Characterization of soil behaviour for earthquake engineering applications

对土壤特性的基本认识主要来自完全排水或完全不排水条件下的实验室试验，以及沿着特定应力路径的试验。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值可能适用于取决于土壤渗透性和加载速率的特定情况，但在某些情况下，这种近似值不会产生令人满意的结果。（土壤）不稳定的后果可能是灾难性的，试图防止生命线故障和减轻地震中的损害往往会导致巨大的经济成本。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。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成功描述地震期间土体的反应至关重要。这样的理解将使制定全面的模型，将导致可靠的预测的岩土结构的响应下施加的负载。更好地了解环境因素对土壤行为的影响，对于在北方进行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尾矿和水坝的安全，并使全国各地有问题的土壤的设计充满信心。建议的研究的目标是评估初始状态的影响，广义应力路径，和局部排水的静态和地震反应的土壤。一个系统的研究，隔离，并探讨这些变量中的每一个将进行剪切-体积耦合变形的本构关系的影响，和液化敏感性提供一个基本的理解。将使用三轴、简单剪切和空心圆柱体试验评估广义初始应力条件、应力路径和排水程度对土壤应力-应变行为及其不稳定特性的影响。此外，颗粒形状，过固结，和冻融循环对土壤的机械性能的影响将进行评估。更好地了解这些影响将使数值工具，以自信地描述预期的字段行为。将在荷载和位移控制荷载模式下进行单调和循环试验，以适当模拟预期的现场荷载。液化的触发将被认为不仅是不排水荷载的结果，而且在部分排水条件下和涉及膨胀排水的情况下。

Fundamental understanding of soil behaviour has mainly been derived from laboratory tests under fully drained or fully undrained conditions, and 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 be applicable to specific situations depending on the permeability of the soil and the loading rate, there are several instances during which such approximations will not yield satisfactory results. Consequences of instability (in soils) can be catastrophic, and attempts to safeguard against lifeline failures and to mitigate damage in the event of earthquakes often result in huge economic costs. Current seismic design approach is generally conservative as it relies primarily on empirical data to assess the liquefaction hazard. Better understanding of the behaviour of soils under actual in-situ loading paths and drainage conditions is essential to successfully characterize the response of soil masses during earthquakes. Such an understanding will enable the formulation of comprehensive models that will lead to reliable predictions of the response of the geotechnical structures under imposed loads. Better understanding of the effects of environmental factors on soil behaviour 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 mine tailings, and hydro dams, and enable confident designs in problematic soils across the country. The objectives of the proposed research are to assess the effects of initial state, the generalised stress path, and partial drainage on the static and seismic response of soils. A systematic study that isolates, and explores each of these variables will be undertaken to provide a fundamental understanding of the effects shear-volume coupled deformation on the constitutive relations, and liquefaction susceptibility. The effect of generalised initial stress conditions, stress path, and the degree of drainage on the stress-strain behaviour of soils and their instability characteristics will be assessed using triaxial, simple shear, and hollow cylinder tests. In addition, the effects of particle shape, over consolidation, and free-thaw cycles on the mechanical behaviour of soils will be assessed. A better understanding of these effects will enable numerical tools to confidently characterize the anticipated field behaviour. Both monotonic and cyclic tests will be carried out under load, and displacement controlled loading modes to properly simulate the anticipated field loading. Triggering of liquefaction will be considered not only as a result of undrained loading, but also under partially drained conditions and under scenarios involving expansive drainage.