Newcastle Chapter

Grouting at Ipswich and Hunter Expressway

Bill Holz & Iain Robertson

Abstract – Part 1 – Ipswich Motorway, Bill Holz

The upgrade of one of Queensland’s busiest road transport corridors, the Ipswich Motorway, between Dinmore and Goodna by the Queensland Department of Transport and Main Roads (DTMR) involved re-aligning the motorway corridor over two separate abandoned coal mines and adjacent a third.

During the preliminary site investigation and through the early stages of design, abandoned 19th Century coal mines were discovered under sections of the footprint of the new motorway. Whilst there was knowledge of the existence of these mines, details as to size, depth and accurate location were largely unknown.

The mines varied in depth from 20m to 90m, with workings in one or two seams. The conditions encountered included workings: filled with water, filled with methane, and varying from open to fully collapsed. Keller Mine Fill undertook the filling of the mines using state of the art drilling and filling techniques. A substantial mine investigation program using cameras, sonar, and inclinometers to aid targeted drilling improved confidence in the filling techniques.

Part 2 – Hunter Expressway, Iain Robertson

This $48M sub alliance involved mine filling at depths of up to 120m, 145,000m of drilling, and 200,000m3 of grout injection. The mine fill project at the Hunter Expressway represented one of the largest and most challenging mine fill projects carried out to date. Some requirements of the project, such as environmental restrictions and hilly terrain, stretched what might have been considered practical and the successful completion of the work provides a useful benchmark of what can be done within reasonable commercial constraints. Activities that were stretched include:

  • Drilling technology and capability
  • Pumping methodology
  • Data acquisition
  • Validation

Engineers Australia members participating in AGS technical sessions can record attendance on their personal CPD logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.