South-East Scanning was engaged to conduct a comprehensive subsurface investigation of the Anna Creek Bridge, a critical transport structure in regional Queensland. The bridge had shown signs of surface cracking and deformation, prompting concern from local engineers about the potential for internal voiding, slab delamination, or material degradation beneath the roadway.
Our Objective: Structural Integrity and Subsurface Anomaly Detection
ANNA CREEK BRIDGE
Our objective was to provide a detailed, non-invasive assessment of the bridge deck and supporting concrete structures to support maintenance planning and ensure continued structural integrity.
To execute the survey, we mobilised the **Mala GX160MHz ground penetrating radar (GPR)** system. This low-frequency antenna was chosen for its ability to penetrate deeply into reinforced concrete while capturing reflections associated with large-scale anomalies such as voids, delaminations, or significant material changes. The radar was mounted on a rugged cart and pushed along the bridge deck in a tightly spaced grid, with transect intervals of approximately 400 mm to maximise resolution.
All positional data was captured using the **Emlid Reach RS2 RTK-GNSS system**, allowing for centimetre-accurate georeferencing of GPR reflections. This spatial precision was essential for overlaying results onto bridge plans and drone-captured orthophotos.
Data was post-processed using **Geolitix**, a powerful cloud-based GPR processing and interpretation platform. We produced multiple depth slices and volumetric views of the internal concrete structure, with a focus on mapping high-amplitude reflection zones indicative of potential voids or internal separation. The ability to generate real-time depth plots and 3D anomaly volumes allowed us to visualise the internal behaviour of the deck in ways that traditional inspections could not.
What Happened?
The most significant finding was a consistent zone of high-amplitude, discontinuous reflections approximately 300–400 mm below the surface across a mid-span section of the bridge. These anomalies, confirmed across multiple transects and depths, suggested internal degradation likely due to prolonged water ingress and potential sub-surface erosion.
Deliverables included
- 3D depth models of the bridge deck with identified anomaly zones
- Depth-corrected heatmaps showing amplitude variation
- Drone orthophotos overlaid with GPR results
- A full interpretive report with recommendations for engineering follow-up
Outcome
The project enabled engineering stakeholders to transition from visual assumption to evidence-based understanding. The GPR results guided a targeted remediation plan focusing on the mid-span anomaly zone, preventing unnecessary full-deck replacement. The findings also helped justify further non-destructive testing using ultrasonic echo for deeper confirmation.
This project demonstrated South-East Scanning’s capability to deliver high-resolution GPR modelling in complex structural environments and reinforced our role as a trusted provider for Queensland’s regional infrastructure sector. To get in contact with us, reach out to our friendly team so we can help you with your projects!
