Unsaturated rock mechanics applied to a low-porosity shale

This article presents the results of tests carried out on partially saturated shale samples: a water retention curve was measured, and the evolutions of mechanical properties (uniaxial compressive strength and tangent modulus) with suction were studied by means of uniaxial compression tests. The originality of this experimental programme lies in the use of the osmotic technique in addition to the relative humidity control technique to impose suction on rock samples. The use of both methods allowed investigating a broader range of suctions (especially to reach higher degrees of saturation). Finally, the validity of an effective stress, similar to the expression proposed by Bishop for soils was examined for predicting failure under uniaxial compressive states of stress.