Direct Measurement of Strain-Rate Dependent Constitutive Relations for the Compression of Clay

CMS-9622644标题：《粘土压缩应变率依赖本构关系的直接测量》合著者：普渡大学土木工程系Gerald A.Leonards和Patrick J.Fox拟议研究计划的目标是提供明确的实验数据，以解决粘土固结过程中长期存在的应变率效应问题。新的实验技术将被应用于在固结过程完成期间和之后测量与时间相关和与时间无关的压缩性分量，而不需要对测试结果进行分析解释。已知对应变率效应敏感的原状土将使用以下两种方法进行测试：1)专门处理低侧壁摩擦的固定环固结计，2)使用流量泵体积控制系统，改装成在零侧摩擦条件下提供基本上一维应变的Ko三轴固结仪。将直接测量孔隙率和有效应力的局部值。通过测试不同厚度的样品，可以研究大范围的应变率。多余的实验将被用来确定结果是没有偏差的，因为在一种情况下，由于偏离零侧向摩擦的微小偏差，而在另一种情况下，没有横向应变的偏差。利用直接测量得到的基本本构关系，对增量加载试验中孔压消散和恒应变速率(CRS)试验中孔压恢复的预测，将与使用块状试件复制试件的预测进行比较。这项研究的结果将对如何教授巩固概念以及如何在实践中应用这些概念产生根本性的影响。

CMS-9622644 Title: "Direct Measurement of Strain-Rate Dependent Constitutive Relations for the Compression of Clay" co-PI's: Gerald A. Leonards and Patrick J. Fox, Department of Civil Engineering, Purdue University The objective of the proposed research program is to provide definitive experimental data to resolve long-standing issues of strain rate effects during the process of consolidation in clay. Novel experimental techniques will be applied to measure the time-dependent and time- independent components of compressibility both during and after the consolidation process is completed, without the need for analytical interpretation of the test results. Undisturbed soils, known to be sensitive to strain rate effects, will be tested using: 1) a fixed-ring consolidometer specially treated for low sidewall friction, and 2) a Ko-triaxial cell modified to provide essentially one-dimensional strain under conditions of zero side friction, using a flow-pump volume control system. Local values of void ratio and effective stress will be measured directly. Large ranges in strain rate will be investigated by testing samples of different thickness. Redundant experiments will be used to establish that the results are free from bias due to minor departures from zero side friction in one case, and from zero lateral strain in the other. With the basic constitutive relations obtained from direct measurement, predictions of pore water pressure dissipation in incremental loading tests, and build up of pore water pressures in constant rate of strain (CRS) tests, will be compared with those using replicate specimens from block samples. The results of this study will have a fundamental bearing on how consolidation concepts are taught, and on how they are applied in practice.