Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature

Xu, Xianlei; Zhang, Z. Z.

doi:10.1155/2016/2181438

Cited by 7 publications

(5 citation statements)

References 12 publications

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“…Figure 19 shows the SEM images of fracture surfaces of granite specimens under different heating temperatures. When the temperature is lower than 800 • C, the strain energy consumed by cracking along the cleavage is the least [94], so the transgranular cleavage fracture and brittle intergranular fracture are the main fracture modes (Figure 19a-c). For such tensile brittle fractures, the critical stress of crack initiation is usually greater than or equal to the critical stress of crack propagation.…”

Section: Discussionmentioning

confidence: 99%

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

et al. 2019

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In deep geoengineering, including geothermal development, deep mining, and nuclear waste geological disposal, high temperature significantly affects the mineral properties of rocks, thereby changing their porous and mechanical characteristics. This paper experimentally studied the changes in mineral composition, pore structure, and mechanical characteristics of pyroxene granite heated to high temperature (from 25 °C to 1200 °C). The results concluded that (1) the high-temperature effect can be roughly identified as three stages: 25–500 °C, 500–800 °C, 800–1200 °C. (2) Below 500 °C, the maximum diffracted intensities of the essential minerals are comparatively stable and the porous and mechanical characteristics of granite samples change slightly, mainly due to mineral dehydration and uncoordinated thermal expansion; additionally, the failure mechanism of granite is brittle. (3) In 500–800 °C, the diffraction angles of the minerals become wider, pyroxene and quartz undergo phase transitions, and the difference in thermal expansion among minerals reaches a peak; the rock porosity increases rapidly by 1.95 times, and the newly created pores caused by high heat treatment are mainly medium ones with radii between 1 μm and 10 μm; the P-wave velocity and the elastic modulus decrease by 62.5% and 34.6%, respectively, and the peak strain increases greatly by 105.7%, indicating the failure mode changes from brittle to quasi-brittle. (4) In 800–1200 °C, illite and quartz react chemically to produce mullite and the crystal state of the minerals deteriorate dramatically; the porous and mechanical parameters of granite samples all change significantly and the P-wave, the uniaxial compressive strength (UCS), and the elastic modulus decrease by 81.30%, 81.20%, and 92.52%, while the rock porosity and the shear-slip strain increase by 4.10 times and 11.37 times, respectively; the failure mechanism of granite samples transforms from quasi-brittle to plastic, which also was confirmed with scanning electron microscopy (SEM).

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Section: Discussionmentioning

confidence: 99%

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

et al. 2019

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“…Although the constitutive model of rock damage under the coupling temperature and confining pressure is established in this paper, but more emphasis is placed on the effect of confining pressure, the temperature is only considered at 400 C. However, by the diffraction information of granite (Xu and Zhang, 2016), quartz as the main component of granite occurs reversible reaction from a quartz to b quartz at 573 C, differential thermal curve of feldspar appears an endothermic valley at 700-900 C, and the crystal lattice of mica is destroyed at 997 C, leading to escapement of hydroxyl and formation of sodium feldspar. So whether the findings at 400 C are applicable to these high temperatures needs to be further verified.…”

Section: Discussionmentioning

confidence: 99%

Thermo-mechanical coupling damage constitutive model of rock based on the Hoek–Brown strength criterion

Gao

Zhang

2017

International Journal of Damage Mechanics

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Studying the thermal damage constitutive model of rock using statistical theory can better reflect the damage evolution process and the stress–strain relationship of rock under temperature and loading, which is one of the key problems especially in deep rock mechanics. The thermal-mechanical coupling damage constitutive model of rock is established using the Hoek–Brown strength criterion, based on the Weibull distribution and the continuous damage theory. The rationality of the model is also verified by experiments. The main conclusions are as follows. The stress–strain curves of rock can be divided into four stages according to the damage evolution characteristics, including the non-damage of loading, damage stability expansion, damage intensification expansion, and damage stability expansion to saturation, and the method of determining the demarcation points of each stage is given clearly. The initial damage point of the rock is about 25% of the peak stress, the damage value is about 0.3 when the rock reaches the peak stress and about 0.6 when reaches the residual stress. Both the damage value and the strain energy release rate of the rock corresponding to the peak stress show exponential growth with the increase in confining pressure. The maximum damage evolution rate of the rock shows exponential decay as the confining pressure rises, indicating that the confining pressure can delay the development of cumulative damage. The modified damage constitutive model considering compaction coefficient is in good agreement with the test curves in the stage of compaction, linear elasticity, yield, and pre-peak strength. It is hoped that through the research of this paper, it can provide references for studying the macroscopic mechanical response from the damage propagation characteristics of the rock in the future.

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“…According to (9), the curves of rock total damage with axial strain and axial stress at various temperatures are shown in Figures 12 and 13. e initial D is the corresponding D T when strain and stress equal to zero, and then D increases with the rise of strain, which can re ect the whole rock failure process of microcracks compaction, initiation, expansion, and destruction.…”

Section: Total Damage (D)mentioning

confidence: 99%

“…e characteristics of rock strength and deformation will be affected by high temperature [1][2][3][4][5][6][7][8][9]. Many rock engineerings, such as nuclear waste disposal [10], geothermal resource development [11,12], underground engineering stability [13], postdisaster reconstruction [14,15], and other projects, are inevitably related to high temperature.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

Zhang

2018

Advances in Materials Science and Engineering

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Acoustic emission (AE) signals can be detected from rocks under the effect of temperature and loading, which can be used to reflect rock damage evolution process and predict rock fracture. In this paper, uniaxial compression tests of granite at high temperatures from 25°C to 1000°C were carried out, and AE signals were monitored simultaneously. e results indicated that AE ring count rate shows the law of "interval burst" and "relatively calm," which can be explained from the energy point of view. From 25°C to 1000°C, the rock failure mode changes from single splitting failure to multisplitting failure, and then to incomplete shear failure, ideal shear failure, and double shear failure, until complete integral failure. ermal damage (D T ) defined by the elastic modulus shows logistic increase with the rise of temperature. Mechanical damage (D M ) derived by the AE ring count rate can be divided into initial stage, stable stage, accelerated stage, and destructive stage. Total damage (D) increases with the rise of strain, which is corresponding to the stress-strain curve at various temperatures. Using AE data, we can further analyze the mechanism of deformation and fracture of rock, which helps to gather useful data for predicting rock stability at high temperatures.

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Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature

Cited by 7 publications

References 12 publications

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

Thermo-mechanical coupling damage constitutive model of rock based on the Hoek–Brown strength criterion

Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

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