Dissertation Defence: Flow Liquefaction and Mobile Landslides Triggered Under Static Conditions: Insights From Case Studies on Tailings Dams, Earth Dams, and Glacial Slopes

Ali Babaki, supervised by Dr. Dwayne Tannant, will defend their dissertation titled “Flow Liquefaction and Mobile Landslides Triggered Under Static Conditions: Insights From Case Studies on Tailings Dams, Earth Dams, and Glacial Slopes” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.

An abstract for Ali Babaki’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. This exam will be offered in hybrid format. Registration is not required to attend in person; however, please email dwayne.tannant@ubc.ca to receive a Zoom link for this exam.

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Abstract

This thesis investigates the mechanisms and mobility of landslides triggered under static conditions, with a primary focus on flow liquefaction, also known as static liquefaction. Flow liquefaction is a critical failure mechanism in loose, saturated soils, leading to sudden strength loss and rapid debris movement. The research explores this phenomenon through detailed case studies of tailings dams, earth dams, and natural slopes in glaciofluvial terrains.

A decoupled numerical modelling framework integrating the Finite Element Method (FEM) with the Norsand constitutive model and the Material Point Method (MPM) was employed to simulate liquefaction initiation, propagation, and debris mobility. The Tar Island dyke case study demonstrated the effectiveness of this framework in capturing the onset of instability, delineating the extent of liquefaction, and predicting debris runout distances. The Edenville dam failure was re-evaluated to understand how static liquefaction can develop in water-retaining structures. The analysis highlighted the role of stress path evolution, particularly under Constant-Shear-Drained (CSD) conditions, in triggering instability. MPM simulations further revealed that delayed failure following initial deformation could increase saturation and liquefaction extent, leading to enhanced debris mobility.

In glaciofluvial terrains, two case studies investigated the high mobility of small landslides. The findings emphasized the importance of examining failure mechanisms at the landslide source area rather than focusing solely on runout path dynamics. Results also suggest that the combined effects of static liquefaction and drained shear strength reduction in stratified soils contribute to increased debris mobility.

This research underscores the importance of incorporating advanced numerical modelling techniques in assessing geohazards associated with static liquefaction. The proposed methodologies provide valuable insights for improving hazard assessment, risk mitigation strategies, and the design of safer earth structures. The outcomes contribute to a deeper understanding of the critical factors controlling static liquefaction and flowslides in both engineered and natural slopes.