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Albert trench 24 Jan 2018.JPG

Videos: See inside the CRL tunnel trench



Construction has started on Albert St’s first CRL tunnel box.

CRL contractor Connectus JV has started the base pour for the first of the 29 box sections of the tunnel.

The process of building the tunnel box sections involves a number of steps:

  • A smooth surface needs to be constructed along the pile line, against which the tunnel walls can be poured. Steel mesh and pins are installed into the piles, followed by a sprayed concrete application known as ‘shotcreting’. The shotcreting team has already completed the first 44 metres section of the shotcrete surface.
  • A base ‘blinding’ layer is poured to form a level and clean working surface. The first 44 metres of blinding has also been completed.
  • Waterproofing membrane is then hung against the shotcrete surface and laid across the blinding layer.
  • Steel reinforcement will be tied and formwork (temporary moulds into which concrete will be poured) installed as the pouring of the tunnel boxes progresses.

For the first concrete pour for the base slab of the tunnel box, the job required; about 15 workers, 25 concrete trucks and 109m3 of concrete. Today the team removes formwork and prepares the construction joints.

Albert concrretew pour 8 March 2018.jpg

Videos - inside the trench

These steps will be followed until 350 metres of CRL tunnel is constructed down Albert St.  

At the same time as the first pour, other works were going on:

  • Fixing steel on slab 3
  • Shotcreting on slab 5
  • Lifting into the trench to install walers & struts at slab 8
  • Rock bolting on slab 10
  • Excavation and spoil removal  from slab 12-19
  • Service relocation at slabs 21 to 24

Working in the middle of the road in the CBD, and the excavation taking up the entire footprint of the site makes for many logistical challenges. We only have about 6m of temporary decking over the top of the excavation for all materials, plant and equipment to come and go from site. This space must support many of the following pieces of plant excavators, trucks for spoil removal, concrete trucks, concrete pumps, shotcrete pumps, reinforcement delivery and cranes just to name few. When you include the people needed to run these operations and the lay down of materials it doesn’t leave much room for mistakes.
Prior planning between engineers, supervisors, foreman and work crews is critical to ensure a smooth-running operation and identify potential clashes and eliminate delays. Often a decision will have downstream influences on other activities so good communication and managing change is key. At the foremost to all our planning is providing a safe work place for all our staff and ensuring the public safety for those using the spaces around the site.”
— Thomas Jefferd, Connectus Tunnel Box Project Engineer

Bulk excavation of the cut-and-cover trench on Albert St continues towards the Customs St intersection.