Crack repair in a pedestrian underpass tunnel

Client: CPB
Location: Leongatha, Victoria
Sector: Road Infrastructure

The 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.

Crack Repair

Ironstone Civil was engaged to develop, in conjunction with our client and the asset owner’s engineers, a solution to stabilise the base of the tunnel and repair the extensive cracks.

This defect had developed a high profile amongst the various stakeholders, and it was preventing practical completion of the Head Contract.

The tunnel needed to be closed during repairs requiring pedestrian traffic to take a long detour, so keeping the closure to a minimum during repairs was important.

We fully detailed the methodology, ITPs,  and QA so that all stakeholders could track our progress and the quality of the work.

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.