More room on the construction site
Traditionally, slipform pavers are controlled by mechanical scanning of previously installed stringlines. In contrast to this, when using a virtual stringline for 3D control, the height and positioning data for the line to be paved are contained in a digital terrain model. Two prisms are typically installed on the slipform paver, both of which have line-of-sight contact with a total station and reflect its laser beam. The total station determines the position of the prism in three dimensions and transmits it to the machine’s control system. In combination with the inclination sensors on the machine, this enables extremely precise control of the paver’s height and position.
In comparison to control by a physical stringline, the virtual stringline offers a number of benefits: The paving crew on the Ruta 5 highway was able to move freely around the construction site, and there was more room to manoeuvre the machines and construction vehicles. At the same time, the drivers of the tipper trucks delivering the concrete didn’t need to think about a stringline being in the way. They were able to drive right up to the slipform paver to offload the concrete anywhere on the site. Time-consuming detours to avoid the stringline when leaving the site were also no longer necessary. Apart from the better site logistics, the project managers also made a special mention of the outstanding IRI they were able to achieve with the system. The International Roughness Index (IRI) describes the evenness of the road surface.