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A series of full-scale experiments was conducted to estimate lateral soil constraints on pipes buried in dense sandy slopes at different burial depths. The experimental data indicated that the soil force on the pipe increases with increase in the slope grade and burial depth ratio. The lateral soil force against relative pipe displacement response observed from the experiments is presented and compared to those arising from level ground conditions. The study was extended to larger burial depth ratios by simulating pipes under sloping ground conditions using a numerical (finite-element) model that was initially calibrated using the results from physical modelling. The findings from the study in terms of the variation of peak lateral soil restraint as a function of the slope grade and burial depth ratio are presented for consideration in pipeline design. [ABSTRACT FROM AUTHOR]

Muskeg soil is widespread in Canada. It covers around 15% of the Canadian landscape. Its problematic nature is attributed to its high compressibility and low shear strength when subjected to loads because of its high initial void ratio and water content. Therefore, in this study, microbially induced calcite precipitation (MICP), an emerging and potentially environmentally friendly technique for soil stabilization, is used for enhancing the compressibility and shear strength properties of muskeg soil. The urease active bioslurry approach is adopted in this study, which comprises the mechanical mixing of bioslurry with soil and the injection of cementation solutions in subsequent phases. Muskeg soil was collected from Bolivar Park, Surrey, British Columbia, Canada. Different bioslurry concentrations were tested for the compressibility properties to determine the optimum concentration. Afterward, the optimum concentration was used to check the effect of the bioslurry percentage by weight and the number of cementation solutions injected on the soil stiffness and strength. Microstructure analysis by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were conducted for untreated and treated samples to check the change in the soil microstructure due to stabilization. The results showed that the 0.4 mol/L bioslurry concentration demonstrated the best compressibility properties. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Organic soils are considered one of the most problematic soils due to their high compressibility and low shear strength at small strains. Characterizing organic soils based on their simple index properties is useful for the preliminary design stages of construction projects. There are three main index properties used for assessing organic soils properties, namely: the water content, the organic content, and the fiber content. Organic soils are distinguished by their relatively high water content. The organic content includes the carbonaceous and combustible components. Whereas the fiber content accounts for the presence of fibers in organic soils based on their botanical composition and the degree of decomposition. The data available in literature regarding organic soils parameters (index, compressibility and shear strength) were collected and analyzed in this study to obtain new correlations between the different organic soil parameters, and the simple index parameters (water content and organic content). The available correlations found in the literature depend on relating a certain parameter with either the organic content or water content. However, the organic content and the water content are related. Hence, the proposed correlations presented in this study aim to connect the particular soil parameter with both the water content and the organic content, using the same equation. Unfortunately, there is not much data in the literature about the soil texture or fiber content, and their relation with other parameters. Hence, all the proposed correlations in this study are not considering the fibre content or the soil fabric. [ABSTRACT FROM AUTHOR]

Experiments were carried out to characterise the influence of soil water retention properties on the corrosion of a cast iron specimen buried in Fraser River silt. The corrosion rates were measured at different degrees of saturation using standard corrosion tests, along with separate water retention tests for the Fraser River silt. Building on previous work on this topic, a numerical model solving moisture flow, oxygen diffusion, electrical conductivity and their coupled influence on metallic corrosion in unsaturated soil was developed. The experimental data and preliminary numerical modelling results were then used as inputs to a field-scale numerical model to examine climate-induced moisture migration around a pipeline and the resulting levels of corrosion. The time-dependent corrosion mass loss and the resulting loss in pipe wall thickness of a buried pipeline were modelled, and it was demonstrated that the cyclic climatic variations predominantly perturb the corrosion rates during the initial cycles, and subsequently a gradual corrosion rate arises depending on general climatic conditions. Further analysis of the influence of electrical resistivity on the levels of corrosion revealed that a decrease in resistivity due to effects such as seawater intrusion or naturally saline soils may result in a significant increase in the levels of localised corrosion. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The direct simple shear (DSS) device is one of the commonly used laboratory element testing tools to characterize the shear behaviour of soil. The interpretation of results from an element test requires understanding of the degree of stress and strain non-uniformities in a given test specimen. So far, studies on stress and strain non-uniformities in the DSS test have been conducted using direct boundary measurements of stresses in laboratory specimens supported by a continuum based analytical approach. Discrete element modelling now provides a means of modelling the soil behaviour in a realistic manner using a particulate approach. Accordingly, the performance of a DSS specimen was modelled using discrete element modelling with emphasis on assessing stress and strain non-uniformities in the specimen during shearing. The approach allowed for the numerical determination of stresses not only at the boundaries, but also within the DSS specimen. It was shown that mobilised stress ratio distribution throughout the shearing phase for the majority of specimen volume at locations near the central planes parallel and perpendicular to the direction of shearing is fairly uniform. Finally, it was noted that the potential for particle slippage at locations near the specimen centre can result in non-uniform shear strain distributions. [ABSTRACT FROM AUTHOR]

The performance evaluation of buried extensible plastic pipelines, such as polyethylene pipes in the gas distribution industry, in areas prone to ground movement is a key consideration for many utility owners. Considering the relatively smaller deformation stiffness and nonlinear stress-strain response of these pipes compared with those of steel pipes, a good understanding of the basic soil–pipe interaction mechanisms forms a critical part in these evaluations. The increase in soil normal stress on the pipe attributable to soil dilation and gradual degradation of interface friction with axial pipe displacement was investigated. An analytical method was developed to estimate the pipe response when subject to axial frictional loads arising from soil movements, which accounts for these factors and the nonlinear stress-strain response of the pipe material. For a known relative axial soil displacement, the approach provides a convenient way to determine the axial force, strain, and length along which the friction is mobilized. The proposed analytical solution was used to model the response of five large-scale field pipe pullout tests. It is shown that the analytical solution is capable of effectively forming a framework to relate pipe displacement, pullout resistance, strain, and mobilized length. The findings also highlight the significance and need to account for soil dilation effects in describing the soil–pipe interaction in extensible plastic pipes. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The postcyclic reconsolidation response of low-plastic Fraser River silt was examined using laboratory direct simple shear testing. Specimens of undisturbed and reconstituted natural low-plastic Fraser River silt and reconstituted quartz powder, initially subjected to constant-volume cyclic loading under different cyclic stress ratios (CSRs) and then reconsolidated to their initial effective stresses (σvo′), were specifically investigated. The volumetric strains during postcyclic reconsolidation ([variant_greek_epsilon]v-ps) were noted to generally increase with the maximum cyclic excess pore-water pressure (Δumax) and maximum cyclic shear strain experienced by the specimens during cyclic loading. The values of [variant_greek_epsilon]v-ps and maximum cyclic excess pore-water pressure ratio (ru-max) were observed to form a coherent relationship regardless of overconsolidation effects, particle fabric, and initial (precyclic) void ratio of the soil. The specimens with high ru-max suffered significantly higher postcyclic reconsolidation strains; [variant_greek_epsilon]v-ps ranging between 1.5 and 5% were noted when ru-max>0.8. The observed [variant_greek_epsilon]v-ps versus ru-max relationship, when used in combination with the observed dependence of cyclic excess pore-water pressure on CSR and number of load cycles, seems to provide a reasonable approach to estimate postcyclic reconsolidation strains of low-plastic silt. [ABSTRACT FROM AUTHOR]

Mixing of waste rock and tailings as a homogeneous mixture (referred to as “paste rock”) has been suggested as a favourable approach to overcome deficiencies associated with traditional methods of mine waste disposal. In consideration of the current limited understanding of the fundamental mechanical response of paste rock, a laboratory research program was undertaken to investigate the monotonic and cyclic shear response of paste rock. This paper presents the findings from undrained cyclic triaxial shear testing conducted on saturated paste rock specimens reconstituted such that the tailings would “just fill” the void spaces between the coarse particles of the skeleton. During undrained cyclic loading, paste rock typically exhibited a cumulative decrease in effective stress along with a progressive degradation of shear stiffness. The material generally displayed a higher tendency for strain development under cyclic loading when compared with rock-only and tailings-only specimens subjected to similar consolidation and cyclic loading conditions. However, no strain-softening or loss of shear strength was observed, suggesting that the material is unlikely to experience flow failure under undrained cyclic loading. The cyclic shear resistance was relatively insensitive to the initial effective confining pressure ([IMG]) for the tested stress levels of [IMG] < 400 kPa. Le mélange des roches stériles et des rejets de concentrateur sous forme de pâte homogène (appelée pâte résidus-stérile ou PRS) a récemment été suggéré comme approche de gestion des résidus miniers qui permet de contourner certains problèmes associés aux approches traditionnelles. Puisque les connaissances sont limitées dans le domaine du comportement mécanique fondamental de la PRS, une étude en laboratoire a été initiée dans le but d’évaluer le comportement en cisaillement monotonique et cyclique de la PRS. Cet article présente les résultats obtenus lors des essais triaxiaux en cisaillement cyclique non drainés effectués sur des échantillons de PRS saturés reconstitués de telle façon à ce que les rejets remplissent tout juste les vides entre les particules de roches stériles. Pendant le chargement cyclique non drainé, la PRS présente typiquement une diminution cumulative de la contrainte effective ainsi qu’une dégradation progressive de la rigidité en cisaillement. Le matériau démontre généralement une plus grande tendance au développement de déformations en conditions de chargement cyclique, comparativement aux échantillons de stérile seul et de résidu seul soumis aux mêmes conditions de consolidation et de chargement cyclique. Cependant, aucun relâchement des déformations ou perte de résistance au cisaillement n’a été observé, ce qui suggère que le matériau n’est pas susceptible de subir une rupture en écoulement lors de chargement cyclique. La résistance au cisaillement cyclique était relativement insensible à la pression initiale de confinement ([IMG]) pour les contraintes testées de [IMG] < 400 kPa. [ABSTRACT FROM AUTHOR]

The idea of mixing mine tailings and waste rock to form “paste rock” prior to disposal is now receiving significant attention from the point of view of sustainable mine waste management practices. This approach has been viewed as a favourable alternative to traditional methods of mine waste disposal because paste rock has the potential to overcome deficiencies (e.g., acid rock drainage and liquefaction-induced failures) associated with traditional methods. To advance the current limited knowledge, a laboratory research program was undertaken to study the mechanical response of paste rock. Testing was undertaken on paste rock specimens prepared so that the tailings would “just fill” the void spaces within the waste rock particle skeleton. The findings suggest that the material is unlikely to experience flow deformation under monotonic shear loading conditions, at least up to the tested initial effective confining stress conditions of 400 kPa. The monotonic shear response of paste rock was found to be similar to that of rock-only material; this finding is in agreement with previous observations from one-dimensional consolidation testing where it had been shown that the rock particle skeleton would carry almost 90% of the externally applied stress on a given paste rock mass. Le concept de « pâte résidus-stériles (PRS), c’est-à-dire le mélange de rejets de concentrateur et de roches stériles avant leur déposition, reçoit maintenant beaucoup d’attention d’un point de vue de gestion durable des résidus miniers. Cette approche est considérée comme une alternative favorable aux méthodes traditionnelles de gestion des résidus miniers puisque la pâte résidus-stériles peut potentiellement pallier à certaines préoccupations (ex. drainage minier acide et ruptures induites par liquéfaction) associées aux méthodes traditionnelles. Afin d’améliorer les connaissances actuelles, un programme de recherche en laboratoire a été élaboré pour étudier le comportement mécanique de la PRS. Les essais ont été effectués sur des échantillons de PRS préparés de façon àce que les rejets remplissent « tout juste les vides entre les particules des roches stériles. Les résultats suggèrent que le matériau a de faibles chances de subir des déformations sous des conditions de chargement en cisaillement monotonique, du moins jusqu’aux conditions testées de contraintes effectives de confinement initiales de 400 kPa. Le comportement en cisaillement monotonique de la PRS est similaire à celui de la roche stérile seule. Ce résultat concorde avec des observations précédentes obtenues lors d’essais en consolidation unidimensionnelle avec lesquels il avait été démontré que le squelette des particules rocheuses pouvait supporter près de 90% des contraintes externes appliquées sur une masse de PRS. [ABSTRACT FROM AUTHOR]

Hydraulic conductivity and consolidation behaviour are examined for an alternative mine waste disposal technique. One type of waste rock, one type of tailings, and mixtures of the same waste rock and tailings were tested in bench-scale and column studies. Specimens 150 mm in diameter were tested for hydraulic conductivity by falling-head method alternated with one-dimensional consolidation, specimens 300 mm in diameter were tested for one-dimensional consolidation response, and specimens 1 m in diameter were tested for self-weight consolidation behaviour in 6 m high columns. Deformation of mixtures under one-dimensional loading was similar to that of waste rock alone and much less than that of tailings alone. Hydraulic conductivity of mixtures was similar to that of tailings alone and independent of specimen diameter. Mixture behaviour was attributed to a homogeneous structure including waste rock in particle-to-particle contact and a continuous, saturated matrix of tailings. The results indicate that mixing waste rock and tailings can produce dense deposits with values of hydraulic conductivity that are orders of magnitude lower than those of waste rock alone, thereby limiting fluxes through the waste and the associated potential for acid rock drainage. Mixture deposits will also have less consolidation-related settlement than tailings, thus improving stability and aiding reclamation. La conductivité hydraulique et le comportement en consolidation sont examinés dans le cadre d’une technique alternative de déposition des résidus miniers. Des essais à petite échelle et en colonnes ont été effectués sur un type de roches stériles, un type de rejets de concentrateur, ainsi qu’un mélange de ces deux matériaux. La conductivité hydraulique a été évaluées pour des échantillons d’un diamètre de 150 mm à l’aide de la méthode à charge variable en alternance avec de la consolidation unidimensionnelle. Des échantillons d’un diamètre de 300 mm ont été testés en consolidation unidimensionnelle. Le comportement en consolidation sous son propre poids d’échantillons de 1 m de diamètre a été évalué dans des colonnes de 6 m de haut. Les déformations des mélanges rejets-stériles en consolidation unidimensionnelle étaient semblables à celles des stériles seuls, et beaucoup plus faibles que pour les rejets seuls. La conductivité hydraulique du mélange était semblable à celle des rejets seuls et était indépendante du diamètre de l’échantillon. Le comportement du mélange est décrit comme une structure homogène qui comprend des roches stériles en contact entre elles ainsi qu’une matrice de rejets de concentrateur continue et saturée. Les résultats indiquent que le fait de mélanger les roches stériles et les rejets de concentrateur peut produire des dépôts denses avec des valeurs de conductivité hydraulique de plusieurs ordres de grandeur sous les valeurs des stériles seuls, ce qui permet de limiter les flux à travers le dépôt et le potentiel de génération de drainage minier acide. Les dépôts mixtes présentent aussi moins de tassements reliés à la consolidation que les rejets de concentrateur, ainsi la stabilité est améliorée et la restauration du site est plus facile. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is commonly assumed that within inundated sand the Skempton B value and P-wave velocity decrease with decrease in saturation. In centrifuge tests a common saturation procedure is to inundate the specimen with carbon dioxide while under a vacuum and then slowly introduce the viscous pore fluid. The B value and related saturation is difficult to measure in centrifuge models and P-wave velocity—saturation correlations have been used for this purpose. A laboratory emulation of centrifuge saturation procedures was made using a triaxial cell with top and bottom bender elements and a viscous methyl cellulose–water pore fluid. Contrary to expectations, the laboratory tests showed high P-wave velocities indicative of full saturation when B values were low. Numerical modeling of the laboratory tests indicated that if air bubbles within the pore fluid are numerous and closely spaced then there is a good correlation between saturation, B value, and P-wave velocity. However if the air bubbles are larger and only present in some of the pores then the P-wave velocity is not a good indicator of B value and average saturation. The laboratory tests also showed that placing the specimen under backpressure for several days increased saturation and related B values. It is suggested that this common laboratory procedure should be considered for saturating centrifuge test specimens. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of pipeline systems during earthquakes is a critical consideration in seismically active areas. Unique approaches to quantitative estimation of regional seismic vulnerability were developed for a seismic vulnerability assessment and upgrading program of a 500-km-long natural gas pipeline system in British Columbia, Canada. Liquefaction-induced lateral spreading was characterized in a probabilistic manner and generic pipeline configurations were modeled using finite elements. These approaches, developed during the early part of this 10-year program, are more robust than typical approaches currently used to assess energy pipeline systems. The methodology deployed within a GIS environment provided rational means of distinguishing between seismically vulnerable sites, and facilitated the prioritization of remedial works. While ground improvement or pipeline retrofit measures were appropriate for upgrading most of the vulnerable sites, replacement of pipeline segments using horizontal directional drilling to avoid liquefiable zones were required for others. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)