Project Profile: Guiding the Upgrade

May 1, 2011
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The National Road Authority in Ireland has a plan. It intends to upgrade the N18 Limerick to Galway Road to a new dual carriageway with hard shoulder. Lollygagging sheep beware.

Currently there is work being done on a 1,000,000-euro, 22-kilometer, dual carriageway scheme extending from Ballinger’s Corner, north of Gort, to Cragard, south of Crusheen, where it will tie into the existing N18 Ennis bypass. The project also includes 10 kilometers of local road realignment, 12 kilometers of accommodation access tracks, 14 new bridges, a grade-separated junction, and an at-grade roundabout junction.

The route selection, Environmental Impact Assessment, and roadway design were completed by Babtie Pettit Ltd. of Limerick, Ireland. The proposed road scheme was designed with the following objectives:

  • Alleviating traffic problems with respect to capacity and safety on the existing route
  • Accommodating traffic needs for the future
  • Improving access between Ennis, Limerick, Shannon, and Galway
  • Improving journey times for those using the N18 route
  • Improving traffic distribution on the road network of the area
  • Improving environmental conditions along the existing route
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Approximately 425 acres of land will be required for construction of the road, which is expected to take three years. The joint venture between Siac Construction, Dublin, Ireland, and the civil engineering contractor Wills Brothers Ltd., County Mayo, Ireland, was responsible for building the roadway.

Bardon Composite Pavements, Leicestershire, England, part of the Aggregate Industries group of companies, won the contract to mix and place 86,000 cubic meters of cement-bound granular materials (CBGM) for the base and complete the finished road surface with a blacktop that is bonded to the CBGM.

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“To supply the CBGM required, we put a production facility onsite to mix the raw aggregates for the 180-millimeter sub-base layer,” says Richard Needham, operations director for Bardon Composite Pavements. “This sub base is critical because it is the main load-bearing layer of the road construction.”

Siac/Wills JV Ltd. employed a fleet of tipper wagons to deliver approximately 500 tons per hour to the project site. Bardon Composite Pavements was responsible for placing 86,000 cubic meters of CBGM on the 11-meter-wide road and hard shoulder at a depth of 180 mm.

The company’s six-man paving crew used a Volvo Construction Ingersoll Rand ABG Titan 9820 paver, with its 13-meter-wide capacity, equipped with a Trimble PCS900 paving control system, to place the material.

Bardon Composite Pavements acquired its Trimble systems through Korec, the Trimble dealer for the UK and Ireland. “The Trimble PCS900 Paving Control System is a 3D automatic screed control system that allowed us to directly reference off the road design,” says Carl McCoiv, contract manager with Bardon Composite Pavements. “It helped us achieve a very smooth final paved surface with accurate material usage.”

Bardon uses a Trimble SPS930 Universal Total Station to guide the paver. “The Trimble SPS930 is accurate to 1 arc second in the vertical and horizontal angles, which made it ideal for this dual carriageway project where the accuracy tolerance was very tight,” Needham says. “By paving the base to design correctly the first time, we definitely saved on the cost of rework and additional material.”

Needham points out that the Trimble systems allowed them to pave in a stakeless environment and save approximately 50 worker hours per week. He reports that there is less surveyor time since there’s no need for placing pins and tape-everything can be captured with the Trimble SPS930 running SCS900 Site Controller Software, which captures and records the surface levels. “We’re doing the as-built survey as we go,” he says. “There’s no double work. The guys that are actually paving are doing the survey at the same time, and it’s all being recorded electronically.”

Needham continues: “We saved time and effort with setting and adjusting stringlines; plus, we weren’t allowed to put road pins in the verge side of the carriageway because of a surface-water channel design that has a membrane that cannot be pierced by a road pin. This was about 3 meters wide and had to be placed in front of the paver so the CBGM could be laid over the top and secure it in place. If we had to use traditional pins and tapes for our lever control, the offset of the tapes and the pins would’ve been over 3 meters, and it wouldn’t have been possible to maintain accurate level control. We used the total station system to eliminate the use of pins and tapes.”

The setup phase for the project was started in the autumn 2009, and Bardon Composite Pavements expects to have the CBGM paving completed by mid-June 2010. The company has been completing about 600 to 700 linear meters a day and anticipates being done a couple of weeks ahead of schedule.

“The feedback we’re getting from the end product is that everybody is over the moon,” Needham concludes. “The rideability, consistency, and reliability have everyone happy. With the Trimble systems, we’ve eliminated the need for rework; we’re getting it right the first time.”