Micromechanical model for shear band formation in granular soils and its application to bearing capacity problems

土工可能会承认，剪切带的出现是土体破坏时最显著的现象之一。本研究的目的是对颗粒土进行数值和物理试验，并在此基础上提出一种新的剪切带形成的细观力学模型。这项研究尚未完成，但迄今为止已经完成了一些有趣的观察结果，这些观察结果似乎对剪切带的动态解释很重要，总结如下：1.研究了三个剪切带，其中两个来自天然土壤，另一个来自人工组装的光弹棒，其中特别感兴趣的是剪切变形引起的微观组构。柱状加载路径的发展及其旋转崩塌是颗粒土细观力学中需要考虑的最重要的观测。由此得出结论，偶应力在剪切带的形成中起着重要的作用。使用Cundall和Strack(1979)开发的Ball进行了数值模型试验，以确定在物理试验中观察到的织物发展是否可以在这样的数值模拟中重现。结果有力地表明，数值模拟为研究剪切带的形成提供了一个非常有用的工具。

Soil engineers may admit that occurrence of shear bands is one of the most dramatic phenomena in soil bodies at failure. The purpose of the present study is to do some numerical and physical tests on granular soils, and also, based on these results, to suggest a new micromechanical model of shear band formation. The study has not been completed yet, but some interesting observations, which seem important in the dynamic interpretation of shear bands, have been done so far, as summarized below:1. Three shear bands, two from natural soils and the other from an artificial assembly of photoelastic rods, were studied with special interest in their micro-fabric induced by shearing deformation. Development of column-like load paths and their collapse by rotation are most important observations to be taken into account in micromechanics of granular soils. It is concluded from these findings that couple-stress can play an important part in the formation of shear bands.2. Numerical model tests using BALL developed by Cundall and Strack (1979) have been carried out to see if the fabric development observed in the physical tests can be reproduced in such numerical simulations. The result strongly suggests that the numerical simulation provides a very useful tool for studying shear band formation.