Briswest Precinct 6 | Case Study

Briswest is one of South East Queensland's largest industrial estate developments. Precinct 6 required expert remediation of Newhill Colliery Cochrane Seam mine workings to prevent subsidence for upcoming warehouse construction.

The site consists of fill and residual soils overlying Triassic Ipswich Coal Measures. The mine workings feature a nominal 6m bord width at depths of 25m to 50m, with a seam dip of 14 degrees.

Geotechnical assessments confirmed that cover depths were insufficient to prevent sinkhole propagation. Additionally, the presence of flooded mine entry tunnels required a specialized, high-effectiveness void-reducing solution.

We implemented a targeted grout cone strategy, constructing 12 cones at critical intersections. This approach ensures any potential roof failure event would self-choke, maintaining surface stability.

A rigorous quality assurance programme included camera verification of cone geometry and 189 Unconfined Compressive Strength (UCS) tests. These results confirmed the grout met the minimum 5 MPa strength required for durable mine void fill.

DGSA successfully completed all 12 grout cones, eliminating the identified sinkhole risk and satisfying all geotechnical requirements. The project was delivered with zero recordable safety incidents, allowing Rogan Development Solutions to proceed with site construction.