Effects of temperature, pressure, and hydration on the microstructural characteristics and mechanical properties of calcite.

Geotechnical geological disasters occur frequently in China. Especially under complex environmental conditions, the failure mode of rock and the change mechanism of its mechanical properties are not clear. Although some progress has been made in recent studies on the physical and chemical properties of rocks and the microscopic mechanism of action, there is still a lack of systematic understanding of the change mechanism of calcite under different temperature, pressure and humidity conditions. In this paper, the influence of these environmental factors on the expansion behavior and elastic modulus of rock is deeply analyzed by constructing a calcite supercell model. The results show that the lattice parameters a, b and c of calcite increase by 0.45%, 0.45% and 0.44%, respectively, when the temperature increases from 300 K to 1000 K. At the same time, the bulk modulus, shear modulus and Young's modulus decreased by 6.45%, 3.63% and 3.92%, respectively. When the pressure increases from 0.1 GPa to 0.5 GPa, the volume of calcite crystal decreases by 1.10%, while the bulk modulus, shear modulus and Young's modulus increase by 2.74%, 9.36% and 8.66%, respectively. The bulk modulus, shear modulus and Young's modulus decreased by 15.6%, 18.5% and 18.1%, respectively, when anhydrous calcite was transformed into 50 water molecules. This study clarifies the degradation mechanism of calcite under the action of temperature, pressure and hydration, and provides an important theoretical basis and guidance for the prevention and control of geotechnical geological disasters.