Hwy 7-8 Pedestrian Bridge

Scope: Caissons

The Project

The Region of Waterloo conducted a feasibility study for a new Highway 7/8 Cycling and Pedestrian Bridge between Chandler Dr. and Avalon Place. It was determined that the proposed bridge would provide easier access for pedestrians and residences on both sides of Hwy 7/8.

The Challenge

Due to the large free span bridges, oversized foundations are required to support the excess loads imposed by the structure. The foundation locations were specific and predetermined and could not be changed. As a result, a foundation solution was required to be installed in a location where poor soils were present and within proximity of existing and sensitive services. Based on the soils investigation, it was also determined that the soil was conducive to basal heave in the saturated silts and sands.

The Solution

Maple Site Solutions Inc. was contracted to provide a deep foundation solution keeping the challenges in mind. Maple Site Solutions Inc. used an 1800 mm diameter segmental casing system while utilizing a polymer slurry procedure to eliminate the potential for any basal heave while drilling holes to depth. Polymer slurry was added to the hole to maintain a constant head pressure and counteract the basal heave conditions. Once the hole was complete, the consultant implemented a squid test. This test was conducted under the slurry in order to determine the cleanliness of the hole and to measure the silt fines present at the base of the hole.