Modelling the field behaviour of a granular expansive barrier

The large scale “Engineered Barrier” (EB) experiment, performed at the Mont Terri Underground Laboratory is described. A coupled hydromechanical model is then used to simulate the test performance. Constitutive parameters for the bentonite granular backfill are based on experimental work described in a companion paper. An elastoplastic model describes the granular fill, while the host rock is simulated by a damage model. Predictions of EDZ development around the tunnel are compared with some indirect measurements. Calculated evolutions of relative humidity and stresses within the buffer are compared with sensor records. Good agreement was found for the bentonite blocks supporting the canister. The granular expansive fill exhibit a more irregular behavior. Calculated displacements of the canister agree in absolute terms with actual measurements.