Geotechnical Society of Edmonton

NEWS 2014

Posted October 2, 2014 (Updated October 30, 2014)

Event: November 6, 2014

GSE: Tim Keegan, Ph.D., P.Eng. and Matthieu Sturzenegger, Ph.D. P.Geo., Klohn Crippen Berger - Construction of a composite barrier wall/rock shed structure at mile 109.43 of CNR's Ashcroft Subdivision and LiDAR and discrete fracture network modeling for rockslide characterization and analysis

Location: Saskatchewan Room, Faculty Club, University of Alberta (11435 Saskatchewan Drive)

Time: 5:30pm Registration, 6:00pm Dinner, 6:30pm Presentation

Cost: $30 Members, $40 Non-members, $10 Students (Payment Options)

Confirm Attendance (By noon on November 4)

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On November 25th, 2012 a 53,000 m3 rockslide buried the Canadian National Railway (CNR) track at Mile 109.4, Ashcroft Subdivision, near Boston Bar, causing a 4-day service disruption on their main east-west railway connection. The rock landslide resulted in the collapse of a 21 m long concrete rock shed originally designed to protect the railway from debris raveling out of a gully above the track. The landslide rupture surface is composed of vertical release fractures and exposed day-lighting discontinuities. A number of rock and debris landslide hazard types are identified in the post-landslide slope. The magnitudes, frequencies, and seasonal occurrences estimated for these hazards posed a significant short and long term risk management challenge for construction of the track protection structure. The presentations focus on lessons learned during ground hazard assessment, design and construction of a new 80 m long track protection structure. The first construction challenge was the short term protection of the work site from raveling rocks. This was managed with a rock fall mesh attenuation curtain combined with safe work protocol. The permanent composite barrier wall/rock shed structure consists of a tied-back, gravel-filled barrier wall designed to absorb a large portion of the impact loads during a future rock landslide event, and a rock shed allowing the rock landslide to safely travel over the railway track. All components are modular, facilitating construction under railway traffic to meet the goal of reducing track service disruptions. The triggering factors and the failure mechanism were further studied based on a combination of air-borne and terrestrial LiDAR data, site investigation and discrete fracture network (DFN) modeling. This work provided input parameters for subsequent run-out analysis and design of the railway protection structure.

Dr. Keegan a senior geotechnical/geological engineer, has spent the majority of his professional career, which spans 30 years, managing operational risk associated with geotechnical hazards and design, construction and operations in water retention dams, tailings containment, water supply, waste water management, pipelines, and railway operating environments. He has developed and implemented a variety of operational risk management systems including a methodology to manage the risks associated with geohazards along linear infrastructure and dam systems in an operational environment. He has extensive domestic and international experience in geological & geotechnical engineering applied in the areas of roads, railway, pipelines, water resource dams, tailing containment & dams, heavy civil, environmental remediation, mining and infrastructure projects. Selected experience related to geotechnical/geological engineering, risk management along transportation corridors, tailings facilities, dam safety review, design & construction and operational risk management.

Dr. Sturzenegger is an Engineering Geologist specializing in rock slope engineering and structural mapping. He has conducted geologic site characterization and stability analysis as part of design work in open pit mine and embankment tailings dam projects, and for hydroelectric dam abutment inspection in British Columbia, Washington State and Romania. He also worked on railway right of way rockslide and rockfall hazard assessment in British Columbia. The main focus of his Ph.D. research included structural characterization of rock mass discontinuities and numerical modelling for slope design and stability assessment. In particular, he used and developed descriptive and quantitative approaches for discontinuity characterization using terrestrial remote sensing techniques, such as digital photogrammetry and laser scanning. These techniques were applied at various locations along the West Coast of Canada, in the Canadian Rocky Mountains and in South Africa.

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