INFLUENCE OF INITIAL SUCTION ON VOLUMETRIC VARIATIONS OF A SPECIAL SHALE: 'SCHISTES CARTON'

Schistes carton are foliated, highly overconsolidated, dark marls, with a schistose aspect. Outcrops of this formation of the lower Toarcian, are frequent in the Northeast of France (especially in the region of Nancy-Lorraine). When intact, the ultimate axial compressive strength of this material is about 50 MPa. Conversely, when the covering layer is thin, these shales are weathered and their mechanical properties deteriorate sharply. Significant swelling problems due to modification of in-situ stress and weathering during excavation have been reported. Experiments have been carried out to study the influence of initial negative pore pressure and water content on volumetric changes of this material. (A) For the covering abstract see IRRD 881647.