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

本研究考察了颗粒状材料在饱和和非饱和条件下在循环移动荷载作用下的力学行为，例如砾石路基和铁路道砟，并提出了一种新的测试方法和新的分析方法来研究主应力轴旋转和含水量对颗粒状基层材料循环塑性变形的影响。可以得到以下结论：1。采用固定加载法和移动加载法对基层材料在风干和饱和条件下进行了两种小比例尺模型试验。结果表明，基层材料含水量对颗粒基的力学行为有强烈的影响，循环荷载作用下对颗粒基残余沉降发展的影响在移动荷载作用下明显地表显现出来。采用与小比例尺模型试验中的加载方法相同的方法进行了两种多环剪切试验，这些试验可以像交通荷载一样考虑主应力方向的变化。结果表明，饱和作用使土体抗剪强度降低，累积残余应变增大，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尺度模型试验非常相似。从颗粒基层材料的强度和变形特性出发，提出了一种估算轮重复运动下颗粒基层循环塑性变形的新方法。考虑基层材料多环剪切试验结果的累积应变，采用线弹性有限元分析的简单解析方法，可以大致估算出循环移动荷载作用下颗粒基层在饱和和非饱和条件下的残余沉降。

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.