Large-Scale Mapping of the Historical Underground Limestone Quarries Using Mobile Laser Scanning, a Case Study in Riemst, Belgium

The cross-border Krijtland region in Belgium and the Netherlands encloses hundreds of historical underground limestone quarries. The municipality of Riemst, Belgium, is used as a case study because of the high density of underground quarries found there, and which are prone to frequent collapses related to the historical underground exploitation. As not all underground quarries have been mapped, a mobile laser scanner has been employed to aid the mapping surveys. This paper investigates how this method and its data can be used in the field of geoheritage and safety studies of underground quarries. The mobile laser scanner is an effective tool in mapping the vast underground networks, as well as georeferencing and mapping underground voids that are inaccessible for normal surveyors using a total station. The large amount of data, obtained by various surveys provides a high level of detail in which different structures and features can be identified. The results demonstrate the presence of different typologies of entrances, gallery morphologies and outlines in various underground quarries. It also appears to be a valuable tool in visualizing and identifying geological and stability features, such as karst, pillar instability and collapse areas. It can be concluded that in the field of safety management and geoheritage studies a mobile laser scanner proves to be an efficient method for mapping, documenting the underground landscape and describing different structural elements of underground quarries.