Experimental studies on hydro-mechanical properties of metamorphic rock under hydraulic pressures

Abstract

The research on the hydro-mechanical coupling of metamorphic rock is of great importance in rock engineering. The main purpose of this study was to investigate the hydro-mechanical properties of metamorphic rock based on the experimental data from triaxial compression tests. Metamorphic rock samples taken from an underground oil storage facility were tested under different hydraulic pressures using a rock servo-controlled triaxial rheology test system. The results indicated that hydraulic pressure had impact on the strength, deformation and permeability of the metamorphic rock. Based on the test results, the stress-strain behaviour and permeability evolution of the rock samples show three stages. The mechanical properties of the metamorphic rock are presented in detail for the three stages in the whole stressstrain process. The derived mechanical parameters are correlated to the division of the phases. The relationship between hydraulic pressure and axial strain, lateral strain, volumetric strain and permeability are analysed and discussed, especially the influence of hydraulic pressure on various parameters in the hydro-mechanical process. The influence of the hydraulic pressure on the failure mode of the rock under coupled conditions is described.

Permeability Evolution of Granite Gneiss During Triaxial Creep Tests

“…At this stage, the permeability increases rapidly and the rock seepage The permeability evolution in creep tests under different pore pressures shows a phase characteristic, which is similar to the results obtained by Zhang et al (2015b). Based on our previous test results for granite gneiss in triaxial compression tests (Liu et al 2016) and the results of this study, the permeability evolution is associated with microcrack development during the process of rock deformation and failure. This change in permeability in a compressive state has also been demonstrated by many other investigators (Zoback and Byerlee 1975;Kranz et al 1979;Dong et al 2010).…”

“…Moreover, the strength of the granite gneiss is high. Liu et al (2016) showed that the peak strength of granite gneiss under a confining pressure of 4 MPa in triaxial compression tests increased from 213.22 to 237.13 MPa when the pore pressure decreased from 3 to 1 MPa.…”

“…According to Jiang et al (2010), permeability change is closely related to the density and opening of microcracks within the material. Liu et al (2016) described the changes in permeability throughout the entire stress-strain process and discussed the relationship between hydraulic pressure, strain and permeability. However, the variation in the permeability during rock creep deformation is not yet well understood.…”

Subsidence Mechanism and Stability Assessment Methods for Partial Extraction Mines for Sustainable Development of Mining Cities—A Review

“…Recent research also showed that the mechanical properties of rock material (e.g., rock strength, rock stiffness, the fracture toughness of rock, the elastic modulus of rock, etc.) may degrade due to water [110][111][112][113][114][115][116][117][118][119][120]. Poulsen et al [121] suggested that the strength reduction of saturated coal pillars can be estimated by the average strength reduction of all the lithological components of coal.…”

On the Relationship between Creep Strain and Permeability of Granite: Experiment and Model Investigation

“…These fractional derivatives-based creep models are clarified to be more accurate in reproducing the creep phenomena of materials with fewer parameters due to explicit mathematical expression [16][17][18][19][20]. It is notable that, most of above creep models are one-dimensional, however, Liu [21] pointed out that the permeability evolution of granite is related to the volumetric strain in the creep process. Therefore, in order to build a bridge between the creep strain and permeability, further studies of the fractional derivatives-based model considering damage evolution should be conducted targeting its three-dimensional form.…”