Understanding of progressive failure in view of particle crushing and it's modelling

本研究包括两个部分；实验和分析。得到了以下结果：实验研究包括：1.单颗粒压缩试验；2 .一维压缩试验；可破碎模型地面的加载试验。一系列单颗粒试验表明，试件存在三种破坏模式；分裂破坏，剪切破坏和压缩破坏，取决于接触点的数量和它们的接触力的相对大小。从一维压缩试验中观察到，所谓的预固结压力对应于累积破碎比的50%，在预固结压力下，随时间变化的沉降速率最大，并且对特定类型的可破碎材料也会出现跳跃现象。加载试验结果表明，随着承载安全系数的减小，颗粒的时间依赖性更加明显，颗粒的旋转自由度对破碎颗粒的数量和破碎区域起着重要的决定作用。DEM分析是通过合并每个粒子内部有许多子粒子来进行的。用单颗粒试验结果标定模型参数，可以较好地模拟其一维行为。但时间依赖行为没有得到充分的模拟，表明该模型需要一个参数来描述时间依赖行为。

This research consists of two parts; experimental and analytical. The following results were obtained. The experimental research includes 1.compression tests on a single particle, 2. One-dimensional compression tests, and 3. Loading tests on crushable model ground. A series of single particle tests revealed that there are three types of failure mode; split failure, shear failure and compressive failure, depending on the number of contact points and the relative magnitude of their contact forces. From the one- dimensional compression tests, it was observed that so-called pre-consolidation pressure is corresponding to 50 % of accumulated crushing ratio and the rate of time dependent settlement behavior become the largest at the pre-consolidation pressure, and also some jumping phenomena occur for a particular type of crushable materials. It was found from the loading tests that the time dependent behavior becomes more marked as the factor of safety for bearing capacity decreases, and the freedom of particle rotation plays an important role in determining the number of crushing particles and the zone of the crushing. DEM analysis was conducted by incorporating each particle having a number of its baby particle inside. The one-dimensional behavior was reasonably simulated if the model parameters were calibrated by the single particle test results. But the time dependent behavior was not fully simulated, suggesting that the model needs a parameter describing time dependent behavior.