The Application Of Permanent Shotcrete And Sprayed Membrane In Soft Ground Tunnels

Short and variable profile tunnels such as cross passages and Y-junction caverns in soft ground require an open faced
‘mined’ tunnelling approach. Traditionally these mined tunnel approaches relied on forward support and temporary
shotcrete with a second pass permanent concrete lining. Advances in forward support, shotcrete and membrane technology has enabled contractors to utilise shotcrete as a permanent lining element in soft ground and low cover environments that have greatly reduced overall construction duration and surface impacts. A number of smaller tunnel projects have recently been built in Australia utilising shotcrete as the permanent lining with extremely shallow cover.

The paper focuses on the innovations and experiences gained in adopting this type of approach from the perspective of the tunnelling contractor.