SANICLAY and SANISAND plasticity models: recent advances and applications

by Mahdi Taiebat of the Univeristy of British Columbia, Tuesday, May 16, 2017

Simplicity of structure and presentation versus sophistication of performance are the characteristics of constitutive models that must be properly balanced in order to achieve eventually being useful in practice. This can be accomplished without sacrificing the  igor of correct mechanics, and one of the simplest ways, is to present first the main building blocks of a model from the perspective of great simplicity. SANICLAY and SANISAND are families of Simple ANIsotropic CLAY and SAND plasticity models, developed over the last several years for application in geotechnical and earthquake engineering. They are within the useful framework of critical state soil mechanics, formulated based on bounding surface plasticity, and built on familiar foundations of Modified Cam-Clay and Drucker-Prager, respectively. The models in both class include anisotropy as one of their important ingredients for addressing monotonic and cyclic loading, and include multiaxial tensorial formulation. The contributions on these models over the years include various constitutive ingredients in the form of simple add-ons features that can be activated depending on the availability of data and needs of application. This presentation includes a general introduction to the basic features of these two families of soil plasticity models, and briefly reviews selected add-on features. Some examples of model validation and application will also be presented and discussed.


Risk Assessment in geotechnical Engineering - 2017 Spring CROSS CANADA LECTURE

by Dr. Vaughan Griffiths of the Colorado School of Mines, Wednesday April 12, 2017

Geotechnical engineering has seen a rapid growth of interest in risk assessment methodologies. This seems a logical evolution since soils and rocks are among the most variable of all engineering materials and geotechnical engineers must often make do with materials they are dealt with at any particular site. A probabilistic analysis may lead to a “probability of failure”, as opposed to the traditional “factor of safety”, representing a fundamental shift in the way engineers need to think about the suitability of their designs. The seminar will review some of the benefits and potential pitfalls of these different approaches and describe some introductory methods of probabilistic analysis.

Importance of Geology and Rock Mechanics in the Siting and Construction of Dams – The UBC Geological Engineering 2017 Distinguished Lecture

by Richard Goodman, Professor Emeritus, University of California (Berkeley), Thursday, March 23, 2017, Earth Sciences Building 1013, UBC

The serious difficulties with dam foundations containing soluble limestones and evaporates are well known and appreciated.  But important problems can also develop with dam foundations on non-soluble rock formations by virtue of geologic structural features. This lecture will describe a number of relevant and instructive case histories of dam safety reviews and the measures that were taken to assure foundation safety. These cases illustrate the importance of fully respecting and interpreting geologic and rock mechanics details in the siting and construction of dams.

Refreshments and mingling will run from 1730 to 1830.  The lecture will being at 1830.

Challenging Rock Slope Excavation and Remediation

by Charles Hunt, Wednesday, February 22, 2017

The technical issues associated with rock slope engineering are generally well known and understood. However, challenging, heterogeneous rock slopes require tailored solutions specific to controlling the rock fall hazard identified. The presentation will focus on overviewing such tailored solutions on a number of rock slopes with different hazards created by unique geological, slope and catchment characteristics. To categorize the examples they will be split into solutions with minimal catchment, solutions which required urgent time critical procurement of materials, and finally some innovative examples of remediation techniques where both the nature of the hazard and time/budget constraints necessitated creative thinking.

A Screening Tool for Impact Hammer Selection for Installation, Testing and Damage Mitigation for Open-Toe Steel Pipe and H-Piles

by David Tara, Thursday, February 2, 2017

In this talk David will share his experience in a presentation that will build on those given at GeoVancouver in October 2016. The presentation will cover some of the considerations involved in impact hammer selection for installation and high‑strain dynamic testing of open-toe, steel pipe and H‑piles:

  • minimum, suggested and maximum hammer size required for pile installation
  • minimum, suggested and maximum hammer size required for high-strain dynamic testing
  • maximum driving stresses
  • damage susceptibility relative to pile cross section dimensions
  • damage mitigation

The latter half of the talk will focus on the application of the screening tool to published case histories and data in David’s files. The applicability of the screening tool for impact hammer selection will be assessed and, with the aid of advanced pile driving simulation and signal matching software, to also show how pile damage could have been predicted.

VGS-TAC NEW YEAR'S PARTY

by Ross Varin, Tuesday, January 10, 2017

Engineers Without Borders will be giving a presentation on a project they are working on in Panama.   

RECENT TRENDS IN THE SAFETY ASSESSMENTS FOR TAILINGS DAMS

by Bryan Watts, Tuesday, November 29, 2016

This talk will be an encore presentation of this Keynote address on “Recent Trends in the Safety Assessments for Tailings Dams” given at the recent CDA conference in Halifax in mid-October.  Four case histories of tailings dam failures: Omai, Los Frailes, Mt. Polley, and Fundao are described together with their impact on tailings dam stewardship.  This is followed by a discussion of current trends in tailings dam management structures,  the continuing malaise in data organization at tailings dam sites, and the value of tying acceptable Factor of Safety guidelines to the ability to monitor the failure mode of interest.  

LIQUEFACTION AND SPATIAL VARIABILITY - 2016 FALL CROSS CANADA LECTURE

by Ross W. Boulanger, of the University of California Davis, Thursday, October 27, 2016

The development and application of engineering procedures for evaluating soil liquefaction during earthquakes rely heavily on case histories and their interpretations. Our ability to correctly interpret and utilize case history observations requires a sound understanding of the underlying physics, as is often derived from a synthesis of experimental and theoretical findings. In this regard, understanding the effects of spatial variability on liquefaction phenomena is essential for facilitating interpretation of case histories and application of liquefaction evaluation procedures.

In this presentation, nonlinear dynamic analyses of liquefaction in spatially variable (stochastic) deposits are used to draw insights on how spatial variability may affect the system performance and be appropriately accounted for in other types of analysis procedures. Results and insights are summarized for different types of problems: dynamic response and pore pressure generation as observed at the Wildlife liquefaction array; lateral spreading and surface settlements in gently sloping ground underlain by alluvium with different depositional structures; and deformations of an embankment dam underlain by a liquefiable alluvial layer. The practical lessons drawn from these simulations illustrate the complementary roles of theoretical, experimental, and case history based findings for advancing our ability to address liquefaction problems in engineering practice.

GROUND IMPROVEMENT AND LIQUEFACTION MITIGATION USING DRIVEN TIMBER PILES - AND ANNUAL GENERAL MEETING

by Armin W. Stuedlein of Oregon State University, Wednesday, September 14, 2016

Conventional driven timber pile ground improvement can provide a cost-effective liquefaction mitigation method, as it provides densification and reinforcement to an improved subgrade. The potential for drained timber piles to improve densification and potentially reduce in-earthquake pore pressures could allow densification, reinforcement, and drainage in one mitigation method. However, the soil densification possible with timber pile ground improvement is rarely incorporated into stability analyses of supported geostructures because of the current lack of understanding of the amount of densification possible. This study focuses on a field trial of driven conventional and drained timber piles to investigate the effect of pile spacing, time-since- installation, and drainage on the amount of soil densification. The test site consisted of clean to silty sands with a relative density ranging from 40 to 50 percent prior to installation. Following installation of the timber piles spaced at two, three, four, and five pile diameters, cone penetration tests were conducted to evaluate the degree of densification. These tests were performed at approximately 10, 50, 120, and 250 days following installation to evaluate the effect of time and to understand the role of fines content on the degree of densification. In general, the relative density of the soils improved to approximately 60 to 100 percent depending on the pile spacing and the presence of drainage elements. A controlled blasting test plan was also conducted at an un- improved control zone and in the improved timber pile test area to evaluate the effectiveness of this ground improvement alternative to reduce the excess pore-water pressures and mitigate liquefaction. The treated zones were shown to mitigate liquefaction by reducing the peak residual r u values 10 to 25 percent and lowering the soil settlements by approximately 75 percent compared to the un-improved zone.

The presentation slides are available here.