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

液化敏感性及其后果的评估是岩土地震工程的一个重要组成部分。该实践依赖于现场渗透测试和土壤循环响应之间基于案例的关系。除了对细粉含量修正知之甚少之外，具有不同成分和级配以及广泛变化的机械性能的土壤本质上被视为均匀级配的石英砂。在 2008 年中国汶川地震期间，大级配砾石土的液化导致了广泛的破坏，现有方法无法预测几乎所有地点的液化。 ***土级配对剪胀性和压缩性以及颗粒破碎具有一级效应；以不同方式控制土壤的渗透阻力和循环响应的因素。先前的研究表明，较宽的级配对循环阻力有边际影响，但对渗透阻力有更明显的增加。因此，具有与均匀沙子相似的渗透阻力的广泛分级的土壤可能具有明显较弱的循环响应。 ***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其现场评估的渗透阻力。这项工作将为现有的细粉含量修正提供科学的解释，并将这一概念扩展到包括所有广泛级配的土壤，包括那些具有大量砾石含量的土壤。长期目标是制定实用的、经过充分验证的、针对特定土壤的液化标准，其中考虑到可独立测量的土壤特性。***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) 量化现场与实验室土壤结构对行为的影响，(iii) 模拟锥体渗透测试并研究级配对其测量的影响，以及 (iv) 制定通用标准基于案例历史的方法的级配修正和验证。***通过将土壤特性的影响纳入当前的液化评估实践中，该研究将减少处理偏离理想化均匀砂情况的土壤时的显着不确定性。当前的保守主义促使不必要的补救工作可以实现巨大的经济收益，并且通过识别未被识别的液化危险可以降低风险。***该研究项目将创建一个互动环境，本科生、硕士生和博士生将在其中进行高级实验室测试和创新数值分析，并与来自工业界和学术界的领先的国内和国际专家相互合作。

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.