Settlement and Liquefaction Behaviour of Fine-grained Soils due to Seismic Loading

液化描述的是地震后饱和土壤刚度和强度的损失。在过去的地震中，与液化有关的地面故障一直是地基、桥梁和基础设施受损的主要原因。粗粒沙土液化触发分析已经建立。然而，过去地震的历史证据表明，粘土含量低至中等（塑性）的细粒土也可能发生液化。这种土壤在安大略省南部经常遇到。对粘土或粉质土的循环行为进行更明确的评估是必要的，以确保相关的液化风险不会被忽视。******提出的研究计划的主要目标是加强和扩展目前的液化分析实践，从砂到细粒粉质或粘土土壤。原位测试在岩土工程中用于地面表征，通常通过测量推动锥体的阻力（qc）或横波在地面的速度（VS）。研究计划将由申请人、5名研究生（2名MESc， 3名博士）和4名本科生（UG）共同完成。他们将使用一种新型的双向循环简单剪切装置进行一系列广泛的测试，循环三轴测试，并使用一种创新的实验室规模物理模型校准锥贯仪，然后将细粒土壤的循环阻力和液化潜力与qc和v相关联。本研究项目中使用的实验室设备将能够更好地模拟真实的地震载荷和现场边界条件。在此基础上，建立了细粒土液化触发和地震后地基沉降原位试验分析的新准则。这将是创新的，因为它将考虑双向循环加载、土壤粘土含量（塑性）、深度、地面坡度和先前应力历史的影响。还将开发和校准土壤本构模型，以模拟细粒土的循环响应和液化行为。这将应用于岩土工程的高级数值分析和抗震设计。******加拿大容易受到破坏性地震的影响，2012年在不列颠哥伦比亚省北部海岸发生的7.7级强震就是证明。安大略地震的破坏性可能特别大，因为北美东部相对完整的地质和基岩有助于将地震的振动传播到更远的地方。该研究的实际成果将有助于通过一种新的细粒土液化分析方法来改进加拿大的抗震设计规范和指导方针。这将最终导致更安全、更具成本效益的抗震设计规定。

Liquefaction describes the loss of stiffness and strength of a saturated soil following an earthquake. Liquefaction-related ground failures have been a primary source of damage to foundations, bridges and infrastructure during past earthquakes. Liquefaction triggering analysis has been well-established for coarse-grained sandy soils. However, historical evidences from past earthquakes demonstrate that fine-grained soils with low to moderate clay content (plasticity) may also undergo liquefaction. Such soils are frequently encountered in southern Ontario. A more explicit assessment of the cyclic behavior of clayey or silty soils is necessary to ensure that the associated liquefaction risks are not overlooked.******The main objective of the proposed research program is to enhance and extend the current practice in liquefaction analysis from sands to fine-grained silty or clayey soils. In-situ tests are used in geotechnical engineering for ground characterization, often by measuring the resistance of pushing a cone (qc) or the velocity of a shear wave (VS) in the ground. The proposed research program will be accomplished by the applicant, 5 graduate (2 MESc, 3 PhD), and 4 undergraduate (UG) students. They will carry out extensive series of testing using a novel bidirectional cyclic simple shearing apparatus, cyclic triaxial testing, and calibrate a cone penetrometer using an innovative laboratory-scale physical model, and then relate cyclic resistance and liquefaction potential of fine-grained soils to qc and VS. The laboratory apparatuses employed in this research program will allow a better simulation of real seismic loads and field boundary conditions. A new guideline will be subsequently established for liquefaction triggering and post-earthquake ground settlement analysis in fine-grained soils by means of in-situ testing. This will be innovative as it will account for the effects of bi-directional cyclic loading, soil clay content (plasticity), depth, ground slope, and prior stress history. A soil constitutive model will be also developed and calibrated to simulate the cyclic response and liquefaction behavior of fine-grained soils. This will be employed in advanced numerical analysis and seismic design in geotechnical engineering. ******Canada is vulnerable to destructive earthquakes, demonstrated by the powerful 7.7 magnitude Haida Gwaii (Queen Charlotte) earthquake that shook the north coast of British Columbia in 2012. Ontario earthquakes could be particularly damaging as the relatively intact geology and bedrock of eastern North America helps to transmit earthquake vibrations over greater distances. The practical outcomes of the proposed research will help to improve Canadian seismic design codes and guidelines by a new liquefaction analysis method for fine-grained soils. This will ultimately lead to safer and cost-effective seismic design provisions.