Passive Groundwater Depressurization System for Improving Road Embankment Stability, Case Study: Powerview Creek, Manitoba

R.M. Kenyon

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: CASE HISTORIES - IV Miscellaneous

ABSTRACT: A passive groundwater depressurization system was implemented as an initial element of slope stabilization works along a highway embankment near Powerview/Pine Falls, Manitoba. The embankment and concrete box culvert at the Powerview Creek crossing had been actively moving for several years, resulting in a separation of the culvert, and a protracted maintenance schedule for this section of highway. A passive depressurization system consisting of a series of drilled wells, discharging by gravity, was installed to reduce the artesian piezometric pressures acting on the lacustrine clay foundations. Monitoring data indicated a reduction of up to 6.5 m in the driving piezometric pressures within the bedrock and till. Overlying clays responded incrementally, with pressure declines of between 3.0 m and 6.0 m within deep silts and clays immediately overlying the tills, and in the order of 1.0 m within the shallow clays. Back analysis of the slope stability condition, coupled with seepage analysis, indicated an improvement of approximately 10% to the overall stability of the embankment by groundwater depressurization alone. Passive groundwater depressurization was executed at relatively low cost in comparison to more traditional stability improvement measures and allowed the Owner additional time to explore several options such as rockfill shear columns and light weight embankment fill for replacement of the failed box culvert.

RÉSUMÉ: de stabilisation des pentes le long d'un remblai d'autoroute près de Powerview / Pine Falls, au Manitoba. Le remblai et le ponceau en béton au croisement de Powerview Creek se déplaçaient depuis plusieurs années entraînant une séparation du ponceau et le prolongement du programme d'entretien pour ce tronçon de route. Un système de dépressurisation rgeant par gravité, a été installé afin de réduire les pressions réduction allant jusqu'à 6,50 mètres dans les pressions piézométriques de conduite dans le substratum rocheux et de till. Les argiles sus-argiles et des limons profonds recouvrant les tills, et de l'ordre de 1 mètre dans les ad'environ 10% de la stabilité globale du remblai uniquement par la dépressurisation des eaux souterraines. La dépressurisation passive des eaux souterraines a été réalisée à un moindre coût comparé à d'autres mesures matériaux existants dans les remblais par de matériaux plus légers en place de la boîte ponceau à remplacer.

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