Flow of combined particulate media and fluids is relevant to many industrial applications and natural phenomena, yet, not fully understood due to its complex physics. Over the past five decades, significant achievements were accomplished in particulate flow modeling aided by the rapid advances in computer hardware. It is notable that most of the major developments in particulate flow modeling were presented in the context of chemical engineering (e.g., fluidized beds and pneumatic conveying), while contributions to civil and geotechnical engineering are still relatively limited. One of the main reasons for this relatively small contribution is the inherent large-scale nature of many geotechnical applications such as earth dams and natural slopes, which are computationally expensive to model. Although different up-scaling techniques were presented to overcome the obstacle of high computational cost, the accuracy of up-scaled simulations is still questionable. Therefore, it is important for geotechnical engineers and researchers to have a good understanding of particulate flow methodologies and its corresponding accuracy and computational cost. This study aims to present a critical summary of the existing approaches for particulate flow modeling and their direct application to geotechnical problems. The majority of existing models can be classified into three main categories from the perspective of the numerical solution: Eulerian–Eulerian, Eulerian–Lagrangian, and Lagrangian–Lagrangian models. Under this classification, we discuss the different models presented to date and the advantages and disadvantages of each model. Our evaluating criteria depends on the accuracy of results, computational expense, and availability of modeling tools (e.g., commercial or open source codes). We also include a brief review of published work in the geotechnical field, in which, these different models were used. We believe that this study would help geotechnical engineering practitioners to identify the available methods, modeling tools, and challenges associated with particulate flow modeling.

This paper presents the summary of a seepage remediation strategy put in place to mitigate the supernatant water seepage observed underneath a tailings retention dike at a mine site located in a permafrost environment in Northern Canada. Effective seepage mitigation was achieved through adaptive tailings deposition sequencing. Following the first observations of a seepage, field investigations and extensive numerical modelling were performed to understand the seepage mechanism, establish appropriate mitigation options and quantify the efficiency of the mitigation strategy over time as the tailings storage facility was operated and sequentially raised. In addition, the seepage mechanism understanding gained was incorporated into a detailed Trigger Action Response Plan for the dike. This paper provides an overview of the evolution of the situation over the operational life of the structure, which is now nearing closure stage, and provides insights about the use of tailings deposition as a seepage mitigation tool.

A 36 m section of railway embankment was remediated on Canadian Pacific Railway’s (CP) Scotford subdivision to address issues of ongoing settlement and mud pumping. The track panel and embankment materials were replaced with new materials inclusive of a geotextile between the ballast and subballast layers, and a wicking geotextile between the subgrade and subballast. The wicking geotextile is designed to draw the moisture from the base of embankment and surface of subgrade towards the shoulders. This site provided the opportunity to monitor the seasonal changes of moisture content within the clayey subgrade and to evaluate the effectiveness of the chosen remediation method. 5TE moisture sensors are installed at both the remediated section and an adjacent control section, along with access tubes for the use of a “Diviner 2000” probe to measure profiles of moisture with depth. This allows for a direct comparison of the performance of the two sections under the same meteorological conditions. Currently the change of volumetric water content (VWC) within fill and subgrade is being measured by 5TE moisture sensors twice daily and profiles of VWC are obtained every two weeks. This paper will present a comparison of the trends of the VWC with time between the two adjacent sites along with the impacts of precipitation events and a spring thaw; and, an interpretation of the impact of these changes in VWC on the unsaturated strength of the soil based on laboratory testing results.

Roadway embankments approaching a culvert or bridge are often constrained by retaining walls due to limited space. Flexible retaining walls such as reinforced earth wall and reinforced soil slope (RSS) are generally used as they are tolerant of the ground settlement under the weight of embankment fill. However, if the face units of the reinforced earth wall and RSS are not properly designed and constructed, the serviceability of the roadway could be significantly affected.
This paper presents a case study of RSSs along Bathurst Street in the Region of York, Ontario. Six RSSs were designed to be up to 10.4m in height reinforced with geogrids at vertical spacings of 0.6m for the roadway embankment over three culverts. The slope angle was 70o and slope face units consisted of vegetated geocells. Two years after the RSS construction, the face units of one RSS collapsed after a significant rain event. Field investigation and global stability analysis were carried out. It was found that the possible failure mechanisms of the RSS were the infiltration rate of surface water exceeded the drainage capacity of the RSS and the built-up hydrostatic pressure exceeded the sliding resistance between the geocells. The failed face units were then reinstalled using the same geocells with the installation of a vertical drainage layer behind the geocells. Following the reinstallation of the face units of the RSS, ground movement monitoring was conducted for all RSSs over the culverts. Field inspection was carried out one year after the reinstallation of the face units. It was found that all RSSs were globally stable. The reinstalled face units were stable. However, localized soil erosions and geocell displacement were observed at the face units of remained five RSSs. Improvements for the design and construction of the RSS are recommended.

Advisian was retained to undertake a dam safety review (DSR) for a client. The facility was constructed in the 1970’s and very limited technical and background information was available for the facility. Further, no previous DSR was completed for the facility since it was constructed in the early 1970’s and no geotechnical data required to complete the DSR were available. Consequently, Advisian recommended geotechnical and geophysical investigations to capture the necessary data to complete the DSR for the dam.

The geotechnical investigation included advancement of seven (7) boreholes through the dam fill into the foundation material, the depths of the boreholes ranging for 11 to 20 meters (m) below ground surface. The geotechnical field program also included the installation of 10 vibrating wire piezometers in six (6) boreholes and one slope inclinometer casing in the seventh borehole. To provide complementary information on the internal dam structure and the underlying native material, a geophysical investigation was completed using electrical resistivity tomography (ERT), multichannel analysis of surface waves (MASW) and seismic refraction methods, along 4 lines spanning 120 m to 240 m long. Data interpreted from the two investigations were utilized to complete the dam modelling and assessment.

The DSR activities followed the 2013 CDA Guidelines. Two separate DSR reports we submitted to the client, namely a report related to the liquefaction and risk analyses and a report for other activities.

Geotechnical recommendations for the new smelter building included, among other, shallow foundations and a cast-in-situ piling (were subsequently substituted by micro piles).

This paper discusses the geotechnical and geophysical investigations findings and sheds light on the lessons learnt from the investigations and the finding of the DSR.

Generation and redistribution of excess interstitial pore water pressures generated during a seismic event can lead to the instability of tailings impoundments after the earthquake. In such cases, the driving forces induced by the event tend to exceed the available shear strength of the retaining dike materials. Examples of such ruptures include the Mochikoshi tailings impoundment (1978) and the Lower San Fernando Dam (1971), which occurred one day and thirty seconds, respectively, after the events.

This paper will present numerical analyses to evaluate the post seismic stability of a tailings impoundment with upstream dikes constructed with a downstream slope of 1V:8H, with and without waste rock inclusions. The tailings are modelled in the shaking phase using FLAC and the PM4SAND constitutive model, with parameters calibrated based on an extensive laboratory and field-testing program. The post-seismic stability of the tailings impoundment is assessed by performing a static analysis based on the final shaking conditions with a shear strength reduced by the excess pore water pressures.

The results show that even if the impoundment without inclusion shows limited displacements at the end of shaking, an unstable zone surface may develop due to excessive shear strains during the post-seismic phase. Such large displacements can lead to failure of the supporting dikes. Conversely, an impoundment with waste rock inclusions tend to show much smaller displacements under post-seismic conditions, even when excess high pore water pressures are generated during shaking.