Influence of different cooling treatments on the mechanical properties of granite under Brazilian splitting test by grain-based model 3D

During the operation of an enhanced geothermal system (EGS), the reservoir rock undergoes different cooling treatments based on the distance to the surface rock. The tensile capacity of reservoir rocks is a key parameter in estimating the parameters of the hydraulic fracturing process. Therefore, the gain-based model 3D (GBM3D) was constructed to explore the micro behavior of granite under the heating/cooling process and the Brazilian splitting test. The numerical results demonstrate the ability of GBM3D to reproduce the grain interlocking and rotational resistance behavior, making it applicable to simulate the mechanical behavior of granite under uniaxial compression and the Brazilian splitting test. Temperature and cooling rates have significant effects on the stress-strain curves. With the increase in temperature, the curves after peak strength translate from brittle to ductile, and the turning point of water-cooled granite is lower than that of air-cooled granite. When more flaws are present in the specimen, micro-cracks tend to occur along the loading axial near the center of the specimen. This result can be used to explain the defect in numerical simulation, where cracks are easy to develop near the loading position under the Brazilian splitting test. This work can provide recommendations for hydraulic fracturing.