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Jingwei Gao

Bio: Jingwei Gao is an academic researcher from Beijing University of Technology. The author has contributed to research in topics: Temperature cycling & Compressive strength. The author has an hindex of 4, co-authored 7 publications receiving 289 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors evaluate the thermal effects on the geophysical properties of granite and show that the dynamic strength decreases linearly as temperature increases but increases as the impact pressure increases.

212 citations

Journal ArticleDOI
TL;DR: In this article, the thermal effects on micro-properties of granite were experimentally studied and two indexes (heterogeneity coefficient and anisotropy coefficient) were proposed to describe the micro properties of granite.

171 citations

Journal ArticleDOI
TL;DR: In this paper, the spatial gradient distributions of thermal shock-induced damage to granite with respect to associated deterioration mechanisms were investigated by computed tomography (CT) and image analysis techniques, and the influence of the preheating temperature on the spatial gradients of the damage was discussed.
Abstract: In this study, we attempted to investigate the spatial gradient distributions of thermal shock-induced damage to granite with respect to associated deterioration mechanisms. First, thermal shock experiments were conducted on granite specimens by slowly preheating the specimens to high temperatures, followed by rapid cooling in tap water. Then, the spatial gradient distributions of thermal shock-induced damage were investigated by computed tomography (CT) and image analysis techniques. Finally, the influence of the preheating temperature on the spatial gradients of the damage was discussed. The results show that the thermal shock induced by rapid cooling can cause more damage to granite than that induced by slow cooling. The thermal shock induced by rapid cooling can cause spatial gradient distributions of the damage to granite. The damage near the specimen surface was at a maximum, while the damage inside the specimen was at a minimum. In addition, the preheating temperature can significantly influence the spatial gradient distributions of the thermal shock-induced damage. The spatial gradient distribution of damage increased as the preheating temperature increased and then decreased significantly over 600 °C. When the preheating temperature was sufficiently high (e.g. 800 °C), the gradient can be ignored.

92 citations

Journal ArticleDOI
Abstract: In many geotechnical engineering, such as underground disposal of nuclear waste, geothermal energy exploitation and deep mining, the rock and rock mass is subjected to thermal cycling effects. Heating and cooling cycles induce micro-defect generation and propagation in rock and rock mass, which change the properties of rock, further inducing engineering disasters (Li et al. 2019). Therefore, the study of the thermal cycling effect on rock becomes significantly important for preventing and controlling engineering disaster (Li et al. 2011; Villarraga et al. 2018; Liu et al. 2019). The thermal cycling effects on physical and mechanical properties of rocks have been extensively studied. Wang et al. (2016) carried out a series studies about thermal cycling effects on physical and mechanical behavior of the red-sandstone. A weathering model was built to predict the mechanical degradation of rock after thermal cycles. Zhu et al. (2018) studied the thermal cycling effects on compressive and tensile behavior of granite. Rong et al. (2018) investigated the thermal cycling effect on the P-wave velocity and uniaxial compression mechanical properties of two types of rocks. Researches show that both the wave velocity and mechanical strength generally decrease with an increase in number of thermal cycles, but both the porosity and permeability present an increase trend. To understand thermal cycling induced deterioration mechanisms of rocks, a series of micro-property investigations were performed (Yang et al. 2019; Jin et al. 2019). Peng et al. (2019) investigated the thermal cycling effects on density, width, length, and directivity of cracks of marble specimen by optical microscopy and established a quantitative relation between mechanical behavior and crack density. Wu et al. (2019) observed cracking pattern of rocks after thermal cycling by SEM. Researches show that the change of macrophysical and mechanical properties of rocks after thermal cycling treatments is mainly attributed to the generation and propagation of micro-defects. With an increase of the number of thermal cycles, the width and length of micro-cracks present an increase trend, which further cause the decrease of strength and the increase of permeability. The plane scanning techniques cannot provide quantitative spatial distribution characters of thermal induced microdefects. Studying the spatial distribution characters of thermal induced micro-defects facilitates our understanding the thermal induced deterioration mechanisms of rocks (Li et al. 2015; Zhang et al. 2018). The computed tomography technology (CT) is available to qualitatively observe spatial distribution of damage (Isaka et al. 2019). However, quantitatively calculate the spatial distribution of thermal induced micro-defect of rock still not fully explored. In the present study, the three-dimensional spatial distribution of micro-defects of granite induced by thermal cycles was studied by CT. The heterogeneity coefficient and anisotropy coefficient were introduced to define the micro-defects quantitatively. The effects of thermal cycles on heterogeneity coefficient and anisotropy coefficient were discussed.

21 citations

Journal ArticleDOI
TL;DR: In this paper, real-time computed tomography (CT) scanning was performed on thermally damaged granite subjected to compression loading to observe the evolution of spatial three-dimensional (3D) microcracks and planar two-dimensional micro-cracks.
Abstract: In high-temperature rock engineering projects, rocks are subjected to external loads. Studying the cracking behavior of thermally damaged rock under uniaxial loading is of great significance to engineering. In the present study, real-time computed tomography (CT) scanning was performed on thermally damaged granite subjected to compression loading to observe the evolution of spatial three-dimensional (3D) microcracks and planar two-dimensional (2D) microcracks. The porosity and crack length were further introduced to quantify microcracking behavior. The effects of the load on the 3D microcrack volume distribution and the length of 2D microcracks with different orientations were discussed. The results show that real-time CT imaging intuitively presents the evolutionary process of realistic microcrack morphology during loading. As the load level increases, the porosity of the specimen and the total length of 2D microcracks experience stages of slow decrease, slow increase, and rapid increase. The proportion of microcracks with larger volumes decreases and then increases as the load level increases. In the slice parallel to the loading direction, the length of microcracks within an angle range of 30°–90° to the loading direction decreases as the load level increases. In the slice perpendicular to the loading direction, the microcrack length distribution exhibits obvious anisotropy as the load level increases.

12 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, an optimal basalt fiber content was determined basing firstly on suitable printability and then on mechanical performance using a self-developed 3D printer for extrusion of the cementitious material and also for mechanical enhancement of fiber alignment along the print direction.

224 citations

Journal ArticleDOI
TL;DR: In this article, the thermal effects on micro-properties of granite were experimentally studied and two indexes (heterogeneity coefficient and anisotropy coefficient) were proposed to describe the micro properties of granite.

171 citations

Journal ArticleDOI
TL;DR: In this article, the results from tests performed to investigate the tensile mechanical characteristics of granite after exposure to heating and cooling treatments were analyzed using the Brazilian disc method, and the results showed that the water-cooled samples exhibited the largest decrease in P-wave velocity and the largest numbers of newly generated cracks on the surface, which indicates that the samples heated and cooled at higher cooling rates were more susceptible to the heating/cooling treatments.

124 citations

Journal ArticleDOI
TL;DR: In this article, a comparison study on brittle and ductile laboratory rock-like specimens that contain nine pre-existing flaws subjected to uniaxial compression is conducted, and the fractal dimension estimation method is introduced to quantitatively track the fracture process.

106 citations

Journal ArticleDOI
TL;DR: Since the NMM adopts an implicit scheme to solve the problem, a large time step is allowed, which makes it possible to realistically model the static loading condition without need of raising up the loading rate required by other explicit-based methods.
Abstract: In this study, a zero-thickness cohesive element-based Numerical Manifold Method (NMM) combined with detailed micro-scale characterization is proposed for modeling the rock mechanical response and failure process of rock To represent the rock micro-structure, a Voronoi tessellation technique is adopted to generate the random polygonal grains Since the contact fracture model not only requires input micro-parameters which are difficult to be obtained directly from laboratory tests, but also becomes very time consuming due to extensive contact searching and judging processes, a zero-thickness cohesive element is inserted between the rock grains to more efficiently and accurately capture the interaction between the rock grains before failure To more efficiently model the interaction between the rock grains after failure, the original contact searching technique is improved To validate and illustrate the efficiency of the developed method, a series of numerical tests are performed using the developed method and their results are compared with those obtained from laboratory tests and original NMM predictions Since the NMM adopts an implicit scheme to solve the problem, a large time step is allowed, which makes it possible to realistically model the static loading condition without need of raising up the loading rate required by other explicit-based methods

96 citations