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: 250368-2012
• 负责人: Sivathayalan, Siva
• 金额: $ 1.75万
• 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: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=570906
• 关键词: Characterization; soil; behaviour; earthquake; engineering

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.

对土壤特性的基本了解主要来自完全排水或完全不排水条件下的实验室试验，以及沿特定应力路径的试验。在现实中，地应力路径将由所有三个主应力的变化决定，而变形总是涉及孔隙体积和孔压的同时变化。虽然排水和不排水的近似可能适用于特定的情况，取决于土壤的渗透性和加载速率，但在某些情况下，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，试图防止生命线故障和减轻地震造成的破坏往往会导致巨大的经济成本。目前的抗震设计方法一般是保守的，因为它主要依靠经验数据来评估液化危险。更好地了解土壤在实际现场加载路径和排水条件下的行为，对于成功地表征土体在地震期间的反应是至关重要的。这样的理解将有助于制定全面的模型，从而能够可靠地预测岩土结构在外加荷载下的反应。 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和解决与全球变暖和可持续发展有关的关切至关重要。考虑孔体积和压力同时变化的现场表征方法将产生更有意义的结果。拟议的研究结果将直接有助于尾矿和水电站大坝的安全，并使全国各地有问题的土壤能够进行有信心的设计。 建议研究的目的是评估初始状态、广义应力路径和部分排水对土的静力和地震响应的影响。为了从根本上理解剪切-体积耦合变形对本构关系和液化敏感性的影响，将进行一项系统的研究，分离并探索每个变量。一般的初始应力条件、应力路径和排水程度对土体的应力-应变行为及其失稳特性的影响将通过三轴、单剪和中空圆柱体试验来评估。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现场行为。在加载和位移控制加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。液化的触发将不仅被认为是未排水载荷的结果，而且在部分排水条件下和在涉及膨胀排水的情况下也被考虑。