The Geotechnical Society of Edmonton is pleased to host its Annual Wine & Cheese Event and Fall Student Mixer Event, including presentation of the 2022 award recipients for the N.R. Morgenstern Student Award and CGS Graduate Student Paper Award.
2022 N.R. Morgenstern Student Award Recipient
Evaluation of the geomechanical behavior of fiber-reinforced clay soil
Akhila Palat is currently a post doctoral fellow in geotechnical engineering at the University of Alberta. She holds a PhD in Geotechnical engineering (University of Alberta), Master of Technology in Geotechnical engineering (Indian Institute of Technology, Hyderabad) and Bachelor of Technology in Civil Engineering (College of Engineering, Trivandrum). Her Ph.D. dissertation titled ‘Evaluation of the geomechanical behavior of fiber-reinforced clay soil’ focused on advanced soil mechanics and discussed the influence of randomly oriented discrete fibers on the strength and pore pressure response of fine-grained soils. Akhila is also a member of the Canadian Federation of University Women and the Edmonton Historical Board.
Existing models of soil behavior have been developed based on the understanding of interaction between particles, much of it is conceptually based on sand and modified to describe the behaviors of clayey soils. There are other classes of fibrous soils and soils amended with fibers for which the current understanding of soil behavior does not represent well. This study evaluates the role of discrete polymeric fibers in altering the geomechanical behavior of clay soil. Undrained triaxial compression and extension tests are performed on clay samples reinforced with polypropylene fibers. The influence of sample preparation techniques (compacting the soil to its optimum moisture content and placing hydraulically as a slurry) on the behavior of the soil-fiber composite is also analyzed. A novel transparent fiber-reinforced clay soil was prepared to analyze the orientation of fibers within the compacted and slurry samples. The limitations of traditional triaxial compression tests in predicting the strength of fiber-reinforced composites are discussed. The results of this research are anticipated to be applicable to estimate the undrained behavior and shear strength of fibrous organic soils and soils reinforced with elements that act in tension.
2022 Canadian Geotechnical Conference GSE Student Paper Award Recipient
Large-scale stiffness tests bounding a deep bedding plane in the Shaftesbury Shales
Mr. Dreger is a Geotechnical Engineer with eight years of experience in Alberta, British Columbia, Saskatchewan, Yukon, Northwest Territories, and Nunavut. After working in industry for five years, he returned to the University of Alberta to complete the M.Eng. program in geotechnical engineering and is now currently engaged in a doctorate program. During the first year of this program, he was seconded by SNC Lavalin to oversee production-scale lateral load testing at the Site C Hydroelectric Development as part of the Resident Engineering Team. Mr. Dreger is collaborating with industry leaders in the energy sector and in-situ testing practitioners to explore the constitutive behavior of argillaceous shales tested at various scales and degrees of disturbance. This research will inform performance-based design models by providing a basis for comparison between rock mass behavior and quantifiable performance objectives.
The powerhouse and spillway structures of the Site C hydroelectric project are founded on the Shaftesbury Shale. Deformation modulus testing for the foundations was carried out in the 1980s near a prominent clay-filled bedding plane shear at Elev. 415 m. The 2010 redesign of these structures on a RCC foundation deepened the excavations to Elev. 375 m to improve the foundation stiffness as bedding planes below Elev. 400 m lack the clay gouge observed at shallower depths. Recent pressuremeter testing was conducted to establish the deformation characteristics of the shale below Elev. 400 m, focusing on the stiffness around bedding planes. Initial investigations in the 1980s concluded that the deformation modulus was significantly reduced when determined using small scale in-situ or laboratory testing, owing to disturbance around borehole walls and stress-released samples. To validate this finding at depth, two split-lateral load tests were carried out above and below a bedding plane. The loading assemblies installed and concreted into two 2.6 m diameter drilled shafts comprised 2.3 m diameter steel casings with two laterally oriented O-cells expanding against diametrically-opposed segments – fundamentally a large Goodman Jack. Five SAAs measured rock mass deformations up to lateral loads of 81 MN. Rock mass deformations reached approximately 1 mm at maximum loads, indicating an elastic rock mass response. Numerical analyses carried out using FLAC3D to match the recorded rock mass deformations with load showed a deformation modulus of approximately 20 GPa and that the bedding plane had no influence on the stiffness. This presentation describes the testing procedure and analyses carried out to establish the in-situ rock mass deformation modulus at depth.