Trenchless Civil, a new face on the Australian trenchless scene, has the capability to install pipelines in sizes up to DN2,500 mm in variable ground conditions. Trenchless Civil has the backing and resources of a major Australian Civil Contracting Group.
Laverton Creek Drainage Scheme
Trenchless Civil is constructing a major floodway for Melbourne Water as part of the Laverton Creek Drainage Scheme. This includes pipe jacking seven DN1,650 mm concrete pipe culverts under the Melbourne-Ballarat rail corridor, operated by V/Line. Each culvert is 50 m in length, running parallel within 1 m of each other. The depth to pipe crown below the railway is approximately 5 m.
The geology consists mainly of high-strength to extremely high-strength basalt with occasional gravel and clay bands, requiring a tunnel boring machine (TBM) with closed face capacity. Trenchless Civil is utilising its MTS slurry TBM with earth pressure balance (EPB) capability, with the addition of a rock cutterhead that has been manufactured specifically to suit the anticipated geology. The system is proving highly successful with average advance rates of over 30 mm per minute achieved. Cutter wear has also been limited with cutter changes occurring after every second tunnel drive.
Trenchless Civil has liaised closely with V/Line throughout the project. The rail corridor being worked under enables high speed transport between two major Victorian centres, and therefore it is vital this service is not disrupted. As an added precaution, pipe jacking under the rail lines has been undertaken outside train operating hours. Stringent survey monitoring has confirmed no settlement of the tracks has occurred due to the tunnelling operation.
The successful running of the project has enabled each bore to be completed within a week and the tunnelling component of this project is anticipated for completion in early December 2012. Remaining works to construct concrete headwalls and finish floodway excavation are due for completion in April 2013.
Timbertop Outfall Sewer Project
Trenchless Civil has recently commenced works associated with the Timbertop Outfall Sewer Project for South East Water in Officer, Victoria. This project requires the installation of approximately 1,500 m of HOBAS sewer pipe of size DN300 to DN550 mm, with individual bore lengths of 130 m. Shallow grades of 1:500 along the alignment consisting of saturated sandy clays are expected to provide challenging conditions for the project.
A second pipe jacking frame has been fabricated specifically for this project, enabling the non-restrained joint HOBAS pipes to be pushed from the retrieval shaft as the drill rods are removed from the launch shaft. This is essential to maintain the integrity of the pipe string, given the possibility of ground collapse throughout the alignment.
New investments
Trenchless Civil has also recently invested in a Vermeer Axis guided boring unit, capable of installing on-grade pipelines to DN600 via vacuum extraction technology. Bores of up to 150 m in length can be achieved whilst maintaining exacting tolerances, through a variety of ground conditions from hard rock to saturated sands.