scholarly journals Desorption and Transport of Temperature-Pressure Effect on Adsorbed Gas in Coal Samples from Zhangxiaolou Mine, China

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Xiaohu Zhang ◽  
Wenxin Li ◽  
Gan Li
Keyword(s):  
Uniaxial Compression ◽  
Negative Pressure ◽  
Coal Sample ◽  
Coupling Effect ◽  
Test System ◽  
Effect Of Temperature ◽  
Compression Process ◽  
Sem Images ◽  
Adsorbed Gas ◽  
Roadway Stability

Abstract The development of coal seam fissures and gas migration process caused by mining disturbance has an extremely important influence on gas control and roadway stability. In this study, the desorption, diffusion, and migration tests of adsorbed gas under the coupling effect of temperature and uniaxial compression were conducted on four coal samples from Zhangxiaolou mine, using the temperature and pressure coupling test system of deep coal rocks. The test confirms that the higher the temperature, the faster the desorption and emission of the adsorbed gases in the coal, and the larger the volume of the emitted gases. Meanwhile, it is found that the adsorbed gases in the coal samples of Zhangxiaolou mine are carbon dioxide and methane in the order of content. It is found that during the uniaxial compression process, several large negative values of the pressure of the emitted gas occur during the stable growth stage of the crack. This indicates that the crack expansion makes a new negative pressure space inside the coal sample, and the negative pressure values increase continuously during the unstable growth phase of the crack until the coal sample is destroyed. And after the axial pressure is removed, the escaped gas pressure shows a large positive value due to the rebound of the coal matrix and the continuous desorption of a large amount of adsorbed gas from the new crack location, which has a significant hysteresis with respect to the occurrence of the peak stress. Meanwhile, the SEM images of the coal samples before and after the test are analyzed to confirm the cause of the negative pressure generation.

scholarly journals Acoustic Emission Response Characteristics of Anthracitic Coal under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Haiyan Wang ◽  
Gongda Wang ◽  
Guojun Zhang ◽  
Feng Du ◽  
Ji Ma
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of the AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation, and fracture evolution of microcracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of the coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of the coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of the coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there is some nonuniformity and anisotropy in raw coal samples. The ring counts, energy counts, and AE events with time in uniaxial compression process have approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring counts and energy counts, the AE events have a good positioning function, which can better reflect the evolution of internal cracks of coal samples during uniaxial compression.

scholarly journals Acoustic emission response characteristics of anthracitic coal under uniaxial compression

2020 ◽  
Author(s):  
Feng Du ◽  
Kai Wang ◽  
Guojun Zhang ◽  
Gongda Wang ◽  
Qian Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Coal Sample ◽  
Compression Process ◽  
Deformation And Failure ◽  
Response Characteristics ◽  
Fracture Evolution ◽  
Anthracite Coal ◽  
Coal Deformation

Abstract The damage evolution of coal is accompanied by the generation of acoustic emission (AE) signal. Through the analysis and research of AE response characteristics of coal deformation and failure, it is helpful to reveal the initiation, propagation and fracture evolution of micro cracks in coal. In this work, taking the anthracite coal as research object, the basic mechanical parameters of coal samples were obtained by ultrasonic tests and uniaxial compression experiments. Meanwhile, the AE response characteristics of coal samples during uniaxial compression were obtained through AE experiments. The results show that when the density is low, the wave velocity of coal sample decreases with the increase of density. When the density is higher than a certain value, the wave velocity of coal sample increases with the increase of density. Through the measurement of ultrasonic wave velocity, it is found that there are some non-uniformity and anisotropy in raw coal samples. The distribution of ring count, energy count and AE events with time in uniaxial compression process is approximately normal distribution. The AE events are concentrated in the elastic stage and yield stage, and the energy amplitude of AE events is higher in the plastic stage. Compared with the ring count and energy count, the AE events have good positioning function, which can better reflect the evolution of internal cracks in coal samples during uniaxial compression.

Research of Coal Pores and Integrity Evaluation Method Based on Fractal Theory

2014 ◽  
Vol 670-671 ◽  
pp. 258-262 ◽  
Author(s):  
Ji Li ◽  
Xin Wu
Keyword(s):  
Fractal Dimension ◽  
Coal Sample ◽  
Evaluation Method ◽  
Structural Integrity ◽  
Gas Adsorption ◽  
Fractal Theory ◽  
Physical And Mechanical Properties ◽  
Box Dimension ◽  
Sem Images ◽  
Sem Image

Coal is a natural porous media, its porosity and structural integrity influenced the gas adsorption and desorption characteristics greatly, as well as physical and mechanical properties of coal. Scanning electron microscopy (SEM) is applied to acquire SEM image of four kinds of coal samples at different zoom levels, and the box dimension can be worked out based on the pore preprocessing of SEM images. Then, the numerical value of box dimension is used to describe the development degree of the four kinds of coal sample and four development degrees’ sequence. At last, the intrinsic relevance between fractal dimension and other parameters is analyzed through mathematic method. The results show as follows: coal sample has self-similarity characteristic; the fractal dimension is related to both the total number of pores and porosity degree; the data of the coal pore, analyzed through fractal dimension, are consistent with that through traditional method; what’s more, fractal dimension has more advantages in describing accuracy and simplicity.

The Interaction of Temperature and Bending Load on Structural Performance of Chinese Larch Wood

2012 ◽  
Vol 531-532 ◽  
pp. 122-126
Author(s):  
Hai Bin Zhou ◽  
Chuan Shuang Hu ◽  
Jian Hui Zhou
Keyword(s):  
Elevated Temperatures ◽  
Coupling Effect ◽  
Structural Performance ◽  
Effect Of Temperature ◽  
Short Exposure ◽  
Short Exposure Time ◽  
Larch Wood ◽  
Timber Construction ◽  
Bending Load ◽  
Stress Levels

Wood is being used extensively in timber construction in China. In fire-resistant design for timber construction, the main goal is to ensure that enough structural integrity is maintained during a fire to prevent structure collapse. It is important to understand its structural performance when exposed to elevated temperatures and loaded by stress levels. To study the interaction effect of Chinese larch wood, a total of 72 small clear wood samples were observed under constant stress levels when the wood temperature was elevated. The results indicated that Chinese larch wood was more susceptible to the coupling effect of temperature and stress. The interaction promoted a temporary stable flexural structure to collapse during a short exposure time.

Study on the Main Characteristics of Reflective Cracking in the Asphalt Overlay on an Old Cement Pavement

2020 ◽  
Vol 980 ◽  
pp. 244-253
Author(s):  
Chun Fu Zhu ◽  
Pei Feng Cheng ◽  
Guang Yu Zhao
Keyword(s):  
Working Conditions ◽  
Coupling Effect ◽  
Shear Crack ◽  
Effect Of Temperature ◽  
Reflective Cracking ◽  
Effective Prevention ◽  
Finite Element Software ◽  
Asphalt Overlay ◽  
Prevention And Treatment ◽  
Reflection Crack

The purpose of this study is to explore the forms and characteristics of reflection crack in asphalt overlay of old cement pavement, so as to provide reference for effective prevention and treatment of reflection crack.By means of ANSYS finite element software, considering the coupling effect of temperature and vehicle in different working conditions, the influence of cooling on asphalt overlay was analyzed, and the location and form of crack were discussed.The analysis results show that tensile crack and shear crack are more likely to occur near the joint of old cement pavement, and shear crack is more likely to occur in areas outside the joint, about 1/2 wheel length from the joint of cement pavement.The prevention and treatment of crack at different locations should be carried out according to different working conditions.

Effect of Temperature on the Material Properties and the Results of Thermal Stress Analysis

2017 ◽  
Vol 729 ◽  
pp. 8-12
Author(s):  
Tae Kyung Kim ◽  
Dong Kwon Oh ◽  
Kwang Ju Lee
Keyword(s):  
Thermal Stress ◽  
Elastic Modulus ◽  
Stress Analysis ◽  
Material Properties ◽  
Room Temperature ◽  
Test System ◽  
Effect Of Temperature ◽  
Air Conditioning System ◽  
Thermal Stress Analysis ◽  
Different Levels

Use of correct values of material properties is important in structural analysis. When incorrect values are used in the analysis, engineers may end up with misleading conclusions. The magnitudes of elastic modulus and strength are usually measured from experiments at room temperature. When these values are used in the thermal stress analysis of structures, the results may not be reliable because the magnitudes of elastic modulus and strength depend on temperature. The temperature distribution of HVAC (Heating, Ventilation and Air Conditioning) system was analyzed. The material properties were measured using MTS810 material test system and MTS 651 environmental chamber at different levels of temperature. They were used in the thermal stress analysis of HVAC system. It was found that the results of thermal stress analysis were significantly different from the results using material properties which were measured from experiments at room temperature.

Study on Microstructure Differences of Coal Samples before and after Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jiajia Liu ◽  
Yingxiang Fang ◽  
Gaini Jia ◽  
Shouqi Chen ◽  
Jianmin Hu
Keyword(s):  
Electron Microscopy ◽  
Coal Seam ◽  
Coal Sample ◽  
Coal Seam Gas ◽  
Adsorbed Gas ◽  
Transmission Electron ◽  
Parallel Layer ◽  
Before And After ◽  
Spectrum Area ◽  
Nmr Techniques

The microscopic pore structure of coal affects the content of adsorbed gas. The microstructure of coal sample before and after loading is different, which will affect the adsorption and permeability of coal seam gas. In order to study this difference, the authors carried out mercury intrusion experiments on coal containing different coal samples and used nondestructive nuclear magnetic resonance (NMR) techniques, scanning electron microscopy, and transmission electron microscopy, to study the microstructure of coal samples before and after loading. The experimental results show that the pores of coal samples are mainly micropores and small pores, and the mesopores and macropores are relatively few. The T2 spectrum area of the coal sample is significantly increased after loading, and the parallel-layer coal samples’ T2 spectrum area is 46735, which is 9112 more than the vertical layer coal samples. The T2 spectrum of the vertical coalbed of saturated water samples shows a three-peak shape, the peak of the T2 spectrum is 12692, and the parallel bedding shows a bimodal morphology. The peak area of the T2 spectrum is 11277. The permeability of the parallel bedding coal sample is good, and the coal sample exhibits anisotropic properties. The pores and cracks of the coal samples increased after loading, and the localized area of the coal sample collapsed and formed a fracture zone, which was not conducive to the occurrence of coal seam gas. Further explanation of the changes in the permeability of the coal sample before and after loading will affect the gas storage and transportation.

scholarly journals Numerical and experimental studies on a novel magneto-rheological fluid brake based on fluid–solid coupling

2019 ◽  
Vol 103 (1) ◽  
pp. 003685041987900 ◽  
Author(s):  
Shujun Li ◽  
Wenjun Meng ◽  
Yao Wang
Keyword(s):  
Heat Dissipation ◽  
Coupling Effect ◽  
Experimental Studies ◽  
Test System ◽  
Structure Design ◽  
Brake Disc ◽  
Braking Torque ◽  
Braking Process ◽  
Magneto Rheological ◽  
The Impact

The previous work of the authors indicated that the fluid–solid coupling effect of the magneto-rheological fluid and the brake disc is a necessary focus during braking process. In this study, a novel design of magneto-rheological fluid brake was proposed and studied theoretically and numerically, aiming to solve the prominent problem of heat dissipation, especially in the case of single emergency braking. First, based on the modified Bingham model, a parameter defined as the apparent equivalent viscosity was utilized to represent the relationship of magnetic field, flow field, and temperature field. The braking torque and the formula for calculating the impact factor of fluid–solid coupling employed for characterizing the associations among the thermal field and the stress field were established based on fluid–solid coupling. With a detailed explanation of simulation method, the distribution disciplinarian’s numerical simulation of each field was analyzed using COMSOL software. To validate the accuracy of the established model on the designed magneto-rheological fluid brake, the prototype was also manufactured, and results achieved experimentally which were measured on inertia test system of brake, for braking torque, motion parameters, and surface temperature in braking process, were compared with simulations. Simulation results manifested that the designed magneto-rheological fluid brake’s magnetic circuit structure is feasible based on magnetic induction intensity distribution. Finally, it has been shown that the simulations appear to be basically consistent with the experimental results, and the heat dissipation of the designed magneto-rheological fluid brake is partially improved. These results might contribute to the structure design, optimization, and improvement of magneto-rheological fluid products, extending the previous work on fluid–solid coupling analyses.

Particle Flow Simulation of Rock Uniaxial Compression Process

2011 ◽  
Vol 90-93 ◽  
pp. 497-500
Author(s):  
Yan Chun Yin ◽  
Tong Bin Zhao ◽  
Yun Liang Tan ◽  
Chuan Wei Zang
Keyword(s):  
Uniaxial Compression ◽  
Flow Simulation ◽  
Uniaxial Compression Test ◽  
Compression Process ◽  
Deformation Localization ◽  
Indirect Tension ◽  
Engineering Significance ◽  
Scientific Significance ◽  
Softening Stage ◽  
Particle Flow Simulation

The research of rock deformation and breaking has important scientific significance and engineering significance. Deformation is a long process, while the breaking happens in a monent relatively. In this paper the rock uniaxial compression test was simulated by using PFC2D. The complete curve of stress-strain was devided into six stages: compaction stage, elastic deformation stage, plastic sclerosis stage, plastic softening stage, breaking stage and breaking residual stage. It was found that the deformation localization generated the formation and extension of the cracks. When there were enough cracks, the specimen began to damage. Only a few crack bands evolved to breaking bands. The specimen’s breaking was mainly caused by indirect tension, supplemented by shear.

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