Deformation Mechanisms in Uncemented Sandstone, Examples from Triaxial Tests

Deformation mechanisms in porous sandstone and sand are important for understanding the distribution of faults and their associated properties. Controlling mechanism during localization depends on stress history, burial depth and fluid composition, but also lithological variations like porosity, grain size and mineralogy. An experimental program is design to investigate the pressure conditions and mechanical constrain on localization of deformation structures with varying confining pressure in uncemented sandstone. A natural sandstone material from the Boncavaï quarry in Provence, France, where deformation structures are observed, has been selected for the tests program. In the experiments shear enhanced compaction and cataclasis are identified whereas identification of deformation bands is difficult.