“… Figure 9 The distribution of intragranular, intergranular and transcrystalline micro-cracks from simulations ( left , T = 200, 400, 600, 800 °C) and laboratory tests after heating–cooling process. ( right , T = 200, 400, 600, 800 °C, modified after 15 , 33 . …”
Section: Modelling Resultsmentioning
confidence: 99%
“…The average uniaxial compressive strength and Brazilian tensile strength of granite are 196.56 and 10.594 MPa, respectively. The macro and micro-mechanical properties of Yanshan granite were achieved from a series of Brazilian tests with temperatures 25–800 carried out by Guo et al 15 and Wu et al 33 . A typical SEM image of Yanshan granite after the Brazilian test is shown in Fig.…”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“…3 b. Figure 3 SEM images of Yanshan granite ( a ) at room temperature (25℃) and ( b ) after failure, modified after Guo et al 15 , Wu et al 33 . …”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“…5 ). Figure 4 Yanshan granite specimen for thermo-mechanical coupling test: ( a ) thermally heterogeneous specimen, ( b ) experiment after Guo et al 15 , Wu et al 33 . …”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“… Stress, force, AE rate and cumulative AE number-step or time curves from ( a ) the simulation and ( b ) the laboratory test at room temperature after Guo et al 15 , Wu et al 33 . …”
It is known that the heterogeneity caused by thermally induced micro-cracks and thermal stress can affect the mechanical behavior of granite. The laboratory-scale tests have the intrinsic limitation of non-repeatability and lack of effective methods to characterize the interaction effect between thermal micro-cracks and thermal stresses. In this study, we demonstrate how advancements in particle bonded model and moment tensor can help better understand the roles of high temperature in weakening granite and thermally induced cracking process in Brazilian test. Our results show that the types of micro-cracks (intergranular, intragranular, and transcrystalline ones) are related to their thermal expansion coefficients of mineralogical compositions. The intergranular tensile micro-cracks are predominant during the heating and heating–cooling processes. An obvious weakening of granite and non-central initiation is associated with the heterogeneity caused by the thermal damage and thermal stress. We also quantitatively evaluate the thermal damage based on orientation distribution, b-value, and nature of the sources, which gives a new microcracking perspective on tensile characteristics subjected to high temperature.
“… Figure 9 The distribution of intragranular, intergranular and transcrystalline micro-cracks from simulations ( left , T = 200, 400, 600, 800 °C) and laboratory tests after heating–cooling process. ( right , T = 200, 400, 600, 800 °C, modified after 15 , 33 . …”
Section: Modelling Resultsmentioning
confidence: 99%
“…The average uniaxial compressive strength and Brazilian tensile strength of granite are 196.56 and 10.594 MPa, respectively. The macro and micro-mechanical properties of Yanshan granite were achieved from a series of Brazilian tests with temperatures 25–800 carried out by Guo et al 15 and Wu et al 33 . A typical SEM image of Yanshan granite after the Brazilian test is shown in Fig.…”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“…3 b. Figure 3 SEM images of Yanshan granite ( a ) at room temperature (25 ℃) and ( b ) after failure, modified after Guo et al 15 , Wu et al 33 . …”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“…5 ). Figure 4 Yanshan granite specimen for thermo-mechanical coupling test: ( a ) thermally heterogeneous specimen, ( b ) experiment after Guo et al 15 , Wu et al 33 . …”
Section: Modelling Of Yanshan Granitementioning
confidence: 99%
“… Stress, force, AE rate and cumulative AE number-step or time curves from ( a ) the simulation and ( b ) the laboratory test at room temperature after Guo et al 15 , Wu et al 33 . …”
It is known that the heterogeneity caused by thermally induced micro-cracks and thermal stress can affect the mechanical behavior of granite. The laboratory-scale tests have the intrinsic limitation of non-repeatability and lack of effective methods to characterize the interaction effect between thermal micro-cracks and thermal stresses. In this study, we demonstrate how advancements in particle bonded model and moment tensor can help better understand the roles of high temperature in weakening granite and thermally induced cracking process in Brazilian test. Our results show that the types of micro-cracks (intergranular, intragranular, and transcrystalline ones) are related to their thermal expansion coefficients of mineralogical compositions. The intergranular tensile micro-cracks are predominant during the heating and heating–cooling processes. An obvious weakening of granite and non-central initiation is associated with the heterogeneity caused by the thermal damage and thermal stress. We also quantitatively evaluate the thermal damage based on orientation distribution, b-value, and nature of the sources, which gives a new microcracking perspective on tensile characteristics subjected to high temperature.
Oil and gas exploration studies have been increasingly moving deeper into the earth. The rocks in deep and ultra‐deep reservoirs are exposed to a complex environment of high temperatures and large geo‐stresses. The Tarim oilfield in the Xinjiang Uygur Autonomous Region (Xinjiang for short), China, has achieved a breakthrough in the exploration of deep hydrocarbon reservoirs at a depth of over 9000 m. The mechanical properties of deep rocks are significantly different from those of shallow rocks. In this study, triaxial compression tests were conducted on heat‐treated carbonatite rocks to explore the evolution of the mechanical properties of carbonatite rocks under high confining pressure after thermal treatment. The rocks for the tests were collected from reservoirs in the Tarim oilfield, Xinjiang, China. The experiments were performed at confining pressures ranging from atmospheric to 120 MPa and temperatures ranging from 25 to 500°C. The results show that the critical confining pressure of the brittle–ductile transition increases with increasing temperature. Young's modulus is negatively correlated with the temperature and positively correlated with the confining pressure. As the confining pressure increases, the failure mode of the specimens gradually transforms from shear fracture failure into “V”‐type failure and finally into bulging failure (multiple shear fractures). With increasing temperature, the failure angle tends to decrease. In addition, an improved version of the Mohr‒Coulomb strength criterion with a temperature‐dependent power function was proposed to describe the failure strength of carbonatite rocks after exposure to high temperature and high confining pressure. The surface of the strength envelope of this criterion is temperature dependent, which could reflect the strength evolution of rock under high confining pressures after thermal treatment. Compared with other strength criteria, this criterion is more capable of replicating physical processes.
The HF (hydraulic fracturing) technique has received widespread recognition and applications in the extraction of shale oil/gas, coalbed methane, and geothermal system.
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