Research Initiation: Experimental Investigation and Constitutive Modeling of Cohesionless Soil Under Cyclic Loading

在涉及土壤的工程设计中，最常见的问题可能是计算一般应力状态对土壤产生的运动的问题。直到最近十到二十年，计算由小荷载引起的非常小的运动（与导致倒塌的荷载相比）是可行的，或者计算倒塌荷载并假设运动非常大以至于没有必要计算它们。对于两种极端都无效的常见情况，有必要应用“工程判断”。随着现代数字计算机的出现，研究人员对这类问题进行了双管齐下的研究。一种模式涉及尝试测量广义土壤特性（响应于广义施加应力状态的完全应变状态）和开发描述土壤响应的模型。第二种模式涉及数值方法的发展，因此所得的土壤性质可以用来预测现场的质量运动。这个建议涉及第一种模式。本研究的目标是对洁净砂样品对复杂应力状态的响应进行可靠的测量，然后拟合适当的模型，以便对所得特性进行分析描述。所谓的空心圆筒装置将用于测量性能。将尝试各种本构模型。单调加载（直接加载到破坏）和循环加载（反复施加小于破坏应力的应力）都将被使用。

Perhaps the most common problem in engineering design involving soils, is the problem of calculating the movements that result from application of general states of stress to the soils. Until the last ten to twenty years, it was feasible to calculate either the very small movements that resulted from small loads (compared to the load that causes collapse), or to calculate collapse loads and assume that movements were so large that it became unnecess- ary to calculate them. For common cases in which neither extreme was valid, it was necessary to apply "engineering judgement." With the advent of modern digital computers, researchers are engaged in a two-pronged attack on this class of problem. One mode involves attempts to measure generalized soil properties (complete state of strain in response to a generalized state of applied stress) and development of models to describe the soil response. The second mode involves development of numerical methods so the resulting soil properties can be used to predict mass movements in the field. This proposal involves the first mode. The goal of this research is to perform reliable measurements of the response of samples of clean sands to complex states of stress, and then to fit appropriate models to allow analytic description of the resulting properties. The socalled hollow-cylinder device will be used to measure properties. A variety of constitutive models will be tried. Both monotonic loading (load directly to failure) and cyclic loading (repeated application of stresses less than the failure stresses) will be used.