Two-component backfill grout system in double shield hard rock TBM. The “Legacy Way” tunnel in Brisbane, Australia

Abstract: The main purpose of the twin tunnels of the Legacy Way project is to connect the western freeway at Twoowong with the inner City Bypass (ICB) at Kelvin Grove, providing an alternative route to local roads for traffic. The project was awarded to the Consortium Transcity, including the companies Acciona, BMD Constructions and Ghella, which used a hard rock double shield TBM to excavate the 4.6 km twin tunnels. One of the main characteristics of the TBM was the use of the two-component grout to inject the annular void behind the tunnel lining, although rock TBMs generally use other systems of backfill grouting. The implementation of the two-component system made up of a cement grout (component A) and an accelerator (component B) mixed at the injection point will be described in detail in the paper.