Characterization of soil behaviour for earthquake engineering applications

对土壤行为的基本认识主要来自在完全排水或完全不排水条件下以及沿着特定应力路径进行的实验室试验。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。虽然排水和不排水的近似可能适用于具体情况，这取决于土壤的渗透性和加载速率，但在一些情况下，这种近似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，在地震发生时防止生命线失效和减轻损害的尝试往往会导致巨大的经济成本。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。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，对于成功地表征地震过程中土体的反应至关重要。这样的理解将使综合模型的形成成为可能，从而对土工结构在施加荷载作用下的反应作出可靠的预测。更好地了解环境因素对土壤行为的影响对于追求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矿山尾矿和水电站大坝的安全，并使在全国范围内有问题的土壤中进行可靠的设计。提出的研究目标是评估初始状态、广义应力路径和部分排水对土壤静力和地震反应的影响。将进行系统的研究，分离和探索这些变量中的每一个，以提供对剪切-体积耦合变形对本构关系和液化敏感性的影响的基本理解。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征的影响将通过三轴、简单剪切和空心圆柱体试验进行评估。此外，还将评估颗粒形状、过度固结和自由融化循环对土壤力学行为的影响。更好地了解这些影响将使数值工具能够自信地描述预期的场行为。单调试验和循环试验将在荷载和位移控制荷载模式下进行，以适当地模拟预期的现场荷载。液化的触发不仅要考虑不排水荷载的结果，而且要考虑部分排水条件和膨胀排水的情况。

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.