Levelling Hunter’s Expressway

Completion is expected at the end of 2013.
The work has been let in two contracts:

  • Eastern section (F3 to Kurri Kurri), undertaken by the Hunter Expressway Alliance (comprising Roads and Maritime Services [formerly Roads and Traffic Authority], Thiess Pty Ltd, Parsons Brinckerhoff and Hyder Consulting).
  • Western section (Kurri Kurri to Branxton), undertaken by Abigroup Contractors Pty Ltd under a design and construct contract.

The Vermeer T1255 Terrain Leveller is working on the eastern section, with its owner Trenching Systems Australia (TSA) being initially hired to excavate Cut 13.

The rock in the cut is slightly weathered massive sandstone with some bands of conglomerate, and hardness is 30 to 40 megapascals (MPa). There are few defects.

The shallow depth of the cut (less than three metres) ruled out blasting, while the rock was too hard for ripping.

The production rate of around 40m3 to 60m3 per hour is comparable to production rates expected of blasting and ripping in this type of rock, and the Terrain Leveler has fitted seamlessly into the earthworks programme.

The cut rock is taken directly to fill locations where it is used as upper zone (300mm depth) base material immediately beneath the designed pavement. The excavated material is watered before it is picked up and transported, to control the moisture level.

A feature of the Vermeer Terrain Leveler is its ability to cut to close tolerances, with the ability to alter the depth of cut as well as the drum angle. This makes it an ideal machine to use with 3D GPS control. The ability to vary the depth of the cut provides some control over the size of material produced, with deeper cuts producing smaller material.

As a result of its performance in Cut 13, the use of the Terrain Leveler has been extended to base excavation in Cut 16. This cut has inter-bedded sandstones, siltstones and mudstones; the rock is slightly weathered and its hardness is 20 MPa to 50 MPa.

There are more defects than in Cut 13, with these occurring every 100mm to 300mm. Cut 16 is a deeper cut than Cut 13 and blasting will be used, with the Terrain Leveler used to excavate to within 30mm of the design level.

TSA is responsible for the Terrain Leveler?s set-up and operation. The main adjustments required were a slower drum speed to better match the rock, and tweaks to increase the dust extraction system?s effectiveness. The Terrain Leveler was productive from the outset. Use of consumables is modest: around five picks are changed each day.

David Wheatley, earthworks senior project engineer for the Hunter Expressway Alliance, believes that the current limit to wider use of Terrain Levelers in civil projects is their availability in the hands of subcontractors.

?I would look at using this piece of plant as an option in all cuttings,? Wheatley said.

Apart from applications in trimming to level and undertaking shallow cuts, Wheatley adds: ?The Terrain Leveler could be the most productive way of mining a cut of any depth for other reasons, such as distance to sensitive receivers.

?Vibration and noise restrictions at these receivers may require the use of a Terrain Leveler over traditional methods of drill and blast or rock hammering.?

Vermeer?s mining services national manager Craig Batten believes that the supply issue is improving, stating, ?TSA has taken delivery of a second Terrain Leveler, which is a huge endorsement of their performance.

?We have fielded other inquiries, and are confident that the size of the contracting fleet will increase. We also feel that the new T1655 (nearly twice the size of the T1255) has applications in civil construction as well as mining, and this could change the economics of using a Terrain Leveler significantly.?

Source: Vermeer Sales & Service

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