Experimental Investigation and Constitutive Description of Mechanical Anisotropy in Soft, Porous Rock

The mechanical properties of Maastricht Calcarenite, a carbonatic sandstone with high porosity, are investigated through an extensive laboratory program. The mechanical response under different stress conditions, including compression and extension tests, is studied and the influence of anisotropy is investigated. The test results confirm that the mechanical behavior of the rock is highly anisotropic, resulting in a rotation of the yield loci. The strength and post yield behavior are also affected. The experimental results show that the brittle-ductile transition is independent of the bedding orientation and that the rock fails by the formation of discrete compaction bands in triaxial compression tests at high confining pressures. An analysis of a discrete compaction band on the microscale shows grain crushing. The data obtained in the laboratory is used for the calibration of a simple constitutive model using the projection method, which is then shown to capture anisotropy in the mechanical response.