Better Roads Digital Magazine
Issue link: http://read.dmtmag.com/i/165348
paving speeds up delivery, eliminates a significant amount of surveying and staking and improves paving accuracy. "For a paving engineer who has tripped over his share of stringlines during the years, this was nothing short of revolutionary," Riley says. The stringless machine control system regulates the steering, grade, draft and crossfall of the paver. The system guides the paver in relation to a digitized 3D model of the highway, running on a computer on-board the paver. The paver is equipped with two prisms, mounted on the machine, as tracking targets for two robotic total stations. When setting up the robotic total stations, a technician back-sights each of them to four known control points. That fixes the location of the total stations relative to the digital model. The two total stations follow the movement of the two prisms on the paver and communicate to the machine computer the paver's precise location via radio link. The machine computer then computes the differences between the paver's actual location and the digital terrain model. Knowing those differences, the machine computer instructs the paver to regu- late the machine in the X, Y and Z directions automatically. Two additional total stations are set up, one ahead and one behind the paver, to use in checking the new pavement. As the paver passes the next total station in front of it, the crew moves the rear station around in front. That way, the crew "leapfrogs" the total stations down the highway – and the paver never needs to stop. Even in traditional stringline paving, stopping the paver is highly undesirable for mainline paving, as it typically introduces a bump in the surface. "It was phenomenal – pretty amazing to me," Cheney says. "I'm an old curb-and-gutter man, and we would always use stringline, so I was somewhat apprehensive. On another IDOT project, we used the stringless control system, and the next day, IDOT was there with a group of surveyors. The slab elevation was amazingly close, like the thickness of a driver's license. It was right on the money." The challenge of the project, Cheney says, was matching new asphalt shoulders that IDOT had placed the year before. "This is a true concrete 'mill-and-fill' project and the first of its kind in Illinois on this scale," Riley says. From roadways to walkways, saFety starts at the surFace. SafeLane® surface overlay The 4-inch concrete overlay was paved in just eight days SafeLane® surface overlay is a vital anti-icing tool in the battle to prevent ice and frost from forming on walkways, roadways and bridges. The patented technology retains deicing chemicals within the surface and releases them as temperatures drop below freezing, helping to keep motorists and pedestrians safe from dangerous winter conditions. Pavement substrate Available in two compositions for vehicle traffic and foot traffic, drivers and pedestrians can count on SafeLane® surface overlay to improve traction and enhance safety. Call 1-866-900-7258, or visit www.cargillsafelane.com to learn more. A Cargill Deicing Technology Product Text INFO to 205-289-3789 or visit www.betterroads.com/info Untitled-4 1 HighwayCon_Illinois_BR0913.indd 15 Better Roads 8/26/13 9:18 AM15 September 2013 8/29/13 1:06 PM