Four steps to Slab Track Austria
Slab production. Track laying. Surveying and fine adjustments. Concreting.
PORR’s precast slabs are produced with alignment design already integrated in them, so that on-site work is reduced to a minimum. The process follows a four-step approach.
Step one. Slab production.
Panels are produced in a prefabrication or field plant, and the precast panel production is therefore independent of weather conditions. Due to a complete quality assurance system, a constant high quality is guaranteed and documented.
The steel molds used for panel production are adjustable and can thus cover all track geometric curve elements without gaps required by a project. Each panel’s design takes the needs for possible reductions of the panel length, openings in the panel, coverings, dowels etc. into consideration. So the mold is set up in a way that ensures a panel design executed with millimeter accuracy.
Each of the slab types is unmistakably marked with a corresponding bar code and can therefore be easily identified at any time.
Traceability and information about the slab can be of great importance for production, installation and maintenance phase. This is why Slab Track Austria provides multiple ways of identifying the slabs to ensure specific design and manufacturing information is readily available. It is possible to collect and use information about the running line with the help of RFID chips. Additionally, slab labels provide important slab details without a need for an RFID reader.
Step two. Track laying.
Laying of the slabs is normally done with portal cranes. This enables the panels to be lifted forward in the smallest possible space. In addition, no reloading or intermediate storage is necessary, because the precast slabs can be taken directly from the transport wagon. In the case of discontinuous construction locations or missing track connection, the transport and the laying of the slabs by a truck with a loader arm is common practice.
Step three. Track surveying.
Installation of the slabs and calibration of the track can be done with and without the final rail in position.
Top-down installation method.
After installation of the laterally stored rails, the work of final track calibration begins by measuring the track position from top of the rail. Fine adjustments are done using threaded spindles applied to the slab. This method guarantees precise track set accuracy in setting the track with no further corrections required. Adjustment work is further reduced by the precise track geometry built into the precast panel. Therefore, calibration requires up to 50% less time compared to other slab track systems.
Installation and measurement without rails.
There are times when the rail material can be delivered to the construction site at a later stage, but the track construction needs to continue. In such a case very precise position of the integrated rail support points on the slab is used as the basis for surveying and fine adjustments. The rails can be installed subsequently when on the already built slab track.
Step four. Concrete pouring.
The self-compacting concrete grout is poured either directly or through a hose pump up to a maximum of 500 m, depending on the space available at the installation location. The use of a self-compacting concrete joint sealing compound enables an even and continuous embedding of the slabs. As a result of the vibration-free concreting process, the fine-tuning of the track unit is not affected. Furthermore, it is possible for the Slab Track Austria elements to be installed during a short railway traffic interruption due to the fast hardening process of the self-compacting-concrete. This was the case on the construction of the Lehrter Station, Berlin.