Microgravity measurements (Mont-Aimé, 2021)
© BRGM
The need
There are traces of occupation at Mont-Aimé dating back to the Neolithic period. Many tourists visit this site, where occasional events are held. The aim of the BRGM study carried out between 2021 and 2022 was to improve knowledge of the underground cavities and archaeological remains in order to assess the risk of collapse and make them safe for visitors.
The results
BRGM applied and carried out various cross-cutting methods and activities:
- Research into the existence of cavities in written documents: the site has a wealth of history. There are several references to huge underground chambers;
- Aerial survey of cavities: the study included a LiDAR survey. This method eliminates the vegetation factor (a test of whether it could be applied in a permanently covered environment, such as the Amazon Basin). Analysis of the data (using semi-automatic processing) revealed more than 200 morphological features across the entire site, including 40 on or near the summit of the butte. Sixty depressions were checked in the field, seven of which were identified as possibly linked to cavities;
- Detection of cavities using geophysical and geotechnical methods: 15 negative microgravity anomalies were identified and checked by drilling 28 destructive boreholes (with camera inspections). No significant empty spaces were detected, but there are numerous non-compacted sections;
- 3D mapping and stability analysis of accessible underground cavities: two cavities (and man-made structures) were surveyed using a mobile laser scanner. By mapping them, we were able to correct the gravitational effect induced on the microgravity results and thus to highlight persistent residual anomalies, possibly linked to unknown cavities.
The conclusions of the study identified evidence of probable excavation on a larger scale than the chambers that can currently be visited, but on a much smaller scale than is referred to in stories and legends and mainly guided by fractures along ancient karst conduits.
General 3D view of objects surveyed by mobile laser scanner (shades of grey: surface; gradation in colour: depth underground) (Mont-Aimé, 2021)
© BRGM
Using the results
On the basis of the results of this study, the Agglo d'Epernay and the Bergères municipality will set up a risk management system linked to the underground cavities that takes their nature and the occupancy of the site into account, in order to ensure the safety of visitors. The results can also be used to promote the site's exceptional heritage.
BRGM helped us to carry out a LiDAR survey to obtain a topographic base and indisputable scientific data that will provide answers to the mysteries and deconstruct the myth of Mont-Aimé. This site has major tourist and landscape potential. On the basis of the knowledge we have acquired on the surface and at depth, we will be able to plan development work while preserving the existing site and managing the risk of collapse due to underground cavities.
The partners
- Agglomération Epernay Community, Coteaux et Plaine de Champagne (Hills and Plain of Champagne - Epernay Agglo Champagne)
- Municipality of Bergères-lès-Vertus
