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How to build a bridge

17 Jun 2019

The Reservoir team has achieved a Level Crossing Removal Project first, using the innovative ‘monopiling’ technique to lay the foundations of the new rail bridge.

Last week, work crews at the Reservoir level crossing finished building the bridge foundations that employed the monopiling approach.

Traditional rail bridge foundations consist of a cluster of smaller diameter piles below ground topped with a large concrete ‘pile cap’ to support each bridge column.

At Reservoir, monopiling means most of the bridge’s columns are supported by only one pile with no need for a pile cap. Each monopile is 2.1 metres in diameter – roughly twice the diameter of a standard pile – and drilled to a depth of up to 28 metres below the ground.

Monopiling is ideal for Reservoir’s soil and rock material and low groundwater table. Removing the pile cap from the process also allows for a minor reduction in time and labour.

As the piling concludes, the rest of the bridge and elevated station structure will take shape above ground for everyone to see.

The first of 32 piers are now sprouting atop the foundations. These will support the main bridge structure and the new Reservoir Station.

This graphic shows what you’ll see as construction on the new rail bridge and Reservoir Station continues.

Piling works at Reservoir

Graphic showing the stages of creating the rail bridge. Refer to text below for more information.

  1. Foundation works, known as piling, start by drilling holes as far as 28 metres deep.
  2. A cylindrical, steel reinforcement cage is inserted into the hole.
  3. The hole is filled with concrete to form a pile.
  4. The piers, or bridge columns, are built on top of the piles, starting with a steel reinforcement cage.
  5. A steel mould is placed around the cage.
  6. Concrete is poured into the mould and cured to create the pier.
  7. Pre-cast headstocks are delivered to site and installed on top of each pier. Headstocks support the bridge spans and transfers the bridge load to the pier below.
  8. The bridge sections, known as U-troughs, are made up of two L-shaped beams that are installed on top of the headstocks. The two beams are joined with concrete to form a U-shape.
  9. Steel beams are used in place of U-troughs over the High Street intersection due to the long span required to cross the road.
  10. Train tracks and ballast are laid.
  11. Signalling, communications and overhead power equipment is installed.

While all of this work is happening, there are changes to the way you travel and we ask you to continue to keep an eye out for those detours and all of the work happening.

Reservoir Station will temporarily close and buses replace trains on the Mernda line at various times in July and August.

In the meantime, check out the latest progress pictures at Reservoir or watch our video that explains the monopiling process below.

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