Collapse, Steady State Concept, and Liquefaction of Granular Soils

这项研究计划解决的基本概念，以了解颗粒材料(通常是沙)饱和水(地下水位以下)，受到强烈的地面运动时，地震震动的行为。在这种情况下，这种土有可能发生液化，即失去抗剪强度并发生较大变形，从而破坏建筑物基础。在这种液化土壤上修建或通过的隧道和管道。这种现象与饱和松散砂体的反应有关，这些松散砂体受到足够的应变，从而导致了水流滑移。毁灭性的山体滑坡就是这种流动滑坡的一个例子。稳态(流动滑动)和周期(地震)行为之间的关系正在通过基础实验研究来解决。需要研究的一个关键因素是砂布结构坍塌的概念。“坍塌”的概念与收缩砂岩的结构是亚稳定的这一事实有关。在塌陷的骨架中，小的剪切应变可能足以产生颗粒的突然重新排列，并伴随着相邻颗粒之间接触点的损失，随之而来的是孔隙水压力的大幅增加。因此，砂土的抗剪强度降低到一个较小的值，并且砂土很容易发生大变形。这项调查的结果有望有助于更好地理解液化现象和相关的不稳定性，并提高预测其发生的能力。

This research program addresses fundamental concepts for understanding the behavior of granular material (usually sand) saturated with water (below the ground water table) when subjected to the strong ground motions resulting from earthquake shaking. Under these conditions, such soils have the potential to "liquefy", that is to lose shear strength and undergo large deformations, resulting in damage to building foundations, tunnels and pipelines built on or passing through such liquefied soil. This phenomenon is related to the response of saturated loose sands strained sufficiently to result in flow slides. A devastating landslides is an example of such a flowslide. The relation between the steady state (flow slide) and the cyclic (earthquake) behavior is being addressed by fundamental experimental studies. A key element to be investigated is the concept of structural collapse of the sand fabric. The concept of "collapse" is associated with the fact that the structure of contractive sands is metastable. In a collapsive skeleton, small shear strains may be sufficient to produce a sudden rearrangement of grains with an associated loss of contact points between neighboring grains, accompanied by a large increase in pore water pressure. Consequently, the shear strength of the sand is reduced to a small value and the sand becomes susceptible to large deformations. The results of this investigation are expected to contribute to an improved understanding of liquefaction phenomena and associated instabilities, and to result in an improved ability to predict their occurrence.