Starting signal for renovation of the Lueg Bridge
December 20, 2023 | Lucia Reinsprecht
The conditions of the facilities and the bridge itself have always posed a major challenge in terms of operation and maintenance. A large part of the structure runs along a slope that is up to 50 degrees steep and at risk of falling rocks,” says Felbermayr site manager Markus Winkler, describing the conditions on site, which also pose a particular challenge for the work on the maintenance road.
Rockfall jeopardises construction work
“The area below the bridge is largely a restricted area due to falling rocks,” explains Winkler. Extensive rockfall protection measures were therefore necessary before work could even begin on the path. It took almost eight months to install a 1000 metre long and up to eight metre high rockfall protection fence directly on the embankment. In addition, a 2000 metre long roll-off protection fence was installed and around 5000 square metres of rock netting were installed. A total of 500 helicopter flights were needed to bring materials and equipment to the area, which was difficult to access in places.
Around 20 specialists from Felbermayr Specialised Civil Engineering were deployed to install the protective shoring. Around 9000 metres of rock nails were drilled into the rock to anchor the safety measures in the slope. A tightrope act that the experienced skilled workers mastered with aplomb.
Extensive subsoil investigations
Extensive subsoil investigations are also an important part of the planning for the general refurbishment. “We are drilling at depths of up to 130 metres in some places,” explains Winkler, adding that the boreholes are drilled at intervals of 30 metres. More than 50 boreholes provide information about the geology and show which securing options are to be selected for the renovation work.
Gradual progress
According to Winkler, it is a “step-bystep” progression with constantly changing circumstances and correspondingly new requirements. As blasting directly under the motorway bridge is hardly possible, the rock material is removed mainly using excavators “reinforced” with hydraulic chisels. The up to ten metre high embankments in the construction of the service and maintenance road, which runs along the up to 55 metre high bridge piers, are to be stabilised with up to 30 metre long bar anchors and micropiles. The path embankments on the steep slope are being secured with nailed shotcrete walls. Around 2300 cubic metres of sprayed concrete and 40,000 linear metres of nails will be used. “More than half of the path has already been completed,” explains Winkler in awe of his employees’ achievements and confident that this particular job will be finished on time. It should also remain accident-free. Certainly extensive measures are being undertaken to ensure that this is the case.
