Characterization of soil behaviour for earthquake engineering applications

目前的地震设计方法主要依靠经验数据来评估液化危害，总体上比较保守。因此，在地震期间防范可能出现的生命线故障的努力往往会导致巨大的经济成本。更好地了解土壤在实际的原位加载路径和排水条件下的行为对于正确表征地震过程中土壤的反应是必不可少的。它将能够制定全面的模型，从而可靠地预测土工结构在施加载荷下的反应。******对土壤行为的基本理解主要来自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，地应力路径将由这三个主应力的变化所决定，而变形总是伴随着孔隙体积和孔隙压力的同时变化。虽然排水和不排水近似可能在特定情况下产生足够的精度，但在一些情况下，这种近似不会产生令人满意的结果。******对液化现象的深入了解通常是通过模拟体波（通常是垂直传播的s波）的传播而得到的。但是，由于表面波载荷的作用，导致了大量的液化失效。目前，对于目前的理解是否适用于由表面波（如瑞利波）或组合体波（同时发生的p波和s波）引起的液化，几乎一无所知。该研究首次尝试使用空心圆柱扭转剪切（HCT）装置模拟瑞利波（或同时p-和s-波）引起的应力条件。这是实验研究中的一条全新的探究线，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响应的实验室之一。******提出的三维加载路径对勒达粘土影响的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未受干扰的Leda粘土试样（使用Laval取样器获得）进行一次HCT测试，最多可进行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，在准备HCT试样的同时保留内芯进行三轴和/或简单剪切试验。******提高对环境因素对土壤行为的影响的了解，对于在北方进行资源开发和处理与全球变暖和可持续发展有关的问题是必不可少的。考虑孔隙体积和压力同时变化的位点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、矿山尾矿和水电站大坝的安全

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.**