PREVIOUS LECTURES

helical piles: efficient foundation for static, dynamic, and seismic applications

by Hesham El Naggar, Ph.D., P.Eng., FCAE, FEIC, FASCE - Professor at the University of Western Ontario, Monday, October 16, 2023 at 1730

Helical piles have become popular foundation option owing to their many advantages related to ease of installation and large load carrying capacity. They are typically manufactured of straight steel shafts fitted with one or more helices and are installed using mechanical torque. They can sustain static and dynamic loading and are increasingly used in applications that induce complex loading conditions on them. The behavior and design of single vertical helical piles subjected to static loading is well investigated. However, the dynamic and seismic behavior of single helical piles and their group behavior are of great importance in modern foundation engineering practice but not yet well understood. This presentation presents recent advances in evaluating the axial and lateral capacity and performance of single and grouped helical piles and their response to static, dynamic and seismic loads.

Tailings-Specific Liquefaction Assessment

by Mason Ghafghazi, Ph.D., Professor at the University of Toronto, Wednesday, May 17, 2023 at 1730

Tailings dams are man-made earth structures used for storing mining waste, comprised of water and fine minerals left behind from the extraction process. Tailings are usually non-plastic fine sand-and-silt-sizedsoils with angular particles that are often deposited in a loose state. The current practice mostly ignores the important differences among soils and how these differences influence CPT interpretation and calculation of residual shear strengths. Advances in CPT interpretation though still rely on CPT calibration chamber data on clean quartz sands. Case history based residual strength correlations do not account for differences among soils, how liquefaction was triggered, or system level differences.

Research done on various aspects of liquefaction assessment in tailings over the past few years at University of Toronto will be presented. This includes a new state parameter interpretation technique that provides soil-specific correlations by taking in Norsand’s parameters as input. It will be shown that this method estimates the in-situ state parameter more accurately than existing screening methods. Correlations between residual strength and state parameter are then presented based on laboratory tests on various gradations of tailings and natural soils. It will be shown that residual strength is soil-specific, and laboratory tests can be used in conjunction with case-histories to inform the level of conservatism in choosing residual strengths for design.

NEXT GENERATION LIQUEFACTION HAZARD ANALYSIS - DATA, ISSUES, AND MODEL DEVELOPMENT - Canadian geotechnical society cross Canada lecture tour (cclt) Spring 2023

by Dr. Steve Kramer, Professor Emeritus of the University of Washington, May 1, 2023 at 1730

The geotechnical engineering profession's understanding of soil liquefaction has advanced greatly since its effects were first widely observed following 1964 earthquakes in Niigata, Japan and Alaska. Both laboratory- and field case history-based approaches have illuminated liquefaction susceptibility, triggering, and consequences and developed useful tools for estimating each. Liquefaction models have historically been developed by small groups of researchers who have individually collected and interpreted laboratory and case history data. This has resulted in different models based on different data and different interpretations that can provide different results under conditions of interest in practice. The Next Generation Liquefaction (NGL) project was conceived of and designed to promote the development of liquefaction models based on consistent, publicly available, up-to-date field and laboratory data. This presentation will introduce the NGL project, discuss important issues relative to susceptibility, triggering, and consequences encountered in practice, and describe the innovative approaches taken to address them by the NGL modeling teams.

lESSONS LEARNED FROM THE SR-99 HIGHWAY TUNNEL PROJECT IN SEATTLE - OWNER’S PERSPECTIVE

by Gregg Korbin, Ph.D., Geotechnical Consultant on Thursday, April 13, 2023 at 1730.

The SR-99 highway tunnel under the city of Seattle was designed to replace the waterfront viaduct damaged by the Nisqually earthquake. At time of bid, the 17.5 m diameter EPBM manufactured by Hitachi was the world’s largest TBM. The speaker was a member of Washington State Department of Transportation’s (WSDOT’s) technical review board from design through construction (2009 to 2017). The project faced many technical challenges, and despite a difficult start up, it ended up setting a new standard for the soft ground tunneling industry in terms of ground control and monitoring methodologies. The technical presentation will be from the owner’s perspective. Topics include design and contract approach, TBM issues related to manufacturing, breakdown and rebuild, the management change, TBM performance and ground response from mining, and the court case, as well as the contribution of WSDOT’s technical review board.

SHEAR WAVE-VELOCITY OF LIQUEFIED SOIL: AN UPDATE

by Robert Kayen, Ph.D., Professor from UC Berkeley on Thursday, March 23, 2023 at 1730.

The shear-wave velocity (Vs) offers a means to determine soil's seismic resistance to liquefaction by a fundamental soil property. This talk will present the results of a decades-long international project to gather Vs site data and develop probabilistic correlations for seismic soil liquefaction triggering using shear wave velocity. The first correlation, published in 2013, analyzed 121 sites from the literature and 310 test sites we investigated in China, Japan, Taiwan, Greece, and the United States.

We are updating the initial correlation and have expanded the data set to approximately 650 sites, mainly through new testing of the M9.0 2011 Tohoku Earthquake, Japan, and the 2011 Christchurch and 2010 Darfield Earthquakes, New Zealand. Of critical importance, these new case histories occupy locations previously investigated by penetration testing. Bayesian regression and structural reliability methods facilitate a probabilistic treatment of the Vs catalog for performance-based engineering applications. Analysis of the uncertainties of the variables comprising both the seismic demand and the soil capacity is integral to the study and allows for the reduction of overall model error.

MINING, SUSTAINABILITY, AND MINE DESIGN CRITERIA IN THE CONTEXT OF A CHANGING SOCIETY

by Dr. Anthony Hodge, P.Eng., Professor from UBC on Tuesday, March 28, 2023 at 1800.

During the last half century, mining practices have been increasingly examined through the lens of their short and long-term impacts to human and ecological well-being. The result has often been tension, as today’s insights and values challenge those of the past. This tension touches not only on the technical content of decisions but also the nature of how decisions are made. And it continues at a time when society’s need for mined materials continues to increase, particularly in support of the world’s transition to a low-carbon economy. This lecture discusses some of the major changes that the mining industry has experienced, and how a quest for fairness is central to effective mine design and implementation and reduction of the trust-deficit that exists between mining and society.

Field Trials of microbially induced desaturation for earthquake liquefaction mitigation in portland, oregon

by Diane Moug, Ph.D., Assistant Professor from Portland State University on Thursday, February 23, 2023 at 1730.

Earthquake liquefaction hazards in silty soils are a critical problem in Portland, Oregon and other areas around the world. This is a particular problem for existing facilities founded upon silty liquefiable soil, for which there exists no cost-effective mitigation solution at the present time. Recent studies suggest that liquefaction mitigation using microbially-induced desaturation (MID) may provide the capability to do this. MID treatment can be performed by injecting a treatment solution into liquefaction-prone soils. The treatment solution stimulates growth of native bacteria that produce nitrogen gas as a biproduct. The objective of MID is to reduce earthquake-induced excess pore water pressure generation compared to saturated soil, and thereby reduce the potential for triggering liquefaction. This presentation will describe two field trials of MID for liquefaction mitigation performed in Portland, OR in summer 2019. Low-plasticity, liquefiable silts were treated with MID by injecting a treatment solution to stimulate native bacteria for a duration of four weeks. Migration of the treatment solution and saturation ratios were monitored with a range of methods, including: crosshole pressurewave velocity measurements, a vertical array of embedded sensors that measure water content and bulk electrical conductivity, pre- and post-treatment seismic cone penetration tests, and direct soil sampling of the treated soils. Monitoring at both sites indicated that liquefiable silts were successfully desaturated and that desaturation has sustained for over 3 years.

bridges to prosperity - 2022 cyarera bridge project - joint event with the tunnelling association of canada (TAC)

by Heather Hughes-Adams, from McMillen Jacobs on January 24, 2023 at 1700.

Sustainable practices for geotechnical engineering - canadian geotechnical society cross canada leCture tour (cclt) fall 2022

by Catherine Mulligan, PhD - Professor, from Concordia University on November 29, 2022 at 1730.

Due to depletion of natural resources, increased natural disasters, waste, greenhouse gas emissions, pollutant generation, and environmental deterioration, and loss of biodiversity, geotechnical engineers are facing new challenges. While it is generally believed that the concepts of sustainable development must be followed for protecting future generations, it is much easier said than implemented. Therefore, the focus of this talk will be to focus on the application of the principles of sustainable geoengineering to projects and processes. Some tools and frameworks for evaluating and implementing sustainable practices will be presented. The use of environmental, social and economic indicators for measuring and comparing design options will be demonstrated. Best practices in carrying out Indigenous engagement and consultation will be highlighted. Finally, case studies and examples of sustainable practices in design in addition to the challenges and needs for the future will be included. The role of geotechnical engineers in sustainable development has been undervalued but is critical for future generations.

Changes in Seismic site response analysis approach to be consistent with the 6th generation seismic hazard model of canada

by Chris Weech, M.A.Sc., P.Eng from Thurber Engineering on November 16, 2022 at 1730.

In NBC 2015, amplification factors, F(T), were provided which varied based on seismic site class and the site-specific probabilistic PGA for a Site Class C reference ground condition (PGAref) at the specified hazard level. In the 6th Generation Seismic Hazard Model of Canada (SHMC-6) adopted for NBC 2020, multiple ground motion models (GMMs) are used to calculate hazard values at ground surface which include site amplification effects calculated internally using site terms specific to each GMM. Linear amplification effects are calculated based on Vs30. Non-linear amplification effects are calculated using site terms that vary as a function of the median prediction of ground motion intensity associated with each event scenario considered in the hazard model. The amplified ground motion values for each event scenario are then aggregated to generate the probabilistic hazard values for a particular site location and Vs30.

This presentation will discuss the fundamental differences in the way that amplification is treated in NBC 2015 and SHMC-6. The results of a study that was carried out to implement SSRA-based amplification functions within SHMC-6 will be presented. The probabilistic UHRS generated using the rigorous method will be compared to SSRA-based UHRS generated using the NBC 2015-compatible SSRA methodology as well as a modified procedure for carrying out SSRA in a manner that is consistent with the way that non-linear amplification is treated in SHMC-6.