on the Important of kinematice in the analysis of (large) landslides - 2015 Spring CROSS CANADA LECTURE TOUR

by Dr. Nicholas Sitar, P.h.D., P.Eng., Thursday, May 14, 2015

The most convenient methods of slope stability analysis rely on limit equilibrium solutions which assume a pre-determined slide plane geometry and rigid body deformation.  However, many, particularly very large landslides are composed of many individual blocks that may be toppling, rolling or otherwise moving downslope in a manner inconsistent with the above assumptions. Example results of discrete body deformation modeling will be used to show that in such cases the traditional limit equilibrium methods would lead to erroneous and possible very unconservative conclusions.

2014 SR 530 LANDSLIDE (OSO, WASHINGTON, USA) - A MECHANISTIC INTERPRETATION OF INITIATION AND MOVEMENT

by Timothy D. Stark, Ph.D. and Oldrich Hungr, Ph.D., Wednesday, April 15, 2015

This presentation will focus on current research regarding the March 22, 2014 SR530 Landslide in Washington, USA.  This major, tragic landslide exhibited some particular aspects of geo-mechanical behavior. Its detailed study by several groups of specialists will contribute to better understanding of landslide mechanisms and to improved methods of hazard and risk assessment. The on-going research is focused on landslide triggering and runout of the slide mass. In particular, Professor Stark will focus on the field and laboratory investigations, slope stability analyses, and triggering aspects of the landslide and Professor Hungr will focus on the runout mechanism and distance.

PROBABILISTIC SEISMIC HAZARD ASSESSMENT (PSHA) - AN OVERVIEW

by Tuna Onur, Ph.D., Wednesday March 25, 2015

There are broadly two questions that need to be answered in order to understand the potential for earthquake shaking regionally or at a specific site: 1) Where and how frequently do various types and magnitudes of earthquakes happen? (Seismic Source Characterization), and 2) When these earthquakes happen, how much does the ground shake in locations of interest? (Ground Motion Characterization). PSHA provides a quantitative solution to the problem of evaluating earthquake shaking potential by integrating across these two components (seismic sources and ground motion) in a probabilistic framework. It currently forms the basis for seismic provisions in most structural design codes, when conducted regionally; and underpins site-specific design ground motions for critical facilities at long return periods. This presentation will describe the overall PSHA methodology and its basic components, and provide examples of its utilization, both in a regional and site-specific manner.

FAILURE AND POST-FAILURE ANALYSIS OF SUBMARINE MASS MOVEMENT - THE GEOLOGICAL ENGINEERING 2015 DISTINGUISHED LECTURE

by Professor Jacques Locat, Wednesday March 11, 2015

Multibeam sonar and seismic (2D and 3D) surveys provide excellent tools to ascertain the morphology of the sea floor. By investigating the morphology of the starting zone and of the depositional zone one can use that information for estimating various parameters needed for both failure and post-failure analysis. In many cases, the required reduction in shear strength is linked either to the effects of earthquake, gas hydrates or pore pressures with a strong influence of layering. In order to provide a rationale for estimating the magnitude of these triggering mechanism, one must make sure that the consolidation state of the sediment before failure is evaluated in order to carry a relevant back analysis. However, geotechnical cores are not always available and one must extract as much information as possible from geomorphologic and lithological data. For example, this may involve reading the morphology of the failure zone and relating it to slope forming processes. It may also imply distinguishing between slopes formed by sedimentation from those generated by erosion. Similarly, a geomorphological approach can also be used to estimate the yield strength mobilized for observed debris flow deposits, and the run out morpho-stratigraphic characteristics of that mass flow deposit can also be used to evaluate the tsunamigenic potential of the original slide! This approach will be illustrated and discussed in the light of recent studies carried on mass movements in various marine environments in North America and in Europe.

THE 22 MARCH 2014 OSO, WASHINGTON, USA, LANDSLIDE

by Dr. Joseph Wartman, P.E., Thursday, February 19, 2015

The Oso Landslide occurred on the morning of Saturday, 22 March 2014, and claimed the lives of 43 people, making it the deadliest landslide disaster in the history of the continental United States. The landslide initiated within an approximately 200-m-high hillslope comprised of unconsolidated glacial and colluvial deposits; it rapidly transitioned to a debris flow/debris avalanche that rapidly inundated a neighborhood of approximately 35 single-family residences. An intense 3-week rainfall that immediately preceded the event is believed to have played a major role in triggering the landslide. In this talk, I will present the findings of our Geotechnical Extreme Events Reconnaissance (GEER) Association scientific research team that performed a field reconnaissance of the Oso Landslide shortly after its occurrence. The talk will focus on observations made and data collected at the landslide site, but will additionally review regional and local geologic conditions, climate setting, eyewitness accounts, and land-use history. In addition, newly published findings and current debates on the landslide will be discussed.

R.F. LEGGET MEDAL DINNER IN HONOUR OF PROFESSOR EMERITUS PETER M. BYRNE

Tuesday, February 3, 2015 from 1730 to 2100; Registration is limited to 100 participants with a deadline of January 23.

Dr. Peter M. Byrne was the 2014 recipient of the Canadian Geotechnical Society’s R.F. Legget Medal; the society’s most prestigious award. The award was given at the CGS annual conference in Regina in November. However, Dr. Byrne was unable to attend the ceremony. In light of Dr. Byrne’s significant contributions to local geotechnical practice, the Vancouver Geotechnical Society is holding this dinner in honour of Dr. Byrne and to present him with the award in person.

The agenda for the evening includes the award presentation and dinner with five short technical presentations by Dr. Byrne’s former graduate students.

DEVELOPING CONFIDENCE IN CRITICAL STATE SOIL MECHANICS

A two-day workshop by Mr. Mike Jefferies and Dr. Dawn Shuttle, Friday & Saturday, January 16 & 17, 2015

The aim of this workshop is for all attendees to become confident in using CSSM across a spectrum of applications from assessing laboratory data through to developing design parameters. Confidence will be achieved by minimizing presentations in favour of participants being guided through developing their own spreadsheets to model soil behaviour – an approach insisted on three decades ago by Peter Wroth as the only way to grasp CSSM and still valid today. Once working spreadsheets have been created, participants will be guided through calibration of soil properties and onto modelling sample disturbance.

Laboratory data will be provided on Fraser River sand for use by workshop participants, but participants are encouraged to bring their own triaxial data (test requirements will be circulated to registered participants before the workshop). This workshop can be viewed as a further step from the May 2014 VGS short course by Professor Malcolm Bolton, and will focus on “how” rather than extended lectures about “what”. The models developed in the course will start with Original Cam Clay (the initial theoretical model) discussed by Professor Bolton, and then move on to NorSand (which works with real soils).

OFFSHORE FOUNDATION SYSTEMS - ROLE OF GEOTECHNICAL CENTRIFUGE MODELING - 2014 FALL CROSS CANADA LECTURE TOUR

by Ryan Phillips, Ph.D., P.Eng., FEIC, Thursday November 27, 2014 -- CANCELED DUE TO FLIGHT DELAY 

A video of the same presentation can be downloaded here. 

Offshore geotechnical engineering needs physical measurements to calibrate designs. Centrifuge modelling is increasingly accepted by industry to provide such a data source. An overview of centrifuge scaling principles and limitations will be presented. Several actual applications will be described, including jacket pile foundations, suction caissons, riser-seabed interaction and pipeline design against ice gouging. The results provided important insight into prototype behaviour and agree well with available full scale measurements.

INSTRUMENTED BECKER PENETRATION TEST FOR LIQUEFACTION ASSESSMENT IN GRAVELLY SOILS

by Dr. Mason Ghafghazi, P.Eng., Wednesday, November 12, 2014

Characterisation of cohesionless soils is of interest to a number of geotechnical problems, including liquefaction potential assessment. In gravelly soils found in most alluvial deposits, performance of conventional methods such as SPT and CPT are adversely affected by the presence of larger particles. The Becker Penetration Test (BPT) is a widely used tool for characterisation of gravelly soils in North America. The test is performed by driving a closed ended pile into the ground and reporting the number of blows per foot of penetration after correcting for the hammer energy. Interpretation of data obtained using the conventional BPT system to estimate soil properties below the driving shoe has significant challenges. The main source of the difficulty is that a large percentage of the energy delivered by the hammer is absorbed by the frictional resistance developed along the pile shaft. The instrumented Becker Penetrometer (iBPT) bypasses the shaft resistance issue by directly measuring the energy transferred from the driving shoe to the underlying soil. 

The presentation slides are available here.

Evaluating soil liquefaction using the CPT – practical considerations

by Dr. P.K. Robertson, P.Eng., Tuesday, October 7, 2014

Evaluating the potential for soil liquefaction and the resulting consequences is often a major design issue for many geotechnical projects in seismic areas. This presentation will provide some brief background on the available methods and present examples to illustrate some key points. Practical issues that influence the results will be discussed and presented.

The presentation slides are available here.

Selection and Modification of Time-Histories for Southwestern B.C.

by Tuna Onur, Ph.D., Thursday, September 18, 2014

Southwestern BC is situated in the Cascadia Subduction Zone and can be impacted by three distinct types of earthquakes: Deep earthquakes in the subducting Juan de Fuca Plate, shallow crustal earthquakes in the overriding North America Plate and giant earthquakes (Mw~9.0) at the interface of the two plates.  Probabilistic seismic hazard assessments that form the basis of design ground motions in Canada take into account all these sources of seismic activity to produce a uniform hazard spectrum (UHS).  After a brief overview of earthquakes in southwestern BC and calculation of design ground motions, this presentation focuses on various approaches to selecting and modifying time-histories to be compatible with the UHS.  Related issues that are discussed include de-aggregation of hazard, use of artificial versus real records, sources of processed and unprocessed strong motion recordings that are appropriate for the tectonic setting in southwestern BC, and time-domain, frequency-domain and hybrid methods for scaling and modifying time-histories.

The presentation slides are available here.