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

液化描述了地震后饱和土壤的刚度和强度的损失。在过去的地震中，与液化有关的地面破坏一直是基础、桥梁和基础设施损坏的主要来源。粗粒桑迪的液化触发分析已经得到了很好的建立。然而，过去地震的历史证据表明，具有低至中等粘土含量（塑性）的细粒土壤也可能发生液化。这种土壤在安大略南部经常遇到。有必要对粘性土或粉质土的循环特性进行更明确的评估，以确保不忽视相关的液化风险。 建议的研究计划的主要目标是加强和扩展目前的做法，液化分析从砂到细粒粉质或粘性土。原位测试用于岩土工程中的地面表征，通常通过测量推锥阻力（qc）或地面中剪切波的速度（VS）。拟议的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）完成。他们将使用新型双向循环简单剪切仪、循环三轴试验进行广泛的系列试验，并使用创新的实验室规模物理模型校准锥形流变仪，然后将细粒土的循环阻力和液化潜力与qc和VS相关联。本研究计划中采用的实验室仪器将更好地模拟真实的地震荷载和现场边界条件。通过现场试验，将为细粒土的液化触发和震后地面沉降分析建立一个新的准则。这将是创新的，因为它将考虑双向循环荷载，土壤粘土含量（塑性），深度，地面坡度和先前的应力历史的影响。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。这将用于岩土工程的高级数值分析和抗震设计。 加拿大易受破坏性地震的影响，2012年不列颠哥伦比亚省北海岸发生的7.7级海达-格奥尔基（夏洛特女王）地震就证明了这一点。安大略地震可能特别具有破坏性，因为北美东部相对完整的地质和基岩有助于将地震振动传递到更远的距离。本文的研究成果将有助于改进加拿大的抗震设计规范和指南，为细粒土提供一种新的液化分析方法。这将最终导致更安全和具有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.