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

液化是指地震后饱和土壤的硬度和强度的丧失。在过去的地震中，与液化有关的地面破坏一直是地基、桥梁和基础设施受损的主要来源。对于粗粒砂土，液化触发分析已经得到了很好的证实。然而，过去地震的历史证据表明，具有低到中等粘粒含量(可塑性)的细粒土壤也可能发生液化。这样的土壤在安大略省南部很常见。为了确保相关的液化风险不被忽视，有必要对粘性土或粉质土的循环特性进行更明确的评估。 拟议研究计划的主要目标是加强和推广目前液化分析的实践，从砂土到细粒粉质或粘性土壤。在岩土工程中使用现场测试来表征地面特性，通常通过测量推锥阻力(Qc)或地面中横波的速度(Vs)来进行。建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。他们将使用一种新型的双向循环简单剪切仪进行广泛的一系列测试，循环三轴试验，并使用创新的实验室规模物理模型校准圆锥渗透仪，然后将细粒土的循环阻力和液化势与QC和VS联系起来。该研究项目中使用的实验室设备将允许更好地模拟真实的地震载荷和现场边界条件。随后，将通过现场测试的方法，为细粒土液化触发和震后地面沉降分析建立新的准则。这将是创新的，因为它将考虑双向循环加载、土壤粘粒含量(塑性)、深度、地面坡度和先前应力历史的影响。此外，还将建立和标定土的本构模型，以模拟细粒土的循环响应和液化行为。这将用于岩土工程中的高级数值分析和抗震设计。 加拿大很容易发生破坏性地震，2012年发生在不列颠哥伦比亚省北海岸的7.7级强烈地震海达格瓦(夏洛特女王)就证明了这一点。安大略省的地震可能会造成特别的破坏，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。研究的实际成果将有助于改进加拿大的抗震设计规范和指南，为细粒土液化分析提供一种新的方法。这最终将导致更安全、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.