Under the leadership of GEOTEST Ltd, the geotechnical, geological and hydrogeological foundations for the expansion and renovation of 31 kilometres of national road in the canton of Bern have been assessed.
The Swiss national roads are continuously and incrementally being renovated and widened on behalf of the Federal Roads Office FEDRO. For the planning stage of the three most recent sections (N1: Wankdorf to Schönbühl, Schönbühl to Kirchberg / N8: Spiez to Interlaken West), GEOTEST designed the foundations for the planned measures, concepts for the maintenance, and is supervising the implementation.
A comprehensive probing concept was necessary for the baseline survey. On the N1, various bridges had to be widened for the expansion, numerous retaining walls had to be replaced and newly built, and many associated measures, such as slope cuts and noise protection walls, had to be planned. For this purpose, the geotechnical-geological and hydrogeological foundations were surveyed directly on and alongside the national road and summarised in more than 60 structure-specific reports with technical construction-related conclusions and recommendations.
The section of the N8 along Lake Thun includes the hydrogeological-geotechnical ground work for the stability assessment of over 50 structures and retaining walls. In addition, in the section between Faulensee and Leissigen-West, local subsidence of the road has occurred repeatedly for years as a result of the underlying gypsum karst. Using a combination of pile driving, core drilling and geophysical methods (georadar and hybrid seismics), the rock surface and critical structures under the busy national road were localised. In this way, a geological model of the subsurface was created that can be used to localise karst cavities in the subsurface. Future renovation measures can thus be planned and implemented in a more targeted and economical manner.
For the survey of the geotechnical limiting factors, a total of 94 core drillings, 240 pile driving probes, and over 100 laboratory analyses were planned, supervised and evaluated for the three sections of the N1 and N8.