Thermomechanics for Geological, Civil Engineering and Geodynamic Applications: Numerical Implementation and Application to the Bentheim Sandstone

Observations of the mechanical behavior of porous rocks subject to external loading indicate the existence of complex dependencies on the level of confining pressure, fluid pressure and rate of deformation. Due to the heterogeneous nature of porous rocks, their macroscopic response is the result of underlying microscopic processes which can alter the microstructural organization of the grain-pore network. The impacts of the multiscale and poromechanical behavior of geomaterials are relevant for a number of applications ranging from civil engineering, reservoir engineering, geological and geodynamic. The use of thermodynamic-consistent approaches to construct constitutive laws which span a large range of time scales is particularly relevant in this context. In this two-part contribution, we present extensions of the thermomechanics theory to account for the poromechanics of path- and rate-dependent critical state line models and we cover the relevance of this thermodynamic-consistent model for civil engineering, geological and geodynamic applications. In this second paper, we extend the thermomechanics theory to account for the poromechanics of geomaterials in agreement with the theory of poroelasticity and considering in addition dissipative inelastic processes. We illustrate using experimental data how the thermodynamic-consistent model derived can account for the macroscopic mechanical and porous responses in triaxial loading experiments. We particularly focus on the transition from dilation to compression regime with confining pressure and the resulting localization styles ranging from shear dilation to compaction bands.

Automated summary

Observations show that the mechanical behavior of porous rocks under external loading is influenced by factors such as confining pressure, fluid pressure, and deformation rate. The multiscale and poromechanical behavior of geomaterials is significant for various applications including civil engineering, reservoir engineering, geological, and geodynamic studies. The use of thermodynamic-consistent approaches is important in constructing constitutive laws that cover a wide range of time scales.