Publications

2017

  • View abstract

    The Colorado Department of Transportation (CDOT) has recently implemented a Risk-Based Transportation Asset Management Plan (RB TAMP) that incorporates geotechnical assets and hazards. CDOT’s RB TAMP includes an ancillary wall structures program that includes all earth retaining structures, and a geohazards management program which is used to manage multiple hazards related to slopes, embankments, and roadway subgrade. The RB TAMP states multiple performance goals to be achieved, including safety, infrastructure condition, reliability, congestion, and maintenance, and the state will measure and report progress in these areas. Natural hazards, physical failures, external agency impacts and operational risks are risk types that present threats to CDOT’s achievement of their goals. The way these risks act on assets to impact performance goals can be visualized in a cubic form, and this allows for recognition of how many elements of risk there are, for making explicit decisions on which risks to address and how, and for communicating these decisions to others. Risk analysis at CDOT includes both qualitative and quantitative approaches in accordance with data availability. The quantitative estimate of risk is expressed in terms of exposure cost for all assets, risk types and performance goals and then used by CDOT subject matter experts for project selection and planning.

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    Mountain environments, home to about 12% of the global population and covering nearly a quarter of the global land surface, create hazardous conditions for various infrastructures. The economic and ecologic importance of these environments for tourism, transportation, hydropower generation, or natural resource extraction requires that direct and indirect interactions between infrastructures and geohazards be evaluated. Construction of infrastructure in mountain permafrost environments can change the ground thermal regime, affect gravity-driven processes, impact the strength of ice-rich foundations, or result in permafrost aggradation via natural convection. The severity of impact, and whether permafrost will degrade or aggrade in response to the construction, is a function of numerous parameters including climate change, which needs to be considered when evaluating the changes in existing or formation of new geohazards. The main challenge relates to the uncertainties associated with the projections of medium- (decadal) and long-term (century-scale) climate change. A fundamental understanding of the various processes at play and a good knowledge of the foundation conditions is required to ascertain that infrastructure in permafrost environment functions as intended. Many of the tools required for identifying geohazards in the periglacial and appropriate risk management strategies are already available.

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    The use of computer models to determine rock fall hazards is increasingly common, with increasingly complex models being developed. In most practical applications, slopes potentially affected by rock falls are characterized in general terms only, thus a simpler model is desirable to reduce the parameter uncertainty. The model presented here utilizes a lumped-mass representation of the rocks. Key features are the stochastic roughness angle to represent contact geometry variability, hyperbolic restitution factors, and a stochastic shape factor, which have been developed considering impact mechanics theory. Together, these features can yield realistic results for linear and angular velocity, bounce height, runout distance, and normal restitution factors greater than one while still being easy to calibrate. The model calibration has been carried out using detailed, full-scale experiments from a talus slope in France, a hard rock quarry in Austria, and a weak bedrock and talus slope in Japan. An observed rock fall event in British Columbia was modeled as a pseudoforward analysis to demonstrate the model validity. The usefulness of the model as a design tool has been demonstrated by using the simulation results as inputs for a hypothetical barrier design application, and calculating the reliability of the design values.

     

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    Rockfalls impact the safety and capacity of railway operation, particularly in mountainous terrain such as that of interior British Columbia. Therefore, there is interest in identifying natural slopes along a railway corridor which may be prone to rockfall events. Though the triggers and mechanisms, which dictate the size, frequency and reach of rockfall events, vary over space and time, there are kinematic and geological properties which can be used to characterize the slope with regard to its rockfall susceptibility. This paper explores these properties and determines how they can be efficiently identified within remotely sensed terrain data over large areas. State of the art remote sensing techniques for 3D data collection and analysis and new tools and applications at various sites along the CN Rail corridor in the Fraser River valley are demonstrated. We discuss the application of these new tools to identifying evidence of previous rockfalls and geological structures which may act as a rockfall source.

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    Historical heavy use of chlorinated solvents in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater in North America and worldwide. As a result, remediation of chlorinated solvents is required at many sites. For source zone treatment, common remediation strategies include in-situ chemical oxidation (ISCO) using potassium or sodium permanganate, and the enhancement of biodegradation by primary substrate addition. It is well known that these remediation methods tend to generate gas (carbon dioxide (CO2) in the case of ISCO using permanganate, CO2 and methane (CH4) in the case of bioremediation). Vigorous gas generation in the presence of chlorinated solvents, which are categorized as volatile organic contaminants (VOCs), may cause gas exsolution, ebullition and stripping of the contaminants from the treatment zone. This process may lead to unintentional ‘compartment transfer’, whereby VOCs are transported away from the contaminated zone into overlying clean sediments and into the vadose zone. To this extent, benchtop column experiments were conducted to quantify the effect of gas generation during remediation of the common chlorinated solvent trichloroethylene (TCE/C2Cl3H). Both ISCO and enhanced bioremediation were considered as treatment methods. Results show that gas exsolution and ebullition occurs for both remediation technologies. Facilitated by ebullition, TCE was transported from the source zone into overlying clean groundwater and was subsequently released into the column headspace. For the case of enhanced bioremediation, the intermediate degradation product vinyl chloride (VC) was also stripped from the treatment zone. The concentrations measured in the headspace of the columns (TCE ∼ 300 ppm in the ISCO column, TCE ∼ 500 ppm and VC ∼ 1380 ppm in the bioremediation column) indicate that substantial transfer of VOCs to the vadose zone is possible. These findings provide direct evidence for the unintended spreading of contaminants as a result of remediation efforts, which can, under some circumstances, result in enhanced risks for soil vapour intrusion.

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    The recent assessment of the Mitchell Creek Landslide (MCL) in northern British Columbia is a good case history of engineering geomorphological analysis of a large landslide. It was completed using historic aerial photographs, with approximately 20-year time intervals dating back to the mid-twentieth century and field investigations completed between 2008 and 2014. The large bedrock slide initiated between 1956 and 1972 and continues to experience ongoing annual movements. Significant glacial downwasting and retreat has been observed in the photographic record, and it is hypothesized that alpine glaciation has contributed to development of the MCL. This paper documents four aspects of the engineering geomorphological assessment completed at the MCL: (i) topographic evolution, (ii) slope morphology, (iii) deformation features, and (iv) displacement behavior. Four distinct geomorphic zones have been defined at the MCL based on these analyses, controlled by different failure mechanisms. The extents of these zones have changed little over the documented history of the landslide, and rates of movement estimated from aerial photography have been consistent over the last 60 years. Retreat of the Mitchell Valley Glacier appears to have played an important role in landslide initiation, as the ice mass receded the kinematic freedom of the slope increased. This study of the initiation and development of the MCL demonstrates the capabilities of a multi-faceted approach to engineering geomorphology. The combination of historical aerial photographs with digital photogrammetric modeling and point cloud analysis techniques, and geomorphological mapping, allows for development of a robust understanding of landslide behavior.

  • View abstract

    The recent assessment of the Mitchell Creek Landslide (MCL) in northern British Columbia is a good case history of engineering geomorphological analysis of a large landslide. It was completed using historic aerial photographs, with approximately 20-year time intervals dating back to the mid-twentieth century and field investigations completed between 2008 and 2014. The large bedrock slide initiated between 1956 and 1972 and continues to experience ongoing annual movements. Significant glacial downwasting and retreat has been observed in the photographic record, and it is hypothesized that alpine glaciation has contributed to development of the MCL. This paper documents four aspects of the engineering geomorphological assessment completed at the MCL: (i) topographic evolution, (ii) slope morphology, (iii) deformation features, and (iv) displacement behavior. Four distinct geomorphic zones have been defined at the MCL based on these analyses, controlled by different failure mechanisms. The extents of these zones have changed little over the documented history of the landslide, and rates of movement estimated from aerial photography have been consistent over the last 60 years. Retreat of the Mitchell Valley Glacier appears to have played an important role in landslide initiation, as the ice mass receded the kinematic freedom of the slope increased. This study of the initiation and development of the MCL demonstrates the capabilities of a multi-faceted approach to engineering geomorphology. The combination of historical aerial photographs with digital photogrammetric modeling and point cloud analysis techniques, and geomorphological mapping, allows for development of a robust understanding of landslide behavior.

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    This research presents a case study of the use of specific energy measurements to map and model pit-scale faults in the Granite Pit at Gibraltar Mine, an open pit metal mine in British Columbia, Canada. Specific energy data were collected during drilling of over 100,000 blast holes. Specific energy is affected not only by the geomechanical properties of the rock being drilled, but also by drilling parameters, equipment wear, and drilling depth. The influence of these factors is partly mitigated by adjusting the dataset for drilling depth and applying a bilateral smoothing filter. The specific energy dataset is compared to known pit-scale faults, UAV photogrammetry, LiDAR models, and rock mass data from geotechnical drilling. Planar concentrations of low specific energy data are seen to correspond to the location of major faults. This is evidenced further by showing that specific energy increases with distance from faults, similar to rock mass quality.

Davidson, S.L. and Eaton, B.C. 2017. A stochastic model of channel width adjustment, Does hydrology influence channel size and effective discharge? Canadian Geophysical Union – Canadian Society of Agricultural and Forest Meteorology Joint Annual Scientific Meeting, Vancouver, BC, 28-31 May 2018. Oral presentation.

Davidson, S.L. and Roberge, L. 2017. Incorporating river mechanics into geohazard management, A simple model for quantifying bank erosion. Canadian Geophysical Union – Canadian Society of Agricultural and Forest Meteorology Joint Annual Scientific Meeting, Vancouver, BC, 28-31 May 2018. Oral presentation.

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    We compared median runoff (R) and precipitation (P) relationships over 25 years from 20 mesoscale (50 to 5,000 km2) catchments on the Boreal Plains, Alberta, Canada, to understand controls on water sink and source dynamics in water‐limited, low‐relief northern environments. Long‐term catchment R and runoff efficiency (RP−1) were low and varied spatially by over an order of magnitude (3 to 119 mm/year, 1 to 27%). Intercatchment differences were not associated with small variations in climate. The partitioning of P into evapotranspiration (ET) and R instead reflected the interplay between underlying glacial deposit texture, overlying soil‐vegetation land cover, and regional slope. Correlation and principal component analyses results show that peatland‐swamp wetlands were the major source areas of water. The lowest estimates of median annual catchment ET (321 to 395 mm) and greatest R (60 to 119 mm, 13 to 27% of P) were observed in low‐relief, peatland‐swamp dominated catchments, within both fine‐textured clay‐plain and coarse‐textured glacial deposits. In contrast, open‐water wetlands and deciduous‐mixedwood forest land covers acted as water sinks, and less catchment R was observed with increases in proportional coverage of these land covers. In catchments dominated by hummocky moraines, long‐term runoff was restricted to 10 mm/year, or 2% of P. This reflects the poor surface‐drainage networks and slightly greater regional slope of the fine‐textured glacial deposit, coupled with the large soil‐water and depression storage and higher actual ET of associated shallow open‐water marsh wetland and deciduous‐forest land covers. This intercatchment study enhances current conceptual frameworks for predicting water yield in the Boreal Plains based on the sink and source functions of glacial landforms and soil‐vegetation land covers. It offers the capability within this hydro‐geoclimatic region to design reclaimed catchments with desired hydrological functionality and associated tolerances to climate or land‐use changes and inform land management decisions based on effective catchment‐scale conceptual understanding.

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    Northern peatlands are a vital component of the global carbon cycle, containing large stores of soil organic carbon and acting as a long‐term carbon sink. Moss productivity is an important factor in determining whether these wetlands will retain this function under future climatic conditions. Research on unsaturated water flow in peatlands, which controls moss productivity during periods of evaporative stress, has focused on relatively deep bog systems. However, shallower peatlands and marginal connective wetlands can be essential components of many landscape mosaics. In order to better understand factors influencing moss productivity, water balance simulations using HYDRUS‐1D were run for different soil profile depths, compositions, and antecedent moisture conditions. Our results demonstrate a bimodal distribution of peatland realizations, either primarily conserving water by limiting evapotranspiration or maximizing moss productivity. For sustained periods of evaporative stress, both deep water storage and a shallow initial water table delay the onset of high vegetative stress, thus maximizing moss productivity. A total depth of sand and peat of 0.8 m is identified as the threshold above which increasing peat depth has no effect on changing vegetative stress response. In contrast, wetlands with shallow peat deposits (less than 0.5 m thick) are least able to buffer prolonged periods of evaporation due to limited labile water storage and will thus quickly experience vegetative stress and so limit evaporation and conserve water. With a predicted increase in the frequency and size of rain events in continental North America, the moss productivity of shallow wetland systems may increase, but also greater moisture availability will increase the likelihood they remain as wetlands in a changing climate.

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    Experiments using a 1∶30 scale physical model show that channel degradation on alluvial fans is dominated by lateral channel migration rather than vertical incision. The results are used to estimate the exposure probability during single flood events with peak flows up to twice the formative flow, considering both the burial depth beneath the channel bed and the setback from the channel banks. For the largest flows modeled, the exposure probability fell below the detection limits for this analysis when the burial depth was greater than approximately 3.6 times the mean flow depth, and the lateral setback distance was greater than approximately 0.9 times the mean flow width for the formative flow. The minimum depth-of-cover criterion accounts for the worst-case occurrence of net bed degradation during a single flood event, but does not consider the vertical degradation that could occur in channels because of knickpoint development and migration, or in channels with engineered banks that prevent channel width adjustments; they also do not consider the potential effects of debris flows. These hazards are driven by different processes and require different analyses to evaluate the potential exposure risk. Because the experiments evaluated the effects of single flood events, the results do not account for shifting channel position over time, and they are intended to guide monitoring of channel behavior for existing infrastructure. The results also can be used to guide infrastructure design, but in this case the design will need to consider the cumulative effect of channel migration and avulsion over the design life span of the infrastructure.

Gauthier, D. 2017. Probabilistic rock fall monitoring at the network scale: finding the next one. Transportation Research Board Annual Meeting, Washington, DC, 8-12 January 2017. Presentation.

  • View abstract

    Recent advances in three-dimensional remote monitoring of steep rock slopes have made it possible to consistently detect both past and incipient rockfalls with high precision. Both large and small bulk deformations of discrete rock blocks are detectable using these techniques, both of which may represent precursors or indicators of even larger incipient rockfalls. The 'change detection' analysis of sequential terrestrial LiDAR and oblique aerial structure-from-motion photogrammetry models of steep rock slopes have produced impressive results on the single slope-scale. However, there remain significant limitations and uncertainties in deploying these techniques beyond a single slope, such as the massive quantity of data, the effort in collecting and processing models at high resolution, and the effort and skill required to manually interpret the results in relation to rockfall hazard. To date, these and other factors have impeded the widespread deployment of the methods. To that end, both the Colorado DoT and the Canadian Railway Ground Hazard Research Program have independently engaged in ambitious programs to extend these slope-scale successes up to the network scale, covering hundreds of miles (or more) of linear transportation corridors. In this paper, we review the state-of-the-art in three-dimensional slope monitoring and rockfall hazard assessment for transportation corridors, the results and progress of recent corridor-scale pilot studies in Colorado and Canada, and we outline a framework to efficiently and effectively extend these advances to the network scale. We conclude with a discussion of the current knowledge gaps in this area which would benefit from further research and development.

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    The Dry Andean Region (20˚S to 40˚S) is the most arid part of the Andean Cordillera. Snowmelt and glacier runoff from this high-altitude region is an important source and temporal regulator of water supporting agricultural, human and environmental needs in the semi-arid lowlands. To understand the influence of a changing climate on this important source of water, the MODIS Terra eight-day 500 metre maximum snow cover extent was used to examine recent trends in snow cover within this region between 2000 and 2016. The annual maximum, mean and minimum snow cover were calculated to examine the annual range of snow cover as well as temporal trends in the statistics. A Mann-Kendall analysis was used to test for the significance of the trends in the three annual snow cover statistics and compare them against large scale climate oscillations, e.g. ENSO. Furthermore, the magnitude and direction of these trends in the annual snow cover statistics were analyzed using linear regressions and thus estimate their future behaviour. The snow cover season was also used to examine the duration of the year with persistent snow along with the start and end dates of the snow cover season. The start and end of the snow cover season was determined by selecting the period during which the spatial presence of snow exceeded a pre-defined threshold. Its duration was then determined by the difference between the start and end dates, and Mann-Kendall analysis was used to test for trends. The analysis was applied to the entire Dry Andean region (20˚S to 40˚S) as watersheds in both Chile and Argentina to evaluate regional differences. Our presentation will report on our findings including statistically significant trends.

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    The thermal regimes of alpine streams remain understudied and have important implications for cold-water fish habitat, which is expected to decline due to climatic warming. Previous research has focused on the effects of distributed energy fluxes and meltwater from snowpacks and glaciers on the temperature of mountain streams. This study presents the effects of the groundwater spring discharge from an inactive rock glacier containing little ground ice on the temperature of an alpine stream. Rock glaciers are coarse blocky landforms that are ubiquitous in alpine environments and typically exhibit low groundwater discharge temperatures and resilience to climatic warming. Water temperature data indicate that the rock glacier spring cools the stream by an average of 3 °C during July and August and reduces maximum daily temperatures by an average of 5 °C during the peak temperature period of the first two weeks in August, producing a cold-water refuge downstream of the spring. The distributed stream surface and streambed energy fluxes are calculated for the reach along the toe of the rock glacier, and solar radiation dominates the distributed stream energy budget. The lateral advective heat flux generated by the rock glacier spring is compared to the distributed energy fluxes over the study reach, and the spring advective heat flux is the dominant control on stream temperature at the reach scale. This study highlights the potential for coarse blocky landforms to generate climatically resilient cold-water refuges in alpine streams.

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    Ten Mile Slide is an area of active ground movement located in the Fraser River canyon northeast of Lillooet, British Columbia, Canada. It is crossed by Highway 99 and the Canadian National railway and has been the subject of several previous geotechnical studies, site investigations, and movement mitigation efforts. It occurs within the toe of Tunnel Earthflow, a much larger, inactive post-glacial landslide deposit. Ten Mile Slide initiated around 1984 as local instability on a steep bench scarp facing the Fraser River below Highway 99, and has since retrogressed in step-wise fashion approximately 265 meters up the slope. Historical monitoring and remote sensing data show that the landslide has moved at average rates from 1.1 m to 3.7 m per year. Sliding movement is translational, occurring along a narrow, roughly planar shear surface located near the base of the Tunnel Earthflow deposit. Slope stability back-analyses indicate that the residual friction angle of this basal shear surface is approximately 21°. The mobilized body of Ten Mile Slide is mainly dry, has higher strength than the basal shear surface, and behaves as a relatively stiff and cohesive mass. Previous efforts to stabilize the highway and railway have only mitigated landslide movements temporarily. This paper presents a detailed study of Ten Mile Slide’s geologic environment, style of movement, evolution over time, and the implications these factors have on the engineering design of a long-term stabilization solution at the highway.

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    The District of North Vancouver (DNV) has a long history of managing geohazards. Starting in the 1990s, and updated approximately every 10 years, DNV has retained geotechnical and geoscientist consultants to assess debris geohazard (i.e., debris floods and debris flows) risks and make recommendations for reducing risk to tolerable levels. In 2015-2016, we completed comprehensive flood, debris flood- and debris-flow risk assessments for 35 steep creeks within the District using a variety of custom-tailored methods described in this contribution. While most creeks’ headwaters are in forested and largely undeveloped terrain, the lower reaches flow through municipal areas containing over 20,000 buildings and a network of roads, utilities, and stormwater management infrastructure. The objectives of the assessment were to assess debris geohazards including their frequency, magnitude, extent, and potential to result in blockage and overflow of DNV stormwater management infrastructure; estimate the risk posed by these hazards to buildings and persons within buildings, prioritize locations for risk reduction planning; and develop risk control options and costs. Based on the results of the assessment, DNV staff are developing a 10-year work plan that will be integrated with the District’s asset management, GIS-based inspection program, climate change adaptation and hazard mitigation plans. The work presented herein is an example of a pro-active science-based creek management program aiming to optimize funds for public safety and economic risk reduction.

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    In this paper we present the first results from Coherent Points Analyses and Differential Stacking of RADARSAT-2 InSAR persistent scatterer interferograms covering a portion of the Thompson River valley, south of Ashcroft in British Columbia Canada. Surface displacements amounting to less than 5 cm/year are detected on landslides that are crossed by national railway infrastructure (train tracks and lock-block retaining walls). Our study shows that many landslides in the Thompson River valley have zones of displacement that are more active than others. For the portions of the North Slide, South Slide and Barnard Slide, zones of active displacement landslide can be resolved within the InSAR data acquired between 2013 and 2016. In contrast, both the Ripley Landslide and Red Hill Slide show marked variations in displacement rates related to seasonal changes in river stage and groundwater level, and compound translational-rotational sliding of coherent blocks of sediment. InSAR techniques effectively capture the surface movement detected by GPS stations, ground-based LiDAR, borehole piezometers and fibre optic installations at the Ripley Landslide test site. This successful application of Coherent Points Analysis and Differential Stacking of persistent scatterer interferograms suggests both techniques are suitable for monitoring unstable terrain in other remote settings where infrastructure, natural resources, the environment, local communities and public safety are at risk.

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    A destructive debris flood occurred between 19 and 21 June 2013 on Cougar Creek, located in Canmore, Alberta. Cougar Creek fan is likely the most densely developed alluvial fan in Canada. While no lives were lost, the event resulted in approximately $40 M of damage and closed both the Trans-Canada Highway (Highway 1) and the Canadian Pacific Railway line for a period of several days. The debris flood triggered a comprehensive hazard assessment which is the focus of this paper. Debris-flood frequencies and magnitudes are determined by combining several quantitative methods including photogrammetry, dendrochronology, radiometric dating, test pit logging, empirical relationships between rainfall volumes and sediment volumes, and landslide dam outburst flood modeling. The data analysis suggests that three distinct process types act in the watershed. The most frequent process is normal or “clearwater” floods. Less frequent but more damaging are debris floods during which excessive amounts of bedload are transported on the fan, typically associated with rapid and extensive bank erosion and channel infilling and widening. The third and most destructive process is interpreted to be landslide dam outbreak floods. This event type is estimated to occur at return periods exceeding 300 years. Using a cumulative magnitude frequency technique, the data for conventional debris floods were plotted up to the 100–300s year return period. A peak-over-threshold approach was used for landslide dam outbreak floods occurring at return periods exceeding 300 years, as not all such events were identified during test trenching. Hydrographs for 6 return period classes were approximated by using the estimated peak discharges and fitting the hydrograph shape to integrate to the debris flood volumes as determined from the frequency-magnitude relationship. The fan volume was calculated and compared with the integrated frequency-magnitude curve to check of the validity of the latter. A reasonable match was accomplished, verifying the overall relationship. The findings from this work were later used as input to a risk assessment seeking to quantify risk to loss of life and economic losses. The risk assessment then formed the basis for design of debris-flood mitigation structures.

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    Boreal peatlands may be vulnerable to projected changes in the wildfire regime under future climates. Extreme drying during the sensitive postfire period may exceed peatland ecohydrological resilience, triggering long-term degradation of these globally significant carbon stocks. Despite these concerns, we show low peatland evapotranspiration at both the plot- and landscape-scale postfire, in water-limited peatlands dominated by feather moss that are ubiquitous across continental western Canada. Low postfire evapotranspiration enhances the resilience of carbon stocks in such peatlands to wildfire disturbance and reinforces their function as a regional source of water. Near-surface water repellency may provide an important, previously unexplored, regulator of peatland evapotranspiration that can induce low evapotranspiration in the initial postfire years by restricting the supply of water to the peat surface.

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    The performances of ten graphical identification methods to estimate preconsolidation pressure are evaluated. The evaluation is based on constant rate of strain (CRS) consolidation tests conducted on undisturbed Champlain Sea clay samples obtained using a Laval sampler. The methods are first evaluated for accuracy based on known maximum past pressure in unloading/reloading test cycles. They are then applied to the initial loading stages for comparison. To facilitate the interpretation of the preconsolidation pressure and reduce its subjectivity, analytical solutions based on distinctive points on the CRS curve are developed for the ten graphical identification methods. Finally, a series of correction equations are proposed based on the results of applying the different graphical methods to the reloading stages. The bilogarithmic methods are found to be the most accurate, and different bilogarithmic methods give identical results. Other bilinear methods and the Pacheco Silva method also give highly accurate results.

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    We present an automated terrestrial laser scanning (ATLS) system with automatic near-real-time change detection processing. The ATLS system was tested on the Séchilienne landslide in France for a 6-week period with data collected at 30 min intervals. The purpose of developing the system was to fill the gap of high-temporal-resolution TLS monitoring studies of earth surface processes and to offer a cost-effective, light, portable alternative to ground-based interferometric synthetic aperture radar (GB-InSAR) deformation monitoring. During the study, we detected the flux of talus, displacement of the landslide and pre-failure deformation of discrete rockfall events. Additionally, we found the ATLS system to be an effective tool in monitoring landslide and rockfall processes despite missing points due to poor atmospheric conditions or rainfall. Furthermore, such a system has the potential to help us better understand a wide variety of slope processes at high levels of temporal detail.

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    Rockfalls represent significant risks to safe and efficient use of transportation corridors. In this paper we address the management of rockfall risk through baseline remote monitoring of susceptible slopes (every 2-4 months) along a transportation corridor along the Fraser River Valley in western Canada with a terrestrial laser scanner and supporting remote sensing technologies. This includes identifying potential rockfall source zones based on incipient signs of failure, tracking kinematics in 3D to better understand the mechanism of failure, estimating potential failure volumes based on bounding joint structure and transmitting this information to the railway operator for an assessment of risk. We demonstrate our approach for one case along the line where we identified several potential failures ranging in volume from 48 m3 to 4200 m3. Our projections of the location of failures were successful, in that volume projections were within 10-55%, and the anticipated kinematics and failure mechanism were consistent with the assessment of post failure rockfall scar geometries. Accurate volume and kinematics estimates are important for the assessment of hazard, risk and the planning of risk mitigation options. In general, this approach can be used to better manage risk from rockfall hazard in communities, transportation corridors or other infrastructure.

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    Ten Mile Slide, also known as Fountain Slide, is an active landslide in southwestern British Columbia that is crossed by BC Highway 99 and Canadian National (CN) Railway. Currently, the BC Ministry of Transportation and Infrastructure (MoTI) is pursuing measures to manage landslide deformations along a 200 m stretch of Highway 99 through structural support. To support this work, 3-dimensional (3D) surficial monitoring at the site is being conducted by analyzing Terrestrial Laser Scanning (TLS) data. TLS data are collected bi-weekly in snow free conditions from the opposite side of the Fraser River, approximately 500 m away from Highway 99. Each TLS scan is aligned to the initial baseline dataset and evaluated for 3D differential change. The accuracy of the datasets and their alignment to the baseline dataset range between 0.02 m and 0.03 m facilitating a limit of detectable change between 0.04 m and 0.06 m. Individual blocks within the dataset are tracked and the velocity of movements are evaluated in conjunction with precipitation data recorded on site. The TLS data enables surficial movement to be tracked across the entire active landslide facilitating assessment of change in regions inaccessible to traditional surveying methods. The TLS analysis further enables the identification of discrete regions within the slide mass displacing at varying rates providing supplementary information on the behavior of the slide mass at a higher temporal resolution than was previously available; this information aids in the planning of the mitigation efforts.

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    Advances in the field of 3-dimensional (3D) remote sensing data collection and processing techniques over the past ten years have fundamentally changed how engineers and geoscientists interpret surface deformation and correlate movement with geological models. Researchers and practitioners have developed and implemented sophisticated analytical methods using LiDAR and photogrammetry data to aid in the understanding of landslide dynamics, regions and rates of change, direction of motion, and the ability to forecast rock fall source zones and volumes. Integrating 3D analysis alongside traditional subsurface borehole, field mapping, and instrumentation data is enabling engineers and geoscientists to understand geomorphic processes at a previously unattained level of granularity. This deeper understanding leads to an increased ability to develop practical solutions in challenging conditions. This paper outlines a case study that demonstrates the use of terrestrial and airborne LiDAR data to aid in the understanding of a geologically complicated landslide that poses significant consequence to multiple stakeholders. The landslide is traversed by a provincial highway and a CN railway line with variable thresholds for tolerable slide movement and disturbance to their operations. The work in this case study was completed through a collaboration between BGC Engineering and Queen’s University for the British Columbia Ministry of Transportation and Infrastructure. The importance of involving researchers in applied geohazard assessment and management work is discussed in detail.

Lau, C.A., Ward, B.C., Jakob, M., and Schwarz, C. 2017. Morphological influence and recognition of channel scour hazards on fans in British Columbia. Canadian Geophysical Union – Canadian Society of Agricultural and Forest Meteorology Joint Annual Scientific Meeting, Vancouver, BC, 28-31 May 2018. Oral presentation.

Lau, C.A., Zei, C., Clague, J., Ward, B.C., Giardino, M., Vogt, N., Menounos, B., Wong, H., and Westin, A. 2017. Effects of landslide and flood-induced sediment pulses on the geomorphology of the Upper Lillooet River Valley. Canadian Geophysical Union – Canadian Society of Agricultural and Forest Meteorology Joint Annual Scientific Meeting, Vancouver, BC, 28-31 May 2018. Oral presentation.

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    In the Boreal Plain of Canada, the margins of peatland ecosystems that regulate solute and nutrient fluxes between peatlands and adjacent mineral uplands are prone to deep peat burning. Whether post-fire carbon accumulation is able to offset large carbon losses associated with the deep burning at peatland margins is unknown. For this reason, we examined how post-fire hydrological conditions (i.e. water table depth and periodicity, soil tension, and surface moisture content) and depth of burn were associated with moss recolonization at the peatland margins of three sites. We then interpreted these findings using a hydrogeological systems approach, given the importance of groundwater in determining conditions in the soil-plant-atmosphere continuum in peatlands. Peatland margins dominated by local groundwater flow from adjacent peatland middles were characterized by dynamic hydrological conditions that, when coupled with lowered peatland margin surface elevations due to deep burning, produced two common hydrological states: 1) flooding during wet periods and 2) rapid water table declines during dry periods. These dynamic hydrological states were unfavorable to peatland moss recolonization and bryophytes typical of post-fire recovery in mineral uplands became established. In contrast, at a peatland margin where post-fire hydrological conditions were moderated by larger-scale groundwater flow, flooding and rapid water table declines were infrequent and, subsequently, greater peatland-dwelling moss recolonization was observed. We argue that peatland margins poorly connected to larger-scale groundwater flow are not only prone to deep burning but also lags in post-fire moss recovery. Consequently, an associated reduction in post-fire peat accumulation may occur and negatively affect the net carbon sink status and ecohydrological and biogeochemical function of these peatlands.

McDougall, S., Jalil, N., Aaron, J., Mitchell, A., Whittall, J., McClarty, D., and Brideau, M.-A. 2017. Development of an online database and empirical hazard mapping tool for rock avalanche runout estimation. Canadian Geophysical Union – Canadian Society of Agricultural and Forest Meteorology Joint Annual Scientific Meeting, Vancouver, BC, 28-31 May 2018. Poster presentation.

  • View abstract

    "This tailings pours like chocolate milk, but when you add flocculant, it becomes more like blueberry pie filling." We often compare the unusual geotechnical properties of soft tailings to common foods. Soft tailings' shear strengths are much lower than most geotechnical people are accustomed—indeed many tailings are better described using fluid mechanics than soil mechanics. So people describe the consistency (mainly strength, but also sensitivity and density) of soft tailings using informal comparisons to foods such as chocolate milk, yogurt, porridge, cottage cheese, and peanut butter. Lacking is an accessible reference that provides a more direct, more authoritative comparison of tailings and foods. So with two hours at the grocery store, two days of hard work in the University of Alberta laboratory, and two weeks of crunching the data and writing it up for a recent oil sands tailings publication, we're pleased to share the results with a wider geotechnical audience.

  • View abstract

    As technology continues to advance, unmanned aerial vehicles (UAVs) have become a viable method to collect geometric data for geotechnical analysis, due to their ability to capture high resolution data at inaccessible sites, combined with increasing affordability and ease of use. UAVs can be divided into three general classes, based on cost and operational considerations. The use of photographs taken from a UAV to supplement terrestrial photogrammetry for a complex, steep slope in White Canyon, British Columbia, is discussed. The development of a detailed geometry model is possible using Structure from Motion (SfM), without ground control points. A significant edge effect occurs at the locations where the UAV and terrestrial DSLR photographs overlapped. This prevents an apparently seamless 3D model from being built, affecting change detection. Additional research is recommended to develop and refine the use of UAVs in slope stability analysis, specifically in areas not visible from terrestrial vantage points.

  • View abstract

    In this experimental study, granular material is released down slope to investigate landslide-generated waves. Starting with a known volume and initial position of the landslide source, detailed data are obtained on the velocity and thickness of the granular flow, the shape and location of the submarine landslide deposit, the amplitude and shape of the near-field wave, the far-field wave evolution, and the wave runup elevation on a smooth impermeable slope. The experiments are performed on a 6.7 m long 30° slope on which gravity accelerates the landslides into a 2.1 m wide and 33.0 m long wave flume that terminates with a 27° runup ramp. For a fixed landslide volume of 0.34 m3, tests are conducted in a range of still water depths from 0.05 to 0.50 m. Observations from high-speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material, and that only a portion of the landslide (termed the "effective mass") is engaged in activating the leading wave. The wave behavior is highly dependent on the water depth relative to the size of the landslide. In deeper water, the near-field wave behaves as a stable solitary-like wave, while in shallower water, the wave behaves as a breaking dissipative bore. Overall, the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near-field wave amplitude, the far-field amplitude, and the runup of tsunamis generated by granular landslides.

  • View abstract

    The use of computer models to determine rock fall hazards is increasingly common, with increasingly complex models being developed. In most practical applications, slopes potentially affected by rock falls are characterized in general terms only, thus a simpler model is desirable to reduce the parameter uncertainty. The model presented here utilizes a lumped-mass representation of the rocks. Key features are the stochastic roughness angle to represent contact geometry variability, hyperbolic restitution factors, and a stochastic shape factor, which have been developed considering impact mechanics theory. Together, these features can yield realistic results for linear and angular velocity, bounce height, runout distance, and normal restitution factors greater than one while still being easy to calibrate. The model calibration has been carried out using detailed, full-scale experiments from a talus slope in France, a hard rock quarry in Austria, and a weak bedrock and talus slope in Japan. An observed rock fall event in British Columbia was modeled as a pseudoforward analysis to demonstrate the model validity. The usefulness of the model as a design tool has been demonstrated by using the simulation results as inputs for a hypothetical barrier design application, and calculating the reliability of the design values.

  • View abstract

    Steep creek hazards such as debris flows and debris floods pose considerable risks to mountain communities and infrastructure. In Europe and Japan, centuries of experience in steep creek hazard mitigation have produced substantial practical design knowledge. By comparison, Canadian professionals have limited experience with engineered debris-flow and debris-flood risk management. To close the knowledge gap, we present a design approach that aims to improve the state of practice in Canada, drawing from local and international experience.

  • View abstract

    ​Various methods are applied by landslide professionals in consulting, government and industry to assess and communicate landslide safety. These include factor of safety calculations, designation and delineation of slope setback distances, estimates of hazard probability or encounter probability, and semi-quantitative and fully quantitative estimates of risk of loss of life. Because the sudden and often unexpected occurrence of very rapid to extremely rapid landslides can result in life loss, and because a consensus on appropriate risk tolerance criteria is emerging in western Canada, quantitative risk assessment (QRA) is gaining popularity amongst regulators and landslide professionals to assess and communicate levels of landslide safety where residential development and other infrastructure are exposed to these hazards. Use of QRAs requires development of appropriate methods for landslide inventories, magnitude, frequency, mobility and intensity estimates of past and future landslides as well as vulnerability estimates of people and infrastructure at risk. It also requires access to landslide risk tolerance criteria to contextualize risk estimates and guide communication and risk management decisions.

Sala, Z., Hutchinson, D.J., and Ondercin, M. 2017. Application of the unity rockfall model to variable

surface material conditions. EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017. Poster presentation.

  • View abstract

    ​Rockfall is a geological process that poses risks to the safe operation of transportation infrastructure in mountainous environments worldwide. The work presented here builds on work by Ondercin et al. (2016) demonstrating the applicability of 3D video game engines for the development of realistic rockfall simulations. Further development of the model is being completed with an emphasis on calibration using data from sites in British Columbia, Colorado and New Zealand. Each dataset provides information collected using a variety of remote sensing techniques, including terrestrial and aerial LiDAR as well as oblique aerial photogrammetry. The research reported here explores the ability of the game engine based modelling technique to simulate rockfall under the variable surface conditions present at each of the sites. This includes steep natural rock slopes, with debris-talus cover, as well shallower slopes with soil cover and vegetation. A comparison of the setup, model inputs and methods implemented in the model for each case study is presented.

  • View abstract

    Debris flows that are confined by canyons generally exhibit distributary behavior once they exit the canyons, usually creating some sort of debris fan. This distributary nature is commonly observed in fluvial processes, as avulsion out of established flow paths allows the system to methodically fill topographic lows and develop regular, fan-shaped deposits. For debris flows, avulsion represents a serious hazard, because future debris flows may occur in areas that have not experienced events in the recent past, and flows may occur at significant distances across the fan away from currently active channels. It is important to be able to identify avulsion-susceptible areas, to quantify the likelihood of avulsion, and to model and mitigate the possibility of avulsion. Map views of several debris fans showing locations of successive events were analyzed to evaluate the degree of avulsion. In addition, cross-fan sections at three locations in Colorado were interpreted stratigraphically and analyzed to calculate a modified compensation index, Kcv, a single number that indicates significant avulsion activity (Kcv near one), or low avulsion activity (Kcv near 0.5). Areas with typical debris-flow characteristics (abundant coarse clasts, thick units, large lobes, high clay content) tended to have higher compensation indices than areas with typical stream-flow characteristics (thinner, with less clay and coarse clasts). Finally, several sites are reviewed where an understanding of avulsion could help anticipate flow behavior and direct mitigation efforts.

     

  • View abstract

    Gas hydrates form within deep-water marine sediments, and may pose an offshore geohazard when changes in temperature or pressure lead to hydrate dissociation. Recent drilling expeditions show that stiff, ice-like hydrate readily forms within fine-grained marine soils as complex, near vertical vein structures. Testing of intact fine-grained hydrate bearing sediments has suggested that the host soil matrix may be underconsolidated given the depth from which they were recovered. This paper presents the results from a series of unconsolidated undrained triaxial shear tests carried out on laboratory prepared fine-grained soil specimens containing vertical, cylindrical, synthetic hydrate veins of different diameters. The test results are used to discuss how hydrate vein formation may lead to the apparent underconsolidation of marine sediments, and the potential impact of this underconsolidation on the dissociation behaviour of the sediment.

  • View abstract

    Embankments in the Arctic are usually constructed during winter conditions to preserve the underlying permafrost and minimize environmental impacts. However, there is limited understanding as to how frozen soils compacted during winter conditions behave and how it impacts the overall performance of the embankment, especially during the first thawing season following winter construction. A series of direct shear tests were conducted on laboratory-prepared frozen soil to determine its shear strength properties using a large-scale direct shear equipment. Normal stresses of 25, 50, and 100 kPa were selected corresponding to the range of stresses expected in the field. Tests were conducted in an environmental chamber under frozen and thawed conditions. This paper presents the preliminary results of a testing program to understand the behaviour of high embankments with fill materials compacted frozen and experienced thawing.

Strouth, A. 2017. Toolbox for decision making. 96th Annual Meeting of the Transportation Research Board, Engineering Geology Committee Meeting (AFP10), Washington, DC, 8-12 January 2017. Invited presentation.

  • View abstract

    Guatemala City is now the most populous city in Central America, in part due to rapid migration of people from rural areas. Resulting population pressure on the limited geographic area of the city has led to many settlements in steep ravines. The ravines are prone to landslide activity and the inhabitants are at risk. Mitigation of the landslide risk to acceptable levels is typically cost-prohibitive. Permanent relocation is the only option to eliminate the risk. However, there are several economic and social obstacles impeding successful implementation of a relocation program. In response, landslide risk reduction projects focusing on education of community members have been developed. In the present project (CERRPED), a training course has been developed to teach community leaders how to use landslide risk evaluation and mitigation tools to assess their risk to small landslides (typically the size of a house or less). Affordable mitigation options are also introduced. To date, pilot training sessions have been well-received by community members, and a plan for widespread implementation is beginning with input from Guatemala’s federal agency for disaster reduction (CONRED). Use of CERRPED by the communities will be evaluated in the future to determine if it is having a positive effect on landslide risk reduction.

  • View abstract

    ​Ecosystems within the subhumid Boreal Plains of Northern Alberta host ecologically and commercially significant habitat and natural resources. However, these ecosystems exist under a delicate hydrologic balance that may be upset as the climate warms by 2 to 5 °C over the next century. In this study, numerical simulations were used to predict climate change impacts at a catchment composed of a mosaic of Boreal Plains ecosystems including a small pond, peatlands with sparse black spruce, and hillslopes with predominantly aspen forests. Simulations were conducted with a fully integrated groundwater–surface water code using a 2-D model previously calibrated to a decade of hydrologic data that included a range in climatic conditions. Projections from 13 climate change scenarios were simulated from 2011 to 2090 and compared to a base case scenario that assumed no climate change. Results indicate peatland water levels may decline by up to 1 m; however, sensitivity simulations indicate that the decline in water levels may be moderated by several feedback mechanisms that restrict evaporative losses and moderate water level changes. In contrast, higher evapotranspiration losses from the aspen hillslopes are predicted to result in near-surface soils becoming increasingly drier. Thus, the aspen may frequently be water stressed and increasingly susceptible to secondary maladies such as pests and disease. Reduced pond water levels are also predicted with the development of frequent ephemeral conditions in warmer and drier scenarios. Concurrent decreases in stream flow may further impact downstream ecosystems. Further research into the regional health and sustainability of Boreal Plains ecosystems is warranted and could benefit from the development of improved numerical tools capable of extending the processes considered.

     

  • View abstract

    BGC Engineering Inc. (BGC) is an applied earth sciences consulting firm with offices across Canada as well as in the United States and Chile. BGC works to aid our pipeline clients in managing a variety of geotechnical and hydrotechnical hazards, employing a systematic approach to prioritize sites for inspection, monitoring, and mitigation. Pembina Pipeline Corporation (Pembina) owns and operates over 500 km of oil pipelines in the Swan Hills region of Alberta (Figure 1). BGC has been working with Pembina since 2007 to manage risks posed by geohazards to the safe operation of their pipeline network. The geotechnically challenging terrain in this area presents a significant inventory of geohazards including deep-seated landslides in bedrock, shallow to moderate depth slides and slumps within surficial soils, and stream bank erosion. Working with Pembina, BGC utilized multi-temporal Airborne Laser Scanning (ALS) data to perform topographical change detection analyses, to assist in identifying and characterizing geohazards and recognizing anthropogenic changes within, or in proximity to, the pipeline rights-of-way. BGC has used this tool as input to a screening process to prioritize sites for detailed field inspection. We also present a case in which ALS change detection was used as an immediate response to develop mitigation strategies for a pipe that had become exposed to an active landslide.

  • View abstract

    Using change detection and semi-automated identification methods, it is possible to extract detailed rockfall information from terrestrial laser scanning data to build a database of events, which can be used in the development of the frequency-magnitude relationship for a slope. In this study, we have applied these methods to the White Canyon, a hazardous slope that presents rockfall hazards to the CN Rail line in British Columbia, to build a database of rockfalls including their locations, volumes, and block shapes. We identified over 1900 rockfall events during a 15-month period, ranging in volume from 0.01 to 45 m3. The frequency of these events changed throughout the year, with the highest periods of activity occurring over the winter months. We investigated how the sampling interval, or duration between scans, can affect how the rockfalls are identified, and therefore the frequency-magnitude relationship for the slope using datasets with fewer scans. We show that as the duration between scans becomes larger, fewer rockfalls are detected, as multiple events that have occurre​d in the same location cluster together into a single event. The results of this study can be used to assist the railways in planning the appropriate number and duration between future scans, in order to capture frequency-magnitude data for the slope with a desired level of detail.

  • View abstract

    Railways in Western Canada traverse many hazardous slopes, which are the source of frequent rock fall events. An understanding of the rock fall frequency-magnitude relationship can be used in hazard analysis for these railway lines. The White Canyon is an active slope along a 2.2 km section of CN Rail track in British Columbia which is managed by rock protection sheds, ditches and warning fences. Due to the high frequency of activity throughout the slope, maintaining rock fall records with details on locations and volumes can be difficult using methods of track-level inspection or monitoring systems. Over the past five years we have collected Terrestrial Laser Scanning (TLS) data at the White Canyon as a part of the Canadian Railway Ground Hazard Research Program and recently have refined data collection and processing methods such that we have been able to identify thousands of rock falls on the slope in a two-year period, and calculate their volumes, using 3-dimensional change detection and an automated rock fall detection process. These refined methods have allowed us to develop a database containing a high level of detail, especially in the upper slopes. We have used these data to build an understanding of how the time elapsed between site visits for data collection can affect our ability to identify rock falls on the slope. The lessons learned through this process provide insight into the design of future terrestrial monitoring campaigns for this and other slopes.

  • View abstract

    Pembina Pipeline Corporation manages 700 km of oil pipelines in the Swan Hills region of Alberta, approximately 500 km of which are currently in operation. The challenging terrain in this area presents a significant inventory of geohazards to the safe operation of the pipelines including deep-seated landslides in bedrock, shallow to moderate depth slides and slumps within surficial soils, and stream bank erosion. In this paper we explore the use of Airborne Laser Scanning (ALS) change detection to assist in identifying and characterizing geohazards and recognizing anthropogenic changes within, or in proximity to, the pipeline right-of-ways. Sixty areas within a 4,800 square kilometre study area were evaluated using ALS data spanning eight years. This process was used as part of a screening process to prioritize sites for field inspection and detailed assessment based on the observed activity and the pipeline’s vulnerability to the hazard. We also explore the limitations of this analysis in identifying ground changes based on the geometry and type and direction of the movement, as well as the limitations and errors that are introduced when comparing data of varying quality, as the capabilities of ALS are continually improving.

  • View abstract

    Railway tracks over peat subgrades can experience large ground deformations, increased pore-water pressures, formation of pumping holes, and pumping of fines during the passage of trains, which can lead to accelerated track deterioration and risk of derailment. One approach to mitigate these issues is to improve the subgrade stiffness using mass stabilization, which involves mixing a binding agent, such as cement, into a soil to improve its physical properties. This paper describes the development and use of a method to calculate trackbed modulus to quantify the improvement due to mass stabilization at a site with peat subgrade. Track modulus was calculated using in-service freight trains by measuring track displacements using digital image correlation and wheel loads from a nearby wheel impact load detector. Because of the voids that existed between the rail, sleepers, and ballast it was found that using displacements of the ballast crib to calculate the trackbed modulus, instead of the overall track modulus using rail or sleeper displacements, provided a way to quantify the improvement of the subgrade that was not affected by the presence of voids. The results indicate the post-rehabilitation trackbed modulus was double the original baseline value for the track section, indicating that mass stabilization can be an effective rehabilitation strategy to improve the stiffness of problematic peat subgrades

  • View abstract

    Objectively forecasting the runout of a potential open pit slope failure, in addition to identifying the failure itself, is a critical component of a mine’s risk management plan. Recent losses arising from large open pit slope failures demonstrate shortcomings in current practice. A dataset of 105 pit slope failures was compiled to compare open pit runout trends against established empirical runout relationships for natural landslides. Fahrböschung angle versus volume and Fahrböschung angle versus slope angle relationships provide reasonable runout estimates. Open pit slopes have the advantage of removing the influence of morphological features, vegetation, and liquefiable substrates while controlling the travel path angle and roughness. In such a controlled environment, landslide mobility has a strong sensitivity to slope angle, material properties, and fall height, and is only modestly sensitive to volume. A grouping of highly mobile open pit slope cases involving weathered, saturated, collapsible rock mass materials exceed expected runout distances when compared with established runout trends. This suggests mobility for these weaker rock masses is controlled by pore pressures mediating basal friction. The result is that two different runout exceedance trends are observed based on whether the unstable rock mass involves fresh, strong rocks or weathered weak rocks.

     

  • View abstract

    The high consequences of recent large open pit slope failures have increased industry and regulatory interest in establishing exclusion zones beneath an impending pit wall failure. This paper proposes a methodology to delineate an exclusion zone for an impending pit slope failure. The focus of this paper is a framework for the management of life loss risk to the most exposed individual. The probability of the landslide occurring and the probability of the resulting landslide being very or extremely rapid are described in this paper. Set in a probabilistic framework, empirical runout analysis tools are useful for estimating the spatial probability of impact throughout the open pit and establishing exclusion zones. Runout exceedance probability charts calibrated to a large dataset of pit slope failures are provided. The temporal probability that the most exposed individual is present and cannot be evacuated is also described. The resulting risk is mapped across the pit floor by dividing it into square grid cells and calculating the probability of death to the most exposed individual for each cell. The cells can be colour coded to indicate specific risk exposure ranges relative to the exclusion zone set. A conceptual case study is used to illustrate the proposed methods.

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