When a dense granular material with a viscoplastic matrix, such as ice, is submitted to uniaxial or triaxial compression, it is considered that one portion of its observed strength is due to the internal confinement resulting from tensile stresses generated in the matrix when it tends to oppose the dilation. Recently, a conceptual model of compression strength behaviour of such dilatant materials was developed by the senior author. This paper presents the model and describes an experimental study intended to check its validity. For this purpose, a series of triaxial compression tests on both frozen and unfrozen sand at carefully controlled densities was performed. The test results give a clear support to the theoretical predictions of the contribution of dilatancy hardening to the strength of a dense frozen sand.Key words: frozen sand, compression strength, triaxial compression tests, pore ice, cavitation, dilatancy hardening, conceptual model.