Crack repair in a pedestrian underpass tunnel

Problem:

Extensive cracking developed in this new pedestrian underpass tunnel due to stresses caused by the subsidence and twisting of the tunnel. Poorly compacted foundation soils were the likely root cause.

Solution:

Ironstone Civil understood several stakeholders had a keen interest in the solution and execution of the works and that we would be under heavy scrutiny.

The tunnel had been constructed with precast sections and the floor was cast in situ concrete.

Contact grout and then a multi-component acrylate gel was injected below the ground slab to re-establish uniform foundation support for the slab. Special care was taken to avoid blocking sub slab drains.

Once the slab had been stabilised concrete crack repairs were carried out on the floor, walls and sofit of the tunnel. As a precaution water stop materials were on hand to stop any water leaks if they arose.

The project was completed safely, on time and on-budget and to a very high-quality standard.