The Dutch province of Limburg is home to several marl caves, which have been dug out over the centuries by the local population. These days, the caves are a major tourist attraction, with over 300,000 visitors a year. The Municipality of Valkenburg a/d Geul wants to guarantee the safety of visitors at two of these caves: the Gemeentegroeve and the Sibbergroeve.
Fugro has been awarded a contract to install and maintain a system to monitor rock mechanical safety and subsidence in these caves. Working together with local marl experts, Fugro will install ‘state-of-the-art’ fibre optics sensors and cables, which are resistant to the extremely high humidity in the caves and are guaranteed to provide highly accurate measurements for the full 10-year monitoring period. Special care will be taken to hide cables and sensors so that they are barely visible and the historic character of the caves is preserved. Installation of the system began in July 2019.
The measurement data will be stored and presented in Gaia Insight, Fugro’s cloud-based data platform, providing all stakeholders with real-time access to the data.
Edo Noordermeer, Fugro’s Project Manager, commented: “The stability of the underground marl caves in Valkenburg is essential for the safety of visitors, as well as the infrastructure and buildings on the surface. With our state-of-the art monitoring solution, we will give the municipality of Valkenburg a real-time view of the safety status of the caves. With our system, the municipality will be able to take preventative actions before subsidence incidents occur”.