Innovation key in Hartmann Bridge restoration
A willingness to look at innovative technology, such as cutting-edge subgrade stabilisation methods used in the recently completed reconstruction of Hartmann Bridge at Toobeah, is helping Goondiwindi Regional Council achieve value-for-money from its reconstruction program, and a better outcome for the local community.
Minnel Road is a north-south through road connecting Toobeah, 40 kilometres west of Goondiwindi, with a large number of agricultural and pastoral properties. While other roads service the area, they are either unsealed or represent a significantly longer route to transport goods to market via the Barwon Highway.
Hartmann Bridge is approximately five kilometres north of the Barwon Highway on Minnel Road and consists of a series of large box culverts and link slabs founded on strip footings over the Weir River.
As a result of flooding in the Weir River in January 2011, the central three box culvert cells sank by up to 175mm. This resulted in sagging of the bridge deck, which made the bridge unsafe for the 70-odd high speed and heavy load vehicles that use Minnel Road each day.
Goondiwindi Regional Council Mayor Graeme Scheu said the actual cost to repair the approved scope of Hartmann Bridge was $327,000, below both Council and the Authority’s original estimates for the project.
“By using the cutting-edge URETEK technology – a pressure-injected expanding resin – Council had achieved both the most durable and best value-for-money restoration outcome,” Mr Scheu said.
“The URETEK technology stabilised the subgrade under the bridge to prevent future sinking. It was also used to jack up the bridge and reduce the deflection by about 50 per cent.”
“In the interest of minimising disruption to local residents, we managed to ensure the bridge remained open to traffic during works by keeping one lane open under traffic control,” he said.
Once the subgrade had been stabilised, reinforced concrete slabs were constructed between the box culvert legs in the two cells north and south of the central cell. These slabs were tied into the box culvert legs and also tied to the existing cut off walls upstream and downstream of the bridge.
“The slabs will provide structural stability for the box culverts and minimise the risk of subsidence in the future.”
The damaged reinforced concrete deck was then removed with a profiler. The ‘white rock’ subbase (between the top of the box culverts and the underside of the deck) also had to be removed due to water damage.
Replacement concrete work was carried out by local company Tony’s Concrete and Kerb of Goondiwindi and was completed in September 2012.