Characterization of soil behaviour for earthquake engineering applications

地震工程应用中的土壤行为表征

• 批准号: RGPIN-2018-05334
• 负责人: Sivathayalan, Siva
• 金额: $ 1.89万
• 依托单位: Carleton University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=713594
• 关键词: Characterization; soil; behaviour; earthquake; engineering

Current seismic design approach is generally conservative as it relies primarily on empirical data to assess the liquefaction hazard. As a result, attempts to safeguard against possible lifeline failures during earthquakes often result in huge economic costs. Better understanding of the behavior of soils under actual in-situ loading paths and drainage conditions is essential to properly characterize the response of soils during earthquakes. It will enable the formulation of comprehensive models that will lead to reliable predictions of the response of the geotechnical structures under imposed loads. Fundamental understanding of soil behavior has mainly been derived from laboratory tests under fully drained or fully undrained conditions along specific stress paths. In reality, in-situ stress paths would be dictated by variations in all three principal stresses, and deformation would invariably involve simultaneous changes in pore-volume and pore-pressure. While drained and undrained approximations might yield sufficient accuracy under specific situations, there are several instances during which such approximations will not yield satisfactory results. Insights into the liquefaction phenomena have generally been elicited by simulating the propagation of body waves (often a vertically propagating s-wave). But, a large number of liquefaction failures occur due to surface-wave loading. At present virtually nothing is known about whether current understanding applies to liquefaction due to surface waves (e.g., Rayleigh wave) or combined body waves (simultaneous p- and s-waves). The proposed research is the first ever attempt to simulate the stress conditions due to Rayleigh (or simultaneous p- and s-) waves using a hollow cylinder torsional shear (HCT) device. This is a completely new line of inquiry in experimental research and our laboratory is one of the very few in the world that can explore the response of soils along such complex stress paths. Proposed research on the effects of 3D loading paths on Leda clay also contains several novel and innovative elements. The new HCT sample trimmer will allow using a given high-quality undisturbed Leda clay specimen (obtained using the Laval sampler) for one HCT test, and up to 12 triaxial or 8 simple shear tests (or a combination of the two). This is the first such attempt ever where an HCT specimen is prepared while preserving the inner core for triaxial and/or simple shear tests. Improved understanding of the effects of environmental factors on soil behavior is essential to pursue resource development in the north, and to address concerns related to global warming and sustainable development. Site characterization methods that consider simultaneous changes in pore volume and pressure will yield more meaningful results. The outcome of the proposed research will directly contribute to the safety of infrastructure, mine tailings and hydro dams.

目前的抗震设计方法通常是保守的，因为它主要依赖于经验数据来评估液化危害。因此，在地震期间防止可能的生命线故障的尝试往往导致巨大的经济成本。更好地了解土壤在实际原位加载路径和排水条件下的行为对于正确描述地震期间土壤的反应至关重要。它将使制定全面的模型，这将导致可靠的预测的岩土结构的反应下施加的负载。 对土壤特性的基本认识主要来自于沿着特定应力路径在完全排水或完全不排水条件下的实验室试验。实际上，原地应力路径将由所有三个主应力的变化决定，并且变形将总是涉及孔隙体积和孔隙压力的同时变化。虽然排水和不排水近似在特定情况下可能会产生足够的精度，但在某些情况下，这种近似不会产生令人满意的结果。 对液化现象的认识通常是通过模拟体波（通常是垂直传播的s波）的传播来得出的。但是，大量的液化破坏是由于表面波荷载引起的。目前实际上还不知道目前的理解是否适用于由于表面波引起的液化（例如，瑞利波）或组合体波（同时的p波和s波）。拟议的研究是有史以来第一次尝试模拟应力条件下，由于瑞利波（或同时p和s）波使用空心圆柱体扭转剪切（HCT）设备。这是一个全新的实验研究领域，我们的实验室是世界上极少数能够探索土壤沿着如此复杂的应力路径的反应的实验室之一。 拟议的三维加载路径对勒达粘土的影响研究也包含了一些新颖和创新的元素。新的HCT样品修剪器将允许使用给定的高质量原状Leda粘土试样（使用拉瓦尔采样器获得）进行一次HCT测试，以及多达12次三轴或8次简单剪切测试（或两者的组合）。这是有史以来第一次这样的尝试，其中HCT试样制备，同时保留三轴和/或简单剪切试验的内核。 更好地了解环境因素对土壤行为的影响，对于北方的资源开发以及解决与全球变暖和可持续发展有关的问题至关重要。考虑孔隙体积和压力同时变化的场地表征方法将产生更有意义的结果。拟议研究的结果将直接有助于基础设施、尾矿和水坝的安全。