بررسي آزمايشگاهي تأثير دما بر خصوصيات مكانيكي و مكانيزم شكست برشي سنگ‌ كربناته

Rocks exhibit changes in physical an‎d mechanical properties under the influence of temperature, an‎d their failure mechanisms also vary accordingly. Among them, dolomite, as a low-permeability rock widely present in deep oil an‎d gas reservoirs an‎d nuclear waste disposal sites, follows this trend under high stress an‎d temperature conditions. Understan‎ding the effects of temperature an‎d confining pressure on the mechanical behavior of these rocks is essential for analyzing the stability of underground structures. In this study, the mechanical behavior of dolomite was investigated through Brazilian, uniaxial, triaxial, an‎d short-core compression (SCC) tests at temperatures of 25, 275, an‎d 525 °C. The Brazilian tests showed that the indirect tensile strength of dolomite increased with temperature, with approximately 52.4% an‎d 65.5% rise at 275 °C an‎d 525 °C compared to 25 °C. In the uniaxial tests, the average compressive strength increased from 86.5 MPa under ambient conditions by 31.33% an‎d 64.1% at 275 °C an‎d 525 °C, respectively. The elastic modulus increased by about 47.8% at 275 °C but decreased by roughly 6% at 525 °C relative to ambient temperature. Triaxial tests revealed that compressive strength rose with both confining pressure an‎d temperature due to microcrack closure an‎d structural compaction, while the elastic modulus showed an increase at 275 °C an‎d a decrease at 525 °C, likely due to the onset of carbonate decomposition an‎d thermal microcracking. SCC tests indicated that mechanical properties, including peak load, compressive strength, fracture toughness, an‎d shear stress, increased at 275 °C by approximately 19.8%, 18.9%, 19.9%, an‎d 11.4%, respectively, representing the highest enhancement compared to initial conditions. Further temperature increase to 525 °C led to decreases of about 0.8%, 1.7%, an‎d 2.5% in peak load, compressive strength, an‎d fracture toughness relative to 275 °C due to thermal degradation, while shear stress increased by 8.1% owing to surface roughness an‎d interlocking along the failure planes. Overall, the results demonstrate that the tensile, compressive, an‎d shear behavior of dolomite is directly influenced by temperature-induced microstructural an‎d physical changes. Moderate temperature increase up to 275 °C enhances strength an‎d fracture toughness, likely due to intergranular water loss, increased cohesion, an‎d microcrack interlocking, whereas higher temperatures induce local thermal damage, reducing mechanical performance. These findings are applicable in assessing the stability of nuclear waste repositories, geothermal projects, carbon storage, oil an‎d gas reservoir exploitation, an‎d the design of underground structures in high-temperature environments.

هاجر شرع اصفهاني , محمود بهنيا

عليرضا باغبانان , محمدرضا خان محمدي