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

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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.