Study on Elucidation and Prediction of Mechanical Behavior of Saturated/Unsaturated Granular Base Subjected to Cyclic Moving Loads.

本文研究了饱和和非饱和条件下循环移动荷载作用下粒状材料的力学行为，如砾石路基和铁路道碴，并提出了一种新的试验方法和新的分析程序，以研究主应力轴旋转和含水量对粒状基层材料循环塑性变形的影响。可以得出以下结论：1。采用固定荷载法和移动荷载法对基层材料进行了风干和饱和两种状态下的小比例模型试验。研究结果表明，基层材料含水量对粒料基层的力学行为有很大影响，采用移动荷载时，对循环荷载作用下粒料基层残余沉降发展的影响显著.两种类型的多环剪切试验，可以考虑主应力方向的变化，如交通荷载，以同样的方式加载方法在小比例尺模型试验。结果表明，饱和后土体的抗剪强度降低，累积残余应变增加，且无论加载方式和含水量如何，多环剪切试验的力学行为与小比例模型试验的力学行为非常相似.根据粒料基层材料的强度和变形特性，提出了一种估算粒料基层在车轮反复行驶作用下循环塑性变形的新方法。根据基层材料的多环剪切试验结果，采用线弹性有限元分析的简单分析方法，可以粗略估算循环荷载作用下饱和和非饱和条件下粒料基层的残余沉降。

This study examines the mechanical behavior of granular materials under saturated and unsaturated conditions subjected to cyclic moving loads, for example gravel roadbed and railroad ballast, and both a new testing methods and new analytical procedure to examine the effects of the rotation of principal stress axes and water content on cyclic plastic deformation of granular base course materials are proposed. The following conclusions can be obtained;1. Two types of small scale model tests which adopted a fixed-place loading method and a moving loading method were performed with a base course material under air-dried condition and saturated condition. As the results, it was revealed that the water content of the base course material influences the mechanical behavior of granular base strongly, and the effect on the development of residual settlement for granular base under cyclic loading remarkably comes to the surface in employing moving loads.2. Two types of multi-ring shear tests, which can consider a change in direction of principal stresses like traffic loads, were performed in the same way as loading methods in small scale model tests. As the results, it was revealed that the shear strength decreased and the cumulative residual strain increased due to the saturation, and that the mechanical behavior in multi-ring shear tests is very similar to that in small scale model tests, regardless of loading methods and water contents.3. A new method to estimate cyclic plastic deformation of granular base under repeated wheel traveling in terms of the strength and deformation characteristics of granular base course materials was proposed. The simple analytical procedure with linear elastic FE analysis considering the cumulative strain derived from multi-ring shear test results of base course materials can roughly estimate the residual settlement of granular base under saturated and unsaturated conditions subjected to cyclic moving loads.