PENETRON System Beats Mud and Contamination: Burrows Road Tunnel
Part of the new Ausgrid (formerly Energy Australia) network from the nearby Beaconsfield South Substation, the Burrows Road Tunnel is 87m (285 ft.) long and 2.8m (9 ft.) in diameter. The construction project called for a trenchless, watertight tunnel to carry 6 x 132kV cable circuits under Burrows Road in the inner Sydney industrial area of Alexandria.
Abergeldie was appointed by Ausgrid to construct the watertight tunnel; a trenchless pipe-jack method using an Earth Pressure Balance Machine (EPBM) was chosen to dig out the tunnel. The EPBM tool was upgraded from 2.1m to 2.8m to cut the specified tunnel diameter.
However, with soil rank containing two centuries of industrial contaminants and so saturated with ground water, an on-site detention system was set-up, water samples taken and analyzed, and disposal of contaminated water arranged. This strict monitoring process, carried out in a restricted space, meant only that a limited volume of water could be stored; a regular rotation of collection trucks was necessary. The launch and receive pits were sunken eight meters into the contaminated soil. The project also included outfitting the tunnel with cable support brackets, and refitting the pits, for later use as tunnel maintenance access points.
Finally, 28 liner segments, 2.8m in diameter, 410mm thick, and 3m long, were pipe-jacked to construct the watertight tunnel. The actual tunneling process took 10 days at an average rate of 8.4 meters per day.
“The dimensions, location and soil conditions presented extremely difficult technological challenges,” explains Jozef Van Beeck, International Sales & Marketing Director of PENETRON. “Innovative engineering solutions were developed and implemented to address problems presented by the unstable, water-charged soil conditions.”
Working together with PENETRON Australia, the tunnel design consultants (Demlakian) and Abergeldie chose the PENETRON system to provide a watertight structure that met with the client’s (Ausgrid) requirements. PENETRON ADMIX was used for all concrete elements within both the launching shaft and the receiving shaft to protect against water ingress under the extreme conditions found at the site. All construction joints and pipe penetration within the shafts were sealed with PENEBAR SW waterstops, the formed tie holes were filled with PENEPLUG and PENECRETE MORTAR.
“Even with the exceedingly difficult soil conditions and high water saturation levels, the PENETRON system proved to be extremely effective at resisting water under pressure and an ideal solution for this watertight tunnel construction,” adds Jozef Van Beeck. “Our success with the Burrows Road Tunnel confirms just how effective PENETRON’s permeability reducing technology can be, even in demanding high hydrostatic conditions.”
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