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

土壤特定液化评估框架的开发：土壤级配的作用

• 批准号: RGPIN-2016-05622
• 负责人: Ghafghazi, Mohsen
• 金额: $ 1.68万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=615810
• 关键词: Development; Soil; Specific; Liquefaction; Assessment

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.

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。实践依赖于现场贯入试验和土壤循环响应之间的基于案例历史的关系。除了对细粒含量的修正知之甚少外，具有不同成分和级配以及各种机械性能的土壤基本上被视为均匀级配的石英砂。在2008年中国汶川地震中，现有的方法无法预测几乎所有广泛级配碎石土液化导致广泛破坏的场地的液化。 土的级配对粘性和压缩性以及颗粒破碎有一级影响，这些因素以不同的方式控制着土的贯入阻力和循环响应。以往的研究表明，较宽的级配对循环阻力的影响很小，但对贯入阻力的增加更明显。因此，具有与均匀砂相似贯入阻力的宽级配土壤的循环响应明显较弱。 该研究项目的短期目标是开发一个机械框架，解释级配对无粘性土壤循环响应的一般影响，以及用于现场评估的贯入阻力。这项工作将为现有的细粒含量校正提供科学的解释，并将概念扩展到包括具有显著砾石含量的所有宽级配土壤。长期目标是开发实用的，经过充分验证的，土壤特定的液化标准，考虑到独立可测量的土壤特性。 四个具体组成部分旨在（i）量化级配对粘性、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）对静力触探试验进行建模并研究级配对其测量的影响，以及（iv）为基于案例历史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，研究将减少处理偏离理想均匀砂情况的土壤时的重大不确定性。如果当前的保守主义导致不必要的补救工作，则可以实现巨大的经济收益，并通过识别未识别的液化危害来降低风险。 该研究计划将创造一个互动的环境，本科生，硕士和博士生进行先进的实验室测试和创新的数值分析将相互合作，并与来自行业和学术界的领先的国家和国际专家。