Void Filling at Underground Parking Garage in Scarborough

The Challenge

Voids discovered beneath parking garage.

During repair work at the P3 level of an underground parking structure which was 30 feet down, voids were discovered beneath the slab on grade after it was opened up. To fully understand the scope of the issue, the general contractor conducted ground-penetrating radar (GPR) scans and drilled additional boreholes, revealing voids up to 100 mm (4 inches) deep across a 140 m² (1,500 sq. ft.) area. Compounding the challenge was the presence of high groundwater and the inaccessibility of the area to be repaired. Traditional methods of repair would not be able to reach the area in need of repairs.

Key Facts

The Solution

Hydrophobic polyurethane injected in grid pattern.

Groundworks Commercial mobilized quickly, accessing the P3 level via a pedestrian staircase from ground level. With 300 feet of injection hose, the crew was able to efficiently reach the treatment zone without disrupting other areas of the structure.
Injection points were laid out in a 1-meter (4-foot) grid across the affected area. Technicians used a hydrophobic polyurethane to fill the voids and stabilize the slab on grade. The hydrophobic polyurethane was used because it travelled further, pushed away the ground water, and ensured the long-term efficacy of the repair.

The Impact

Voids filled and SOG stabilized.

This solution proved to not only be the best, but really the only practical solution for this parking garage. The inaccessibility of the area needing repairs ruled out any other potential repair options. In spite of this, Groundworks Commercial was able to offer a method of repair that was quick and minimally disruptive, all while still reaching the 30 feet down P3 level of the garage. The work was completed in just two days, with minimal disruption to other ongoing construction activities. Once the injection was finished, the general contractor on site resumed full access and continued their repairs without delay.