Development of Element tests for elucidating mechanical behavior of granular materials subjected to cyclic moving loads

本研究探讨粒状材料在循环移动荷载作用下的力学行为，例如碎石路基和铁路道碴，并提出了一种新的测试方法和新的分析程序，以研究主应力轴旋转对粒状材料循环塑性变形的影响。得出以下结论：1.在其他试验条件相同的情况下，移动加载试验得到的循环塑性变形远大于固定加载试验得到的循环塑性变形。2.在偏应力幅恒定、围压恒定的条件下，通过动载试验得到的残余应变与动载试验中由力-位移关系计算得到的宏观残余应变相比很小，而动载试验得到的残余应变与动载试验中由力-位移关系计算得到的宏观残余应变相比很小 ...更多信息 采用新研制的“多环剪切仪”进行的循环扭转单剪试验与移动荷载试验基本相当。因此，多环剪切试验适合于模拟交通荷载作用下下部结构内部实际应力状态的单元试验。此外，主应力轴的旋转对散体材料的循环变形特性有显著影响。3.提出了两种模拟散体材料在循环移动荷载作用下力学行为的分析方法。一种是线弹性有限元分析，考虑了散粒体材料的单元试验累积应变的材料特性，可以粗略估算循环荷载作用下散粒体下部结构的残余沉降量;另一种是不连续分析，它的单元形状很好地模拟了真实的颗粒的形状，因为在不连续分析中，单元形状是决定颗粒集合体力学行为的主要因素之一。少

This study examines the mechanical behavior of granular materials subjected to cyclic moving loads, for example gravel roadbed and railroad ballast, and both a new testing method and new analytical procedures to examine the effects of the rotation of principal stress axes on cyclic plastic deformation of granular materials are proposed. The following conclusions can be obtained ;1.Cyclic plastic deformation obtained through moving loading tests is much larger than those obtained through fixed-place cyclic loading tests when other experimental conditions are the same. Accordingly, the difference in loading methods has a significant influence on the cyclic plastic deformation of granular materials.2.Residual strain obtained through cyclic loading triaxial tests with constant amplitude of deviator stress while controlling confining pressure constant is very small compared with the macro residual strain calculated from force-displacement relationships in moving loading tests, while that of … More cyclic torsional simple shear tests using a newly developed "Multi-ring shear apparatus" is almost equivalent to moving loading tests. Therefore, the multi-ring shear test is appropriate for an element test to simulate the actual stress states inside substructures under traffic loads. Moreover, it was revealed that the rotation of principal stress axes has a significant effect on cyclic deformation characteristics of granular materials.3.Two analytical procedures for simulating the mechanical behavior of granular materials subjected to cyclic moving loads were proposed. One is linear elastic FE analysis considering the material properties of cumulative strain derived from element test results of granular materials, which can roughly estimate the residual settlement of granular substructures due to cyclic loading. The other is discontinuous analysis which elements imitate the shape of real gram particles well because it was revealed that the element shape is one of the dominant factors to determine the mechanical behavior of granular assemblage in discontinuous analysis. Less