Queensland Bridge Re-levelled with Teretek®

A two-lane concrete bridge that crosses a creek in the Sarina Range, located in the Mackay-Whitsunday region of Queensland, had become un-level due to a pier subsiding on one side of the bridge deck. The bridge provided the only road access to several nearby properties, with no alternative route available.

The foundation ground beneath the concrete bridge piers and footings was gravel sand and relatively shallow, with a depth of approximately 400mm between the footing pad and bedrock beneath. The piers were also permanently exposed to water from the creek.

The north side pier of the bridge had settled into the ground along a distance of 1800 lineal metres, causing the bridge deck to sink by 130mm on one side. A solution was sought to re-level the bridge to help ensure it remained in good working condition and was able to safely service the community into the future.

One option was to dismantle, repair and then rebuild the bridge deck, however this was not possible without significant expense and disruption to local residents.

After considering various options to re-level the bridge, Mainmark was consulted to help address the issue using Teretek® resin injection solution.

Mainmark was required to re-support and re-level the bridge pier and rectify the ground settlement to help ensure it could continue to safely bear the weight of constant traffic, including heavy vehicles.

It was also important for Mainmark to deliver the solution quickly, efficiently and cost-effectively, with minimal disruption to local traffic.

Mainmark addressed the ground settlement that had caused the bridge pier to subside using its proprietary engineered resin injection solution, Teretek®; a unique two-in-one solution that delivers both ground improvement and re-levelling capability, which was ideal for the project conditions. The structural resin is environmentally inert and completely impervious to water.

Using a process that is likened to keyhole surgery, the engineered resin solution is applied quickly and unobtrusively via small, precise injection points.

As the pad footings were small, measuring 1200x1800mm, Mainmark recommended the use of hydraulic jacks to lift and support the bridge, ensuring the stability and safety of the structure as the resin was being applied to the foundation ground.

A total of 870kg of Teretek® solution was injected, using a bespoke injection application process designed to achieve maximum lift and ground strengthening. The bridge was able to remain open with traffic control in place throughout the remediation process.

Although two days had been allocated for the project, Mainmark was able to successfully complete works and return the bridge to within 13mm of its original level within just 8 hours, allowing the bridge to resume full operation earlier than planned.