Development of a Soil-Specific Liquefaction Assessment Framework: Role of Soil Gradation

液化敏感性及其后果评价是岩土地震工程的重要组成部分。这一实践依赖于现场贯入试验与土体循环响应之间的基于实例的关系。除了对细粒含量的校正知之甚少外，不同组成和级配、力学性质差异很大的土壤基本上被视为均匀级配的石英砂。现有的方法无法预测在2008年中国汶川地震期间，广泛级配的砾石土液化导致广泛破坏的几乎任何场地的液化。*土级配对膨胀性和压缩性以及颗粒破碎具有一阶效应，这些因素以不同的方式控制土体的渗透阻力和循环响应。以往的研究表明，较宽的级配对循环阻力的影响很小，但对渗透阻力的影响更为显著。因此，具有与均匀砂相似的贯入阻力的广级配土壤的循环响应可能明显较弱。*该研究计划的短期目标是开发一个机械框架，解释级配对无粘性土循环响应的一般影响，以及用于现场评估的渗透阻力。这项工作将对现有的细粒含量修正提供科学解释，并将这一概念扩展到包括所有广泛分级的土壤，包括那些砾石含量较高的土壤。长期目标是开发实用的、经过充分验证的、特定于土壤的液化标准，该标准考虑到独立可测量的土壤特性。*四个具体组成部分旨在(I)量化级配对膨胀性、压缩性、颗粒破碎和循环响应的影响，(Ii)量化现场和实验室土壤结构对行为的影响，(Iii)模拟圆锥贯入试验并研究级配对其测量的影响，以及(Iv)为基于案例的方法和验证开发一般级配校正。*通过将土壤特性的影响整合到当前的液化评估实践中，这项研究将减少在处理偏离理想的均匀沙子情况的土壤时的显著不确定性。在当前的保守主义促使不必要的补救工作的情况下，可以实现巨大的经济收益，并将通过识别未识别的液化危险来降低风险。*该研究计划将创造一个互动环境，在这个环境中，进行高级实验室测试和创新数值分析的本科生、硕士和博士生将相互合作，并与来自行业和学术界的国内和国际顶尖专家合作。

Assessment of liquefaction susceptibility and its consequences is a major part of geotechnical earthquake engineering. The practice relies on a case-history-based relation between in-situ penetration tests and cyclic response of soils. Apart from a poorly understood fines content correction, soils with different compositions and gradations and widely varied mechanical properties are essentially viewed as uniformly graded quartz sand. The existing methods would not have predicted liquefaction in almost any of the sites where liquefaction of widely graded gravelly soils resulted in widespread damage during the 2008 Wenchuan, China earthquake. ***Soil gradation has a first order effect on dilatancy and compressibility, as well as particle breakage; factors that control the penetration resistance and cyclic response of soils in different ways. Previous research suggests that wider gradation has a marginal effect on cyclic resistance, but imposes a more pronounced increase on penetration resistance. Consequently, widely graded soils with similar penetration resistance to uniform sands can have a significantly weaker cyclic response. ***The short-term goal of the research program is to develop a mechanistic framework that explains the general effects of gradation on the cyclic response of cohesionless soils and the penetration resistance used for its in-situ evaluation. The work will provide a scientific explanation of the existing fines content correction, and expand the concept to incorporate all widely graded soils including those with significant gravel content. The long-term goal is developing practical, well-validated, soil-specific liquefaction criteria that take into account independently measurable soil properties.***Four specific components aim at (i) quantifying the influence of gradation on dilatancy, compressibility, particle breakage, and cyclic response, (ii) quantifying the influence of field vs. laboratory soil fabric on behaviour, (iii) modelling the Cone Penetration Test and investigating the influence of gradation on its measurements and (iv) developing general gradation corrections for the case-history-based method and validation.***By integrating the influence of soil properties into the current liquefaction assessment practice, the research will reduce the significant uncertainty in dealing with soils that deviate from the idealised uniform sand case. Large economic gains can be realised where current conservatism prompts unnecessary remedial work, and risk will be reduced by identifying unrecognised liquefaction hazard.***The research program will create an interactive environment where undergraduate, master's and PhD students performing advanced laboratory tests and innovative numerical analyses will collaborate with each other, and with leading national and international experts from both industry and academia.