Analysis of the historical collapse of an abandoned underground chalk mine in 1961 in Clamart (Paris, France)

In chalk mines, the method of room and pillar mining has been widely used in France. Yet, many large collapses have occurred during or after their exploitation, with the collapse of Clamart (south of Paris, France) being well known as one of the most catastrophic. Today, 50 years after the collapse, the main causes of the event are still not well understood. This paper presents a back-analysis of the case study, using both an empirical approach and a numerical approach. Based on a set of hypotheses, an empirical approach and 3D numerical modeling have indicated a plausible scenario that may explain the collapse: The large collapse may have been caused by a lack of bearing capacity of the pillars and the sudden rupture of a hard limestone bed on which the load would have accumulated until overload occurred. The bed weakness between the two mine levels may also have had an influence on the mine's general lack of stability. Moreover, under the given hypothesis, the study shows a very low influence of the water table due to flooding of the mine.