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The effect of vibro-replacement ground improvement on the mechanical response of a low-plastic silt was examined using constant-volume monotonic and cyclic direct simple shear (DSS) testing. The silt samples representing "pre-improvement", "post-improvement", "post-improvement-aged" phases were retrieved from the field for testing. The pre- and post-improvement silt specimens consolidated to in-situ stress state, under constant-volume monotonic DSS shearing, displayed no strain-softening. Cyclic-mobility type strain accumulation with a stress-history-normalizable response was noted when pre- and post-improvement silt specimens were tested under constant-volume cyclic DSS loading, in spite of the ground improvement imparted in the latter case. In contrast, the post-improvement-aged silt specimens at in-situ stress state displayed a dilative strain hardening response. Under similar cyclic stress ratios, the rate of build-up of excess pore water pressure with increasing number of loading cycles was found to be least for the post-improvement-aged silt specimens when compared with pre- and post-improvement cases. As such, the cyclic resistance ratio of the post-improvement-aged silt specimens were significantly higher when compared with those from pre- and post-improvement silt specimens. These findings also highlight the importance of understanding the effects of vibro-replacement on the soil fabric/microstructure especially considering the time elapsed since the application of ground improvement. • No systematic laboratory studies to understand the effect of ground improvement on the mechanical response of silt. • Laboratory study was undertaken to assess liquefaction resistance of silt due to ground improvement using vibro-replacement. • The study findings show the importance of elapsed time after treatment in improving the silts subjected to vibro-replacement. [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 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]

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.)