Tom Edwards

Fiber Optic Strain Monitoring and Evaluation of a Slow-Moving Landslide Near Ashcroft, British Columbia, Canada

Landslides in British Columbia are costly geological hazards that have challenged the major rail companies for over 120 years. Presented here are preliminary results and analyses of fiber Bragg grating and Brillouin optical time domain reflectometry monitoring of a deforming trackside lock-block retaining wall on the Ripley Slide in the Thompson River valley south of Ashcroft, British Columbia. Fiber optic strain data are evaluated in the context of results from global positioning system monitoring, field mapping and electrical resistivity tomographic survey across the landslide. This research aims to reduce the economic, environmental, health and public safety risks that landslides pose to the railway network operating in Canada and elsewhere.

Multi-parameter Monitoring of a Slow Moving Landslide: Ripley Slide, British Columbia, Canada

The Thompson River, south of Ashcroft, British Columbia, Canada is a particularly unique area where complex glacial geology, active geomorphic processes and critical infrastructure (both major national rail lines—CPR and CN) intersect with and are affected by a long history of slope instability. Well documented landslides along a +10 km stretch of the valley have been impacting infrastructure as far back as the 19th century. The Ripley landslide is a small slow moving translational failure that is known to have been active since 1951. It poses a hazard to the onsite infrastructure since both the CN and CPR tracks run adjacent to each other along the entire breadth of the landslide. The economic repercussions of severing both railways here would be pronounced. In response to this threat, an extensive suite of monitoring technology is now being applied that includes: traditional applications including permanent monitoring using GPS stations and piezometers; subsurface investigations involving drilling and shallow seismic surveys; the adoption of novel technologies such as linear fibre optic sensing and vertical subsurface ShapeAccelArray (SAA) inclinometry, the installation of corner reflectors for satellite based (RADARSAT-2) interferometry and the deployment of ground-based SAR and LiDAR for ongoing quantitative assessment. Herein we summarize the collective efforts associated with this extensive array of instrumentation and monitoring studies being undertaken to better manage this and other landslide hazards in Canada and elsewhere.

Rock fall hazard control along a section of railway based on quantified risk

ABSTRACT Rock falls represent a large percentage of landslide-related hazards reported by Canadian railways in mountainous terrain. A 54.7 km-long section of railway through the Canadian Cordillera is examined that experiences, on average, 18 rock falls each year. An approach for rock fall hazard management is developed based on quantified risk. The approach focuses on defining railway operation procedures (freight train operations and track maintenance) that comply with quantified risks. Weather-based criteria that define periods when rock falls are more likely to occur along the study area are examined. These criteria are used herein to reduce exposure to rock falls and reduce their consequences. Several freight train operation strategies are proposed that comply with a tolerable level of risk adopted in this study for illustrative purposes. The approach provides a simple, flexible and practical strategy for railway operations that can be regularly adopted by the operators, and that is based on a more comprehensive assessment of quantified risk.

Quantifying weather conditions for rock fall hazard management

Relationships between weather conditions and rock fall occurrences have been acknowledged in the past, but seldom have such relationships been quantified and published. Rock falls are frequent hazards along transportation corridors through mountainous terrain, and predicting hazardous rock fall periods based on weather conditions can enhance mitigation approaches. We investigate the relationship between weather conditions and rock fall occurrences along a railway section through the Canadian Cordillera. Monthly weather-rock fall trends suggest that the seasonal variation in rock fall frequency is associated with cycles of freezing and thawing during the winter months. The intensity of precipitation and freeze–thaw cycles for different time-windows was then compared against recorded rock falls on a case-by-case approach. We found that periods when 90% of rock falls occurred could be predicted by the 3-day antecedent precipitation and freeze–thaw cycles. Some rock falls not predicted by this 3-day antecedent approach occurred during the first two weeks of spring thaw. These findings are used to propose a rock fall hazard chart, based on readily available weather data, to aid railway operators in their decision-making regarding safe operations.

The 10-Mile Slide and Response of a Retaining Wall to Its Continuous Deformation

Open image in new window The 10-mile Slide has a volume of about 750,000 m3 and is sliding on a through-going shear surface at velocities up to 10 mm/day. Its importance is associated with the location of a highway and a railway line within its boundaries. Risks posed to the railway were managed through monitoring and running patrols in front of trains, and a pile retaining wall was installed immediately downslope from the tracks to prevent deformations caused by loosening of materials associated with the slope deformations and delay the retrogression of the landslide. Displacement measurements of the piles have monitored the response of the wall as the landslide retrogressed upslope from the railway track. This paper presents a brief description of the 10-mile Slide geologic context, its kinematics, mechanism, and evolution followed by a presentation of measured response of the retaining wall as the landside retrogressed.

LiDAR and Discrete Fracture Network Modeling for Rockslide Characterization and Analysis

On November 25, 2012, a rockslide occurred along the Canadian National Railway tracks, approximately 150 km northeast of Vancouver, Canada. The volume of the slide was approximately 53,000 m3. It caused four days of service disruption and the collapse of a rock shed protecting the tracks. This paper studies the triggering factors and the failure mechanism based on a combination of airborne 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 a railway protection structure (rock shed).