research results lay foundation for the functionality requires of durability of subgrade from conceptual design to quantitative analysis.

如何有效控制由粗颗粒土工填料构筑的基床结构在长期列车循环荷载作用下的累积变形是铁路建造的技术难点之一，对于高速铁路这一问题更尤为突出。基于长期累积变形演化状态控制进行基床结构设计是解决这一工程问题的有效途径，而基床填料变形状态控制参数的合理确定是该方法的关键所在。项目以循环加载条件下累积变形速率符合幂律分布假定为出发点，以室内循环加载三轴试验所得数据为基础进行推理论证。继而，建立以负幂函数表达、幂指数表征的累积变形演化状态收敛、与发散快慢的数学判别准则，提出确定累积变形演化状态阈值参数的试验方法；判别准则及阈值参数的合理性通过大尺寸模型试验进行分析验证；以粒径分维数表征不同颗粒级配组成的粗颗粒填料，通过试验确定其累积变形演化状态阈值参数，分析粒径分维数与状态阈值参数之间的关系，建立以“双幂指数”表征的填料设计控制指标。研究成果可为基床结构考虑耐久性功能要求从概念设计向定量分析发展奠定基础。

如何有效控制由粗颗粒土工填料构筑的基床结构在长期列车循环荷载作用下的累积变形是铁路建造的技术难点之一，对于高速铁路这一问题更尤为突出。基于长期累积变形演化状态控制进行基床结构设计是解决这一工程问题的有效途径，而基床填料变形状态控制参数的合理确定是该方法的关键所在。项目针对广泛用于铁路基床构筑的级配碎石粗颗粒填料，采用经改造的动三轴试验系统，开展了总计约千万次的循环加载三轴试验，获得了近百条不同应力条件下的累积变形曲线，分析了累积变形速率随荷载作用次数的演化变化规律，论证了循环加载下累积变形速率符合负幂律演化规律；建立了以负幂函数表达、幂指数表征的累积变形演化状态收敛、与发散快慢的数学判别准则，提出了幂指数P=0、1、2可作为区分快速稳定、缓慢稳定、缓慢破坏四个状态的幂次阈值；通过构筑模型试验，验证了循环加载条件下累积演化状态分类及其状态阈值的合理性。建立的状态阈值判别准则、状态阈值参数在高速铁路路基基床结构设计、重载铁路基床结构设计中得到了应用；提出的累积变形演化状态分析方法及其阈值参数确定的试验方法成功延伸至静载下土工材料长期变形的演化规律分析。项目研究成果为铁路基床结构设计以及铁路路基长期变形的控制提供了理论支撑，研究成果直接服务于工程建设。