Allnorth was commissioned by a St. John’s resident to design and reconstruct a failed concrete block retaining wall. The new wall was construction of concrete blocks from Keystone and measured 2.3m in height and 17m in length. The project consisted of removal of the failed wall, fence, and associated components, and replacing it with the new stone wall using a geogrid system to tie back the face of the structure and create the gravity-based system. a new fence was installed behind the wall using HDPE pipe as the formwork for the new post foundations.
Murray’s Landscape Services Ltd. was the Landscape Architect, and general contractor for the work, Allnorth conducted the structural design for the gravity-based wall.
Challenges faced during the project were as follows:
- A steep embankment on the property to the rear of the subject site. This made construction access difficult and required setting the bottom of the wall somewhat lower than normal into the soil in order to develop the passive resistance at the bottom.
- Various methods were considered for stormwater drainage from behind the wall including possible weeping tile to a rock sump. The final design included clean stone behind the wall with weeping holes to allow the groundwater to trickle from the high side. This alleviated the hydrostatic pressure and prevented erosion of the soil on the adjacent property.
- The geogrid was cut perpendicular to the wall and wrapped around the fence post bases in order to develop the full capacity of the soil.
RESPONSIBILITIES
- Structural design: gravity-based retaining wall
- Construction management
- Site inspection
LOCATION
St. John’s, NL
