Unique Relationship Between Small Strain Shear Modulus and Effective Stresses at Failure for Dilative Soils

膨胀土小应变剪切模量与失效有效应力之间的独特关系

• 批准号: 1031135
• 负责人: Christopher Baxter
• 金额: $ 7.71万
• 依托单位: University of Rhode Island
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1031135&HistoricalAwards=false
• 关键词: Unique; Relationship; Between; Small; Strain

This grant provides funding to investigate whether a unique relationship exists between small strain shear modulus and effective stresses at failure during triaxial compression for dilatant soils. This hypothesis was developed based on preliminary tests involving isotropically consolidated drained triaxial compression tests on an artificially cemented silty sand with shear wave velocity measurements made throughout shearing. There were two important findings from these tests: 1.) the ratio of small strain shear modulus to principal effective stress at failure was constant for the given soil, independent of the degree of cementation, density, and consolidation stress; and 2.) there was a clear trend of the small strain shear modulus increasing during shear to a maximum value and then decreasing despite continued increases in the deviator stress up to failure. To test this hypothesis, Ko-consolidated drained triaxial compression tests will be performed on three different soils in a dilative state: coarse, angular sand, non-plastic silt, and high plasticity clay. Shear wave velocity measurements will be made throughout the consolidation and shear phases of each test. If these findings are representative of dilatant or structured soils in general, then there are several important implications for engineering practice. A significant application of this concept would be the estimation of effective stress strength parameters directly from in situ shear wave velocity measurements in soils that have been traditionally problematic to sample and test in the laboratory, such as dense sands and silts or sensitive clays. Establishment of the proposed relationship would potentially change how geotechnical site investigations and laboratory testing program are designed. Another application would be that in situ shear wave velocity measurements, for example from cross-hole or seismic cone penetration tests, could be used as an early warning system for the onset of failure in cemented, structured, or sensitive soils during staged construction of embankments and natural slopes which fail progressively.

该赠款提供了资金，以研究小应变剪切模量和在三轴压缩期间的有效应力之间是否存在独特的关系。该假设是基于涉及在人工胶结的粉质砂上的初步测试，该测试涉及各向同性的排水三轴压缩测试，并在整个剪切过程中进行了剪切波速度测量值。这些测试中有两个重要的发现：1。）小应变剪切模量与给定土壤的原理有效应力的比率是恒定的，而与胶结，密度和固结应力无关；和2.）剪切期间小应变剪切模量增加到最大值的趋势明显趋势，然后尽管驱动器压力持续增加到失败，然后减少了。为了检验这一假设，将在稀疏状态下在三种不同的土壤上进行KO固结的排水三轴压缩测试：粗砂，非塑料粉和高可塑性粘土。剪切波速度测量将在每个测试的整个巩固和剪切阶段进行。 如果这些发现总体上代表了膨胀或结构化土壤，那么对工程实践会有一些重要的影响。该概念的一个重要应用将是直接从原位剪切波速度测量的土壤中估算有效的应力强度参数，这些土壤传统上对实验室中的采样和测试是有问题的，例如密集的沙子和砂浆或敏感的粘土。建立拟议的关系将有可能改变岩土现场调查和实验室测试计划的设计。另一个应用是，原位剪切波速度测量值，例如，通过交叉孔或地震锥渗透测试，可以用作预警系统，用于在分阶段结构的横向结构和自然斜率逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐渐逐步的警告系统。