Thermal deterioration of high-temperature granite after cooling shock: multiple-identification and damage mechanism

Shen, Yanjun; Hou, Xin; Yuan, Jiangqiang; Xu, Zhenhao; Hao, Jianshuai; Gu, Linjun; Zhi-yun, Liu

doi:10.1007/s10064-020-01888-7

Cited by 42 publications

(13 citation statements)

References 47 publications

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“…In short, the difference between different experiments mainly occurs in the mild temperature range (25 ℃ -300 ℃), when the temperature is is higher than this range, the above tests all obtained the conclusion that with the temperature increases, the strength of the specimen decreases, the peak strain increases, and the failure mode shows a tendency of brittleness-ductility transition. In the mild temperature range, some experiments showed that the strength of granite specimens increases with increasing temperature (Yang et al, 2017;Rossi et al, 2018); while some other experiments showed that the strength of the specimen decreases with the increase of temperature (Shen et al, 2020). The reasons for these differences are complex, including rock mineral composition, porosity, initial water content and some other factors (Wong et al, 2020).…”

Section: Numerical Simulations Of Uniaxial Compression Tests After Different Temperature Treatments and Biaxialmentioning

confidence: 99%

“…Many factors are influencing the behavior of hydraulic fracturing in EGS, including state quantities such as confining pressure and temperature, mechanical properties of rock and injected fluid, and the coupling effect of these parameters. Due to the limitations in the conditions of experimental studies, many researchers have studied the influence of a single factor on conventional rock specimens: the effects of high-temperature treatments of granite samples (Yang et al, 2017), the impact of thermal deterioration on the physical and mechanical properties of rocks after multiple cooling shocks (Shen et al, 2020), or an intragranular damage mechanism in the brittleductile transition in porous sandstone (Wang et al, 2008), for example. Although these studies have made elucidating discussion on the brittle-ductile transition under high confining pressure or the effect of hightemperature treatment, their results could provide no direct indication for the hydraulic fracturing process in EGS.…”

Section: Introductionmentioning

confidence: 99%

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Numerical simulation of hydraulic fracturing in enhanced geothermal systems considering thermal stress cracks

Zhou

Mikada

Takekawa

et al. 2021

Preprint

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With the increasing attention to clean and economical energy resources, geothermal energy and enhanced geothermal systems (EGS) have gained much importance. For the efficient development of deep geothermal reservoirs, it is crucial to understand the mechanical behavior of reservoir rock and its interaction with injected fluid under high temperature and high confining pressure environments. In the present study, we develop a novel numerical scheme based on the distinct element method (DEM) to simulate the failure behavior of rock by considering the influence of thermal stress cracks and high confining pressure for EGS. We validated the proposing method by comparing our numerical results with experimental laboratory results of uniaxial compression tests under various temperatures and biaxial compression tests under different confining pressure regarding failure patterns and stress-strain curves. We then apply the developed scheme to the hydraulic fracturing simulations under various temperatures, confining pressure, and injection fluid conditions. Our numerical results indicate that the number of hydraulic cracks is proportional to the temperature. At a high temperature and low confining pressure environment, a complex crack network with large crack width can be observed, whereas the generation of the micro cracks is suppressed in high confining pressure conditions. In addition, high-viscosity injection fluid tends to induce more hydraulic fractures. Since the fracture network in the geothermal reservoir is an essential factor for the efficient production of geothermal energy, the combination of the above factors should be considered in hydraulic fracturing treatment in EGS.

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Section: Numerical Simulations Of Uniaxial Compression Tests After Different Temperature Treatments and Biaxialmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical simulation of hydraulic fracturing in enhanced geothermal systems considering thermal stress cracks

Zhou

Mikada

Takekawa

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Gautam et al [10] conducted uniaxial tensile and microscopic tests of granite after naturally cooling from high temperatures and established the relationship between the thermal damage and the tensile strength. Shen et al [11,12] performed a cooling shock treatment on perforated granite using a calcium chloride solution. ey found that when the temperature was above 550°C, as the fluid was injected, obvious macrofractures appeared around the injection hole of the rock, and the lower the refrigerant temperature, the more pronounced the macrofractures.…”

Section: Introductionmentioning

confidence: 99%

Effects of Different Conditions of Water Cooling at High Temperature on the Tensile Strength and Split Surface Roughness Characteristics of Hot Dry Rock

Cui

Tang

Jiang

2020

Advances in Civil Engineering

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To investigate the effects of the different conditions of water cooling at high temperature on the tensile strength and split surface roughness characteristics of hot dry rock in the Songliao Basin, the physical characteristics, tensile strength, and split surface roughness of granite under different conditions of water cooling at high temperature were studied. In addition, the relationship between tensile strength and split surface roughness under different conditions of water cooling at high temperature was established. The results showed the following: (1) as the rock temperature increased, the number of water injection cycles increased or the water injection temperature decreased, the mechanical properties of the specimen weakened, and the roughness of the split surface increased. The threshold for the effect of the rock temperature on the split surface roughness of granite was 300°C. At 400°C, the tensile strength greatly decreased. At 600°C, the tensile strength, height mean square error (MSE), fluctuation difference, roughness coefficient, and roughness profile index of the specimen were 0.21, 2.51, 2.57, 8.92, and 1.06 times those at 100°C, respectively. After five heating-cooling cycles, the tensile strength, height MSE, fluctuation difference, roughness coefficient, and roughness profile index of the specimen were 0.57, 1.33, 1.49, 1.29, and 1.01 times those after one cycle, respectively. (2) The roughness angle calculated using the root mean square of the first derivative of the profile was always greater than that derived using the roughness profile index. In addition, the higher the temperature, the lower the water temperature, the more high-temperature-water cooling cycles, the greater the difference between the above two calculations. (3) When the tensile strength varies, the factors affecting the variation in the height MSE and surface roughness were in the following descending order: rock temperature, number of heating-cooling cycles, and water temperature. In addition, the higher the tensile strength, the lower the roughness coefficient. This study is expected to provide a reference for the selection of different conditions of water cooling at high temperature for thermal recovery in the Songliao Basin.

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“…e widely distributed permafrost in the Qinghai-Tibet Plateau exhibits stronger temperature sensitivity and faster temperature rise rate than other permafrost regions with the same latitude [4][5][6]. e dynamic degradation process of frozen soil has a great impact on the stability of buildings in cold regions [7][8][9][10]. In the meanwhile, it will also lead to local environmental degradation, or further affect the global climate carbon cycle and climate change [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Assessment for Thermal Conductivity of Frozen Soil Based on Nonlinear Regression and Support Vector Regression Methods

Cui

Zhang

Liu

et al. 2020

Advances in Civil Engineering

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The comprehensive understanding of the variation law of soil thermal conductivity is the prerequisite of design and construction of engineering applications in permafrost regions. Compared with the unfrozen soil, the specimen preparation and experimental procedures of frozen soil thermal conductivity testing are more complex and challengeable. In this work, considering for essentially multiphase and porous structural characteristic information reflection of unfrozen soil thermal conductivity, prediction models of frozen soil thermal conductivity using nonlinear regression and Support Vector Regression (SVR) methods have been developed. Thermal conductivity of multiple types of soil samples which are sampled from the Qinghai-Tibet Engineering Corridor (QTEC) are tested by the transient plane source (TPS) method. Correlations of thermal conductivity between unfrozen and frozen soil has been analyzed and recognized. Based on the measurement data of unfrozen soil thermal conductivity, the prediction models of frozen soil thermal conductivity for 7 typical soils in the QTEC are proposed. To further facilitate engineering applications, the prediction models of two soil categories (coarse and fine-grained soil) have also been proposed. The results demonstrate that, compared with nonideal prediction accuracy of using water content and dry density as the fitting parameter, the ternary fitting model has a higher thermal conductivity prediction accuracy for 7 types of frozen soils (more than 98% of the soil specimens’ relative error are within 20%). The SVR model can further improve the frozen soil thermal conductivity prediction accuracy and more than 98% of the soil specimens’ relative error are within 15%. For coarse and fine-grained soil categories, the above two models still have reliable prediction accuracy and determine coefficient (R2) ranges from 0.8 to 0.91, which validates the applicability for small sample soils. This study provides feasible prediction models for frozen soil thermal conductivity and guidelines of the thermal design and freeze-thaw damage prevention for engineering structures in cold regions.

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Thermal deterioration of high-temperature granite after cooling shock: multiple-identification and damage mechanism

Cited by 42 publications

References 47 publications

Numerical simulation of hydraulic fracturing in enhanced geothermal systems considering thermal stress cracks

Numerical simulation of hydraulic fracturing in enhanced geothermal systems considering thermal stress cracks

Effects of Different Conditions of Water Cooling at High Temperature on the Tensile Strength and Split Surface Roughness Characteristics of Hot Dry Rock

Assessment for Thermal Conductivity of Frozen Soil Based on Nonlinear Regression and Support Vector Regression Methods

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