Overview of CFMS guidelines for the engineering design of underground structures built in swelling soils

When unloaded, saturated deep clay soils can be subjected to volumetric expansion, which causes significant problems in the design and construction of certain structures such as tunnels, deep excavations, and raft foundations. These deformations typically evolve progressively over the lifespan of the structure. The presence of swelling soils raised substantial concerns during the Grand Paris Express project, leading the CFMS (Comité Français de Mécanique des Sols et de Géotechnique) to establish an expert panel tasked with formulating recommendations for the characterization and management of these problematic soils. Subsequent to the publication of the recommendations, this paper offers a concise synthesis intended to facilitate a rapid comprehension of their content, written by some members of the working group.