Posted by: admin November 11, 2015

PROJECT DESCRIPTION:

Design and construction of an 87 m long pipe-jacked, hydrostatic tunnel to carry 6 x 132kV circuit cables through water-charged soil beneath Burrows Road to an Energy Australia/Transgrid Substation. The scope of works included intensive geotechnical and environmental investigations to inform detailed design, service location identification through potholing, design and shoring of the launching and receiving pits, tunnel boring, pipe-jacked lining, and fitting out of the pits to act as permanent access facilities for Transgrid maintenance staff.

Complex Challenges:

The entire tunnel lies below the ground water table adjacent to the Alexandria Canal, demanding innovative methods using hydrophilic crystals mixed with Bentonite to control groundwater seepage. Traffic management and staging of materials deliveries were also critical, due to the very tight site conditions, which provided little space for storage of materials awaiting installation.

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PROJECT DESCRIPTION:

Design and construction of a 2400mm diameter by 120m long pipe jacked tunnel, including fit out with stainless steel cable support brackets. The scope of works included construction of 8m x 8m x 8m deep cable pit which into which stainless steel access ladders and platforms were installed for continuing use by maintenance crews.

Complex Challenges:

The tunnel is located beneath railway lines and roads and has strict settlement and environmental monitoring requirements. Modifications to Abergeldie’s EPBM tunnel boring machine were required to suit the dimensions specified for the tunnel, and to address local soil conditions.

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PROJECT DESCRIPTION:

Design and construction of two pipe jacked tunnels: one through shale at Pymble 97m long and 1650mm in diameter a 33 kV cable circuit; and the other through sandstone at Artarmon 111m long and 1650 in diameter to carry a 132 kV cable circuit. The tunnels were bored beneath rail corridors, a major freeway and a watercourse.

Complex Challenges:

Restricted work area limited space for storage of pipe sections pending their jacking into place, requiring careful procurement and delivery scheduling, taking into account lead times for off-site manufacture. Mid-way through drilling of the Artarmon tunnel, the client called for a change to the depth of one section of the tunnel, requiring a sharp curve to be bored and lined.

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PROJECT DESCRIPTION:

Design and construction of two parallel pipe jacked tunnels, one 120m long and the other 54m, passing under two drains and a river. Abergeldie’s EPBM machine was used to bore the tunnels and jack into place segments of hydrostatic lining sleeve.

Complex Challenges:

Boring under sensitive waterways permitted zero subsidence of overlying soils, which varied greatly in consistency over quite short distances. Very tight alignment tolerances were specified, allowing only 50mm vertical variation and 100 mm horizontal. Actual alignment accuracy achieved was within <50mm.