C. Derek Martin

RockFall analyst: A GIS extension for three-dimensional and spatially distributed rockfall hazard modeling

Geographic information system (GIS) modeling is used in combination with three-dimensional (3D) rockfall process modeling to assess rockfall hazards. A GIS extension, RockFall Analyst (RA), which is capable of effectively handling large amounts of geospatial information relative to rockfall behaviors, has been developed in ArcGIS using ArcObjects and C#. The 3D rockfall model considers dynamic processes on a cell plane basis. It uses inputs of distributed parameters in terms of raster and polygon features created in GIS. Two major components are included in RA: particle-based rockfall process modeling and geostatistics-based rockfall raster modeling. Rockfall process simulation results, 3D rockfall trajectories and their velocity features either for point seeders or polyline seeders are stored in 3D shape files. Distributed raster modeling, based on 3D rockfall trajectories and a spatial geostatistical technique, represents the distribution of spatial frequency, the flying and/or bouncing height, and the kinetic energy of falling rocks. A distribution of rockfall hazard can be created by taking these rockfall characteristics into account. A barrier analysis tool is also provided in RA to aid barrier design. An application of these modeling techniques to a case study is provided. The RA has been tested in ArcGIS 8.2, 8.3, 9.0 and 9.1.

Quantitative risk assessment of slope hazards along a section of railway in the Canadian Cordillera—a methodology considering the uncertainty in the results

Railway alignments through the Canadian Cordillera are constantly exposed to slope instabilities. Proactive mitigation strategies have been in place for a few decades now, and instability record keeping has been recognized as an important aspect of them. Such a proactive strategy has enhanced the industry’s capacity to manage slope risks, and some sections have been recognized as critical due to the frequency of instabilities. At these locations, quantification of the risks becomes necessary. Risk analysis requires knowledge of some variables for which statistical data are scarce or not available, and elicitation of subjective probabilities is needed. A limitation of such approaches lies in the uncertainty associated to those elicited probabilities. In this paper, a quantitative risk analysis is presented for a section of railway across the Canadian Cordillera. The analysis focused on the risk to life of the freight train crews working along this section. Upper and lower bounds were elicited to cope with the uncertainties associated with this approach. A Monte Carlo simulation technique was then applied to obtain the probability distribution of the estimated risks. The risk probability distribution suggests that the risk to life of the crews is below previously published evaluation criteria and within acceptable levels. The risk assessment approach proposed focuses on providing a measure of the uncertainty associated with the estimated risk and is capable of handling distributions that cover more than two orders of magnitude.

Movement triggers and mechanisms of two earth slides in the Thompson River Valley, British Columbia, Canada

Since the construction of the Canadian Pacific Railway and Canadian National Railway main rail lines in western Canada in 1885 and 1905, respectively, both companies have had to contend with 11 large, translational, retrogressive earth slides in the Thompson River Valley south of Ashcroft, British Columbia. The initiation of these slides is associated with the down cutting by the Thompson River through the Quaternary sediments in its valley. The slides move on two subhorizontal weak layers in a glaciolacustrine clay–silt unit within this Quaternary sediment sequence. Transient seepage and stability analyses were conducted for two sample slides, and the results were in agreement with inclinometer and piezometric data. It is concluded that the Thompson River triggers the movements in a drawdown mechanism and (or) erosion mechanism. The Thompson River affects the stability of these slides in three ways: (i) by changing the pore pressure on the rupture surface, (ii) by changing the supporting force on the toe...

Estimating the size and travel distance of Klapperhorn Mountain debris flows for risk analysis along railway, Canada

Debris flows occurring on Klapperhorn Mountain in the Yellowhead Pass in the Canadian Rocky Mountains pose a significant hazard to railway operations at the base of the mountain. The size (volume) and travel distance of these debris flows play an important role in assessing the risk to the railway. GIS analysis, airphoto interpretation together with field work were undertaken on two debris flows located at track mileage 54.0 and 54.3. Characteristics of these two debris flow events were analyzed, including debris flow path morphology and event behavior. Their sizes and travel distances were estimated using an empirical-statistical model (UBCDFLOW) under different initiation conditions. Their potential impact on the railway bridge was evaluated using a bridge blockage ratio.

Evaluating the Effect of Fiber Reinforcement on the Anisotropic Undrained Stiffness and Strength of Peat

AbstractThis paper presents the results of an investigation into the role of peat fibers in the development of anisotropic stiffness and strength within peat samples taken from below three Canadian National Railway embankments across Canada. These sites include two from northern Alberta on the Edson and Lac-La-Biche subdivisions and one from the Levis subdivision in southern Quebec. The peat samples were collected in Shelby tubes and were subjected to a program of consolidated undrained triaxial testing. These samples represented a wide variation in fiber content and degree of humification. The measured pore-pressure response during undrained loading indicated that the peat samples were undergoing an anisotropic elastic response to loading. This pore-pressure response was similar in the peat from all three sites, with an anisotropic pore-pressure parameter, a, of approximately 0.3. The stiffness and strength of the different peats were also similar, with an elastic modulus of approximately 1.7–2.2 MPa and...

Rockslide run-out prediction from distinct element analysis

The Checkerboard Creek Rock Slope is located 1.5 km upstream of the Revelstoke Dam, which impounds the Columbia River in British Columbia, Canada. A detailed investigation completed in 2004 indicated that 2 to 3 million m3 of a rock slope was moving toward the reservoir at rate of approximately 10 mm/year. There was concern that, if a portion of the slow-moving rockslide accelerated rapidly into the reservoir, the resultant wave could overtop the dam. Distinct element analyses were carried out using UDEC to assess potential rockslide run-out characteristics (time histories of rock volume, thickness and velocity). A Voronoi tessellation scheme was used to create a rock fabric that allowed the moving rock slope to disaggregate. The range of slide behaviours was investigated by varying the following four factors: (1) type and amount of damping used to simulate the coefficient of restitution and, thus, energy loss during run-out; (2) friction angle of contacts during movement; (3) reservoir effects; and (4) rock fragment sizes. The results from these analyses were used as input to a physical wave model study.

Behaviour of Weak Shales in Underground Environments

Predicting the ground response for tunnels in weak shales remains challenging. Predicting the ground response is challenged by difficulties in characterising the material, and our ability to predict deformations that are driven by coupled hydromechanical processes, when this material yields. The techniques that are used for characterising weak shales are reviewed, and three case histories are examined that demonstrate the behaviour of these weak rocks during tunnelling. A general framework is provided for assessing the squeezing potential for weak shales.

A three-dimensional equivalent continuum constitutive model for jointed rock masses containing up to three random joint sets

A three dimensional constitutive model is formulated for deformation analysis of jointed rock masses containing up to three joint sets with arbitrary spatial configurations. A representative elementary volume (REV) that represents the deformational response of the rock mass is defined and the constitutive relationships are developed based on superposition of deformations of the REV components. By representing the constitutive relationships in a tensorial form, the model is able to implement deformation anisotropy of jointed rock masses. The Mohr-Coulomb failure criterion with tension cut-off is used for the intact rock and the joint sets. The model is implemented in FLAC3D and the deformations and strength values calculated by the model are compared with the results from a 3DEC model and analytical solutions. The model results are in good agreement with those obtained from 3DEC.

Characterization of Locked Sand from Northeastern Alberta

A comprehensive experimental investigation was carried out on a lower Cretaceous friable intact sand formation retrieved from northeastern Alberta. Index tests, microstructural observations, and mineralogical composition analyses were carried out to confirm that this formation fits into the locked sand category. The significance of the local strain measurements in revealing salient deformation characteristics of this formation was explored under uniaxial stress conditions. The test results showed that the characteristics of this formation are in keeping with the characteristics of locked sands. The intimacy between the grains stems from authigentic quartz creating interlocking rather than cementation. The results also revealed that local axial and lateral strain measurements are essential for proper behavioral characterization and failure mechanism interpretation of locked sands. The interlocked fabric results in an exceptionally high uniaxial strength and elastic axial stiffness. The disruption of the interlocking is achieved through the lateral expansion of the sample and formation of dilation bands.

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.