Vertical stress distribution in soil - bentonite slurry walls

Rahul V. Mukherjee, Moir D. Haug

In the proceedings of: GeoManitoba 2012: 65th Canadian Geotechnical Conference

Session: T3A - Soil Mechanics III

ABSTRACT: -slurry wall trenches has the potential to significantly reduce the effectiveness of these walls. Soil-bentonite (SB) slurry walls are one of the most popular techniques to minimize the horizontal migration of contaminants. This technique involves the excavation of a narrow trench in the presence of bentonitic slurry down through permeable strata and backfilling with a low permeability material. This paper presents the results of a laboratory testing program and modelling study to investigate the vertical stress distribution in slurry walls. The program was conducted to supplement the design and installation of an 11,000 m long slurry wall. This slurry wall is being installed through low hydraulic conductivity glacial till containing intermediate permeable zones. The depth of this 1 m wide slurry wall is approximately 50 m. Backfill hang-up in these deep walls is a particular concern. In order to -ry to determine friction along the wall of the trench. The testing program involved large strain consolidation testing of selected field backfill samples. A Marriott bottle system was also employed to continuously measure hydraulic conductivity and lateral stress during testing. Additional backfill samples were tested to provide data on sensitivity of horizontal and vertical stress to variations in backfill fines content. An analytical model and a coupled seepage stress-strain finite element model (FEM) were used to predict vertical stress changes with time and depth for the different backfill materials. The results of the research study found that trench width was the most important variable in determining wall hang-up. It also showed that the upper portions of the backfilled trench may take years to consolidate and thus provide the desired level of impermeability.

RÉSUMÉ: La voûte ou la paroi moulée -populaires pour limiter la migration horizontale modélisation de la distribution des contraintes verticales dans les parois moulées. Le programme a été réalisé dans le 000 m de long. Cette paroi est en cours de cette paroi moulée de 1 e long de ces parois , il est nécessaire de déterminer le niveau de dmesurer en continu la conductivité hydraulique et la contrainte latérale durant les essais. Des échantillons de remblai supplémentaires ont été testés afin de fournir des données sur la sensibilité des contraintes horizontales et verticales en fonction de la fraction de particules fines contenues dans le matériel de remblai. Un modèle analytique et un modèle par éléments finis (FEM) ont été utilisés pour prédire les changements de contraintes verticales en en fonction du temps et de la profondeur de chacun des différents matériaux de remblai. ur déterminer 1. INTRODUCTION The potential for slurry wall backfill arching and hang-up was examined in a laboratory testing program. The permeability of clay till slurry backfill is highly dependent on the load placed on the backfill. As a result permeability usually decreases with depth as the backfill consolidates slowly under increasingly high loads. If the width of the backfill trench is narrow and the depth great, there is a potential for arching and backfill hang-up. Laboratory testing was carried out to characterize changes in hydraulic conductivity and the coefficient of lateral earth pressure with increase in effective stress. Soil-bentonite (SB) slurry walls are one of the most popular techniques to minimize the

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Rahul V. Mukherjee; Moir D. Haug (2012) Vertical stress distribution in soil - bentonite slurry walls in GEO2012. Ottawa, Ontario: Canadian Geotechnical Society.

@article{Paper373,author = Rahul V. Mukherjee; Moir D. Haug,title = Vertical stress distribution in soil - bentonite slurry walls,year = 2012}