Southern Downs Repa Projects 2022 – Kital Bridge Remediation

Kital Road Bridge is located 5.8km from the New England Highway, and consists of prestressed TMR bridge planks transverse stressed over a 21.9m single span across Dalrymple Creek, Southern Downs. The abutments consist of precast concrete abutment with 45degree wings, which sits behind the abutment headstock supported on 3, 400×400 precast concrete piles, driven to a founding level of 85.16 and 84.5 for abutment A and B respectively.

Each end has a concrete instu approach slab approximately 3m long with bevelled thickening at the abutment end. It services SM1600 traffic loads with a design speed of 100km/hr. The flood resilience is < 10% AEP. The bridge suffered sever damage in early 2022 being overtopped and assessed in May 2022 (refer photos).

1. The bridge was overtopped and broke the banks of Dalrymple Creek. As a result the fill material behind the abutment headstocks and wings fluidised and dispersed causing undercutting to the approach slabs and delaminating the bitumen.

2. The lack of key of thickening to the flab slab design of the approach slabs offered little to no protection to overland flows, scouring out edges and undercutting the approach slabs.

3. Embedded barrier posts where appear to have be installed outside the pavement footprint and so scouring left posts unsupported and as a result the approach barrier has failed.

4. Photos taken 5/5/22 show delamination of wearing course from the pavement layers, which is consistent with other failures where overland flow soaks the pavement and creates a break in the bond between wearing course and pavement. Resulting in delamination.

TEG was engaged to provide expert advise and to design full remediation and sketches to remediate the bridge with a provision for additional resilience. Prepared reports including Risk. The engagement involved the following stages for the REPA project.

• Prepare a damage assessment and remediation report, defining the cause of damage and recommendation with sketches to remediate the bridge.
• Provide methodology for remediation repairs and budget costings for the repair scope specified.
• Undertake inspections during construction and address all RFI’s and issues to ensure continuity of remediation work.
• Prepare Construction Assessment report involving the collation of all site documentation, reports, tests and material deliveries to ensure that all works were accounted for and acquitted.
• Provide final certification of works.

The project was completed with specified time frames and for budget estimates, the bridge is now open and has a an improved level of resiliency requested by client.

Sean Edwards accredited with IPWEA recognised Professional Certificate in Asset Management Planning.