Abstract : Modelling of deformation, rupture and fracturing of rocks is a major challenge in many scientiﬁc and
practical ﬁelds, especially for fractured reservoir production. However, this modelling is harmed by poor knowledge of the constitutive laws. Therefore experimental approaches, and in particular physical modelling, that is the subject of this work, are of great importance.
We developed an innovative technique of such a modelling, based on a new material, Crack1 which is
physically scaled to a typical reservoir rock, a limestone. An extensive experimental program has been conducted, using a polyaxial device. This device combines both simplicity and eﬃciency, in particular in reduction or complete removal of the friction along the model boundaries. The main results can be summarized as following :
(1) Joints networks has been reproduced for the ﬁrst time under homogeneous loading. (2) Joints form under triaxial compression and therefore they are not Mode I fractures. (3) Fractographic patterns on natural and the model joint surfaces are similar, implying that the physical similarity is observed both at micro- and macro-scale. (4) Joint spacing S does not depend on the model thickness, contrary to the widely adopted “saturation”concept. S was shown to be controlled by the stress state and the accumulated deformation. (5) We also reproduced fracture corridors, whose formation is controlled by the rigidity contrast at the model boundaries. (6) The increase in the mean stress σ results in the change of the fracturing style, which changes continuously from jointing to shear fracturing. (7) Based on the bifurcation theory, it was demonstrated that this transition is controlled by the reductionof the dilatancy factor β with growing σ.
These results thus conﬁrm that constitutive laws directly control the fracturing. More extensive accurate investigation are now needed to better constrain these laws.