Observations on cracking related to cuts into a valley: The "Brillants" underground quarry (France's Hauts-de-Seine Department)[Observations sur la fracturation liée à l'incision d'une vallée : Carrière souterraine des Brillants (Hauts-de-Seine)]

The study of a former underground chalk quarry at Meudon (the "Brillants" site), southwest of Paris, has indicated the presence of two main fracture families. One is attributed to the influence of a valley excavation located in the immediate vicinity of the quarry. The frequency of these fractures increases near the slope; the dip of their median part rises with the spot height in the rock block. The movements observed along these fractures reflect a centimeter-long displacement of the upper compartments in the direction of the valley. Identical observations on the fracturing of the slope in areas of limestone quarrying in the Paris region show that stratigraphic joints, at sufficient depths, have served to facilitate development of this type of fracture. A numerical modeling effort has revealed the difficulty involved in reproducing the formation of these fractures using both the current topographical profile and the mechanical characteristics of the block, even reduced, subsequent to a period of creep. The role of stratigraphic joints at the origin of these discontinuities still needs to be clarified.