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Yunpei Liang
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

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Journal article
Published: 23 October 2020 in Process Safety and Environmental Protection
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The coal’s permeability plays a crucial role in coalbed methane (CBM) extraction and coal seam CO2 sequestration. An accurate understanding of permeability rebound and recovery is therefore essential. This study establishes an improved fully coupled gas migration model for CBM extraction. The permeability rebound and recovery times as well as rebound values are proposed to accurately quantify permeability evolution during CBM extraction. The evolution of these three parameters under the influence of different factors are evaluated in detail, such as initial gas pressure, the diffusion coefficient, and the permeability. The results show that the permeability rebound and recovery times increase along with initial gas pressure and the amount over time rises rapidly under high gas pressures. As the initial gas pressure increases, the permeability rebound value decreases. However, initial diffusion coefficient and permeability have a negative trend in permeability rebound, recovery time, and rebound value. These tendencies are particularly large for low initial permeabilities and diffusion coefficients, yet the change in rebound time is smaller than the one in recovery time. Finally, inspired by the relationship between permeability rebound and gas pressure change during CBM extraction, the evolution of coal seam permeability under different CO2 injection method is discussed. A stepwise increasing-pressure CO2 injection method is also proposed, which could effectively increase the volume of CO2 sequestered and reduce project costs. Therefore, our findings shall shed light on improving coal mine safety production and reducing greenhouse gas emission.

ACS Style

Erlei Su; Yunpei Liang; Quanle Zou; Minghan Xu; Agus P. Sasmito. Numerical analysis of permeability rebound and recovery during coalbed methane extraction: Implications for CO2 injection methods. Process Safety and Environmental Protection 2020, 149, 93 -104.

AMA Style

Erlei Su, Yunpei Liang, Quanle Zou, Minghan Xu, Agus P. Sasmito. Numerical analysis of permeability rebound and recovery during coalbed methane extraction: Implications for CO2 injection methods. Process Safety and Environmental Protection. 2020; 149 ():93-104.

Chicago/Turabian Style

Erlei Su; Yunpei Liang; Quanle Zou; Minghan Xu; Agus P. Sasmito. 2020. "Numerical analysis of permeability rebound and recovery during coalbed methane extraction: Implications for CO2 injection methods." Process Safety and Environmental Protection 149, no. : 93-104.

Journal article
Published: 10 October 2020 in Fuel
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Injecting CO2 in deep coal seams for enhanced coalbed methane recovery (ECBM) also benefits the environment through simultaneous CO2. Most studies have concentrated on the changes of pore structures that result from sustained supercritical CO2 (ScCO2) treatment. Conversely, the effects of cyclic ScCO2 treatment have been rarely investigated. In this study, a high-pressure reactor system was used to perform cyclic ScCO2 treatment of long-flame coal. Nuclear magnetic resonance techniques and low-pressure nitrogen gas adsorption were employed to determine the fractal dimensions of coal samples and quantitatively characterize their pore structures before and after cyclic treatment. The results demonstrated that the porosity and proportion of macropores increased significantly after treatment. Therefore, new pores were formed, and some small pores might have been converted into macropores. As the treatment duration increased, the daily average porosity rate exhibited an increasing trend that was presumably caused by the effects of coal matrix fatigue. Further, a decreasing tendency was captured in both the pore-surface fractal dimensions of adsorption pores and the pore-volume fractal dimensions of seepage pores, while increasing the cyclic treatment. This phenomenon after treatment indicated that pore roughness and complexity were decreased. A conceptual model was proposed to explain the mechanisms underlying the evolution of coal-pore structures during the treatments, and the effects of the cyclic injection on the CO2-ECBM field were also analyzed. Therefore, our findings have important guiding significance for selecting suitable CO2 injection methods for CO2-ECBM projects.

ACS Style

Erlei Su; Yunpei Liang; Quanle Zou. Structures and fractal characteristics of pores in long-flame coal after cyclical supercritical CO2 treatment. Fuel 2020, 286, 119305 .

AMA Style

Erlei Su, Yunpei Liang, Quanle Zou. Structures and fractal characteristics of pores in long-flame coal after cyclical supercritical CO2 treatment. Fuel. 2020; 286 ():119305.

Chicago/Turabian Style

Erlei Su; Yunpei Liang; Quanle Zou. 2020. "Structures and fractal characteristics of pores in long-flame coal after cyclical supercritical CO2 treatment." Fuel 286, no. : 119305.

Journal article
Published: 12 June 2020 in Journal of CO2 Utilization
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The geological sequestration of CO2 in unmineable coal seams has gradually become one of the most effective means of responding to the global greenhouse effect. Presently, the cyclic injection of CO2 into coal seams is utilized in some enhanced CBM recovery projects with CO2 sequestration; therefore, a proper understanding of the effects of the cyclic saturation of supercritical CO2 (ScCO2) on coal is essential. Here, we present a series of uniaxial compressive strength (UCS) tests on bituminous coal subjected to both sustained and cyclic ScCO2 saturation. Nuclear magnetic resonance and acoustic emission (AE) are used to investigate changes in the pore structure distribution and porosity, as well as the fracture propagation. The results indicate that ScCO2 saturation enhances the continuity of the pore volume distribution, while cyclic saturation has a stronger influence on the pore structure. Furthermore, samples subjected to cyclic saturation exhibit significantly greater decreases in UCS and elastic modulus than the sustained-saturation samples, owing to mechanical fatigue caused by the cyclic saturation. The AE results show that cyclic saturation produces multiple signal releases in the form of unstable crack propagation, reducing crack closure and enhancing stable crack propagation. We also analyze the failure mechanism of coal samples under cyclic ScCO2 saturation in terms of the pore structure and mechanical changes experienced and discuss the influence of the cyclic injection of CO2 into coal seams. Hence, the results of this study are expected to provide a reference for the selection of appropriate CO2 injection methods and safety assessments for field projects involving coal-seam CO2 sequestration.

ACS Style

Erlei Su; Yunpei Liang; Xianyin Chang; Quanle Zou; Minghan Xu; Agus P. Sasmito. Effects of cyclic saturation of supercritical CO2 on the pore structures and mechanical properties of bituminous coal: An experimental study. Journal of CO2 Utilization 2020, 40, 101208 .

AMA Style

Erlei Su, Yunpei Liang, Xianyin Chang, Quanle Zou, Minghan Xu, Agus P. Sasmito. Effects of cyclic saturation of supercritical CO2 on the pore structures and mechanical properties of bituminous coal: An experimental study. Journal of CO2 Utilization. 2020; 40 ():101208.

Chicago/Turabian Style

Erlei Su; Yunpei Liang; Xianyin Chang; Quanle Zou; Minghan Xu; Agus P. Sasmito. 2020. "Effects of cyclic saturation of supercritical CO2 on the pore structures and mechanical properties of bituminous coal: An experimental study." Journal of CO2 Utilization 40, no. : 101208.

Original paper
Published: 07 December 2019 in Natural Resources Research
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Coalbed methane (CBM) production in the overlying strata of coal reservoirs is often hampered by the unknown distribution of the mining-induced fractures. Mining-induced fractures are CBM migration pathways in the fractured overlying strata, and the excavation of coal seams within a mine causes the CBM in adjacent coal seams to flow into the overlying strata. The mining-induced fracture field in the overlying strata is the best place from which this CBM is drained. Here, to better understand the distributions of vertical and horizontal fractures caused by excavation, we propose a novel approach to quantify the dimensions of vertical and horizontal fractures in fractured zones. In addition, we demonstrate that there are negligible changes in the dimensions of horizontal fractures and great changes in the dimensions of vertical fractures when there is an increase in the height of the fractured zone. We further demonstrate that mining-induced angles mainly concentrate on 0°–10°, 50°–70°, 110°–120° and 170°–180°, and larger width fractures exist in both sides and top due to the de-stressed effect and fractures in the middle of model close under mining-induced stress. The approach described here could be used to improve the accuracy of cross-measure borehole positioning and the efficiency of CBM drainage.

ACS Style

Bichuan Zhang; Haitao Sun; Yunpei Liang; KeQuan Wang; Quanle Zou. Characterization and Quantification of Mining-Induced Fractures in Overlying Strata: Implications for Coalbed Methane Drainage. Natural Resources Research 2019, 29, 2467 -2480.

AMA Style

Bichuan Zhang, Haitao Sun, Yunpei Liang, KeQuan Wang, Quanle Zou. Characterization and Quantification of Mining-Induced Fractures in Overlying Strata: Implications for Coalbed Methane Drainage. Natural Resources Research. 2019; 29 (4):2467-2480.

Chicago/Turabian Style

Bichuan Zhang; Haitao Sun; Yunpei Liang; KeQuan Wang; Quanle Zou. 2019. "Characterization and Quantification of Mining-Induced Fractures in Overlying Strata: Implications for Coalbed Methane Drainage." Natural Resources Research 29, no. 4: 2467-2480.

Original paper
Published: 10 July 2019 in Natural Resources Research
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Cyclic loading widely exists in coal mining activities, and it can significantly change the mechanical and seepage characteristics of coal. In this study, raw gas-bearing coal with different coal rank was mechanically tested under three stress paths: cyclic loading with stepwise increased peak stress (path 1), with step-by-step increased peak stress (path 2) and with crossed peak stress (path 3) using a tri-axial seepage testing machine. The acoustic emission (AE) signals under different loading and unloading paths indicate different mechanical properties of the coal sample. The Kaiser point is not a good indicator of the stress history of coal. The ratios of the quiet effect of the three coal samples under the three stress paths show that loading path 1 can increase defects such as micro-cracks in the coal samples (the AE quiet period decreases), while the other two paths decrease the number of defects (the AE quiet period increases). The cumulative dissipated energy of the coal shows an exponential growth with axial effective stress. The damping coefficient of coal first decreases then increases under cyclic loading. The damage variables can be used to predict the failure of coal samples, regardless of the stress path. Our results provide theoretical support and insight into the permeability increase mechanism and strengthened permeability increase mechanism of coal seams based on cyclic-loading-induced fracturing (repetitive hydraulic fracturing) under multiple protections and gas drainage engineering.

ACS Style

Qingmiao Li; Yunpei Liang; Quanle Zou; Quangui Li. Acoustic Emission and Energy Dissipation Characteristics of Gas-Bearing Coal Samples Under Different Cyclic Loading Paths. Natural Resources Research 2019, 29, 1397 -1412.

AMA Style

Qingmiao Li, Yunpei Liang, Quanle Zou, Quangui Li. Acoustic Emission and Energy Dissipation Characteristics of Gas-Bearing Coal Samples Under Different Cyclic Loading Paths. Natural Resources Research. 2019; 29 (2):1397-1412.

Chicago/Turabian Style

Qingmiao Li; Yunpei Liang; Quanle Zou; Quangui Li. 2019. "Acoustic Emission and Energy Dissipation Characteristics of Gas-Bearing Coal Samples Under Different Cyclic Loading Paths." Natural Resources Research 29, no. 2: 1397-1412.

Research article
Published: 27 May 2019 in Energy Science & Engineering
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Coal seams in China are mainly characterizsed by low permeability and high risk of coal and gas outburst. Therefore, the elimination of coal and gas outburst risk of low‐permeability coal seam remains a hard challenge. Taking Shihuatian Coal Mine in Guizhou Province, China as an example, boreholes were slotted using high‐pressure water jet to relieve the gas pressure inside the coal seam and increase the permeability of coal mass, which thus improves the gas drainage efficiency and eliminate the outburst risk. The results show that the gas drainage efficiency of the slotted boreholes significantly increases. Compared with the conventional boreholes, the average gas concentration and flow velocity improved by 1.6 and 7.5 times, respectively. Moreover, the prediction index of outburst risk is less than the critical value after high‐pressure water jet slotting, which indicate that the coal and gas outburst risk has been effectively eliminated. The measured values of gas desorption index of drilling cuttings are all lower than the critical value after the application of the high‐pressure water jet slotting technology. The research achievements could provide a practical reference for the effective gas disaster prevention and control in low‐permeability coal seams.

ACS Style

Xie Jun; Liang Yunpei; Zou Quanle; Li Lei; Li Xuelong. Elimination of coal and gas outburst risk of low‐permeability coal seam using high‐pressure water jet slotting technology: A case study in Shihuatian Coal Mine in Guizhou Province, China. Energy Science & Engineering 2019, 7, 1394 -1404.

AMA Style

Xie Jun, Liang Yunpei, Zou Quanle, Li Lei, Li Xuelong. Elimination of coal and gas outburst risk of low‐permeability coal seam using high‐pressure water jet slotting technology: A case study in Shihuatian Coal Mine in Guizhou Province, China. Energy Science & Engineering. 2019; 7 (4):1394-1404.

Chicago/Turabian Style

Xie Jun; Liang Yunpei; Zou Quanle; Li Lei; Li Xuelong. 2019. "Elimination of coal and gas outburst risk of low‐permeability coal seam using high‐pressure water jet slotting technology: A case study in Shihuatian Coal Mine in Guizhou Province, China." Energy Science & Engineering 7, no. 4: 1394-1404.

Journal article
Published: 28 April 2019 in International Journal of Rock Mechanics and Mining Sciences
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During coal mining, the compaction of goaf and the evolution of the permeability of coal masses in goaf are of significance to the safe, high-efficiency mining operation of coal mines, and directly influence surface subsidence, air leakage, spontaneous combustion of coal, etc. Although the stress and permeability of coal masses in goaf are important, it is hard to measure the two parameters directly. Therefore, seepage testing of 7 samples of broken coal masses after being compacted under isotropic loading was carried out by using a system for the seepage test of damaged coal and rock masses to evaluate indirectly the compaction and seepage characteristics of broken coal masses in goaf. Moreover, the energy evolution of broken coal masses after compaction was analysed. The research results are summarised as follows. Under the same stress, the strain in coal samples with a single particle size was lower than that in coal samples with mixed particle sizes. For coal samples with a single particle size, the smaller the particle size was, the lower the crushing amount of particles after testing. By contrast, for coal samples with mixed particle sizes, the smaller the particle size was, the greater the crushing of particles after the test. In compressive deformation stage, the stress sensitivity of the permeability of broken coal mass decreased with the increase of the elastic modulus, decreased with the increase of effective stress, decreased with the increase of Poisson's ratio, decreased with the decrease of particle radius. During isotropic compression testing, the proportions of stored elastic energy in the total energy of coal samples with single particle sizes were larger than those of coal samples with mixed particle sizes; however, the proportion of dissipated energy in the total energy of the former was lower than that of the latter.

ACS Style

Bo Li; Yunpei Liang; Lei Zhang; Quanle Zou. Experimental investigation on compaction characteristics and permeability evolution of broken coal. International Journal of Rock Mechanics and Mining Sciences 2019, 118, 63 -76.

AMA Style

Bo Li, Yunpei Liang, Lei Zhang, Quanle Zou. Experimental investigation on compaction characteristics and permeability evolution of broken coal. International Journal of Rock Mechanics and Mining Sciences. 2019; 118 ():63-76.

Chicago/Turabian Style

Bo Li; Yunpei Liang; Lei Zhang; Quanle Zou. 2019. "Experimental investigation on compaction characteristics and permeability evolution of broken coal." International Journal of Rock Mechanics and Mining Sciences 118, no. : 63-76.

Research article
Published: 18 April 2019 in Shock and Vibration
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With mining technology and mechanization degree being improving, fully mechanized caving mining technology (FCM) has become a main method for thick coal seam extraction in China. However, roof-coal caving characteristics in turn restrict its recovery efficiency, especially for the coal seam with complicated structure (CCS), that is, the coal seam comprises hard or soft coal and gangue. In order to explore the key factors influencing the roof-coal caving and recovery characteristics, related research work has been conducted as follows: firstly, a mechanical model of CCS has been established, which indicates the strength of the coal and gangue will directly affect the roof-coal recovery. Meanwhile, based on the geological settings of Qinyuan coal mine, numerical simulation on roof-coal caving law under different thicknesses of hard or soft coal and gangue has been performed using UDEC software. The results show that the maximum principal stress will increase with the increase of mining depth, making the roof-coal to break easily. Furthermore, the range of the plastic zone of the top coal and the damage degree of the top coal increase with the increase of mining depth. Physical modeling results show that when an extraction-caving ratio is 1, the number of times the coal arch forms is 0.43 at every caving, up to a maximum of 3; the number of times coal arch forms with an extraction-caving ratio of 2 is 4.65 times larger than that with an extraction-caving ratio of 1. The probability of coal arch formation with an extraction-caving ratio of 3 is minimal, about 0.4, which is due to that the arch span is large and the curvature is small, so it is difficult to form a stable arch structure. According to the mechanical characteristics of roof-coal in Qinyuan coal mine, deep-hole blasting technique has been used to reduce the fragments of roof-coal crushed. The results show that this technique can effectively improve the recovery of roof-coal.

ACS Style

Yunpei Liang; Lei Li; Xuelong Li; KeQuan Wang; Jinhua Chen; Zhongguang Sun; Xuelin Yang. Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining. Shock and Vibration 2019, 2019, 1 -20.

AMA Style

Yunpei Liang, Lei Li, Xuelong Li, KeQuan Wang, Jinhua Chen, Zhongguang Sun, Xuelin Yang. Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining. Shock and Vibration. 2019; 2019 ():1-20.

Chicago/Turabian Style

Yunpei Liang; Lei Li; Xuelong Li; KeQuan Wang; Jinhua Chen; Zhongguang Sun; Xuelin Yang. 2019. "Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining." Shock and Vibration 2019, no. : 1-20.

Research article
Published: 27 March 2019 in Energy Science & Engineering
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Based on the Langmuir adsorption model, the adsorption constants of eighteen coal samples from the same coal mine with outburst risk, weak outburst risk, and non‐outburst risk were tested by high‐pressure capacity method under different temperature conditions. The results show that the adsorption constants a and b monotonically decrease with the increase in temperature. The relationship between a and temperature shows three stages: accelerated decreasing stage, decelerated decreasing stage, and stable stage. The b decreases with the increase in temperature also shows three stages, namely relative stability, slow decrease, and accelerated decrease. The a × b for the outburst coal seam decreases with increasing temperature, which is similar to b. The a × b for the weak and non‐outburst coal seams decreases with increasing temperature, which is similar to a. Furthermore, the a of the outburst coal seam decreases with the increase in temperature, and the decrease of b is the largest. The a of the weak and non‐outburst coal seams decreases with the increase in temperature, and the magnitude is relatively large. The b decreases slightly, with a smaller magnitude. The a × b of weak outburst seam is smaller than that of non‐outburst seam and is larger than that of outburst seam. The achievements can provide guiding significance for coal and gas outburst prevention and control.

ACS Style

Fakai Wang; Yunpei Liang; Quanle Zou. Correlation between coal and gas outburst risk and adsorption properties of coal seams. Energy Science & Engineering 2019, 7, 974 -985.

AMA Style

Fakai Wang, Yunpei Liang, Quanle Zou. Correlation between coal and gas outburst risk and adsorption properties of coal seams. Energy Science & Engineering. 2019; 7 (3):974-985.

Chicago/Turabian Style

Fakai Wang; Yunpei Liang; Quanle Zou. 2019. "Correlation between coal and gas outburst risk and adsorption properties of coal seams." Energy Science & Engineering 7, no. 3: 974-985.

Research article
Published: 25 March 2019 in Energy Science & Engineering
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Broken coal and rock masses are the major part of the goaf. The compaction characteristics of coal and rock masses and the breakage law of whose particles during compaction exert an important influence on various aspects including control of strata motion, prediction of surface subsidence, and backfill mining. In this paper, the triaxial compaction experiment on broken coal‐rock masses with different mixing ratios was carried out. The test results showed that with the increase of stresses, the strain of coal‐rock masses gradually rose while the porosity, bulking factor, and degree of compaction gradually declined. During the compaction of coal‐rock masses, the fitting curves of the strain, porosity, bulking factor, and degree of compaction with stresses of coal samples all appeared as a cubic function of stresses. The breakage behavior of coal particles underwent three stages: structure re‐arrangement and breakage of particles, particle breakage, and compression‐induced deformation of particles. With increasing stress, the crushing amount of particles gradually grew while the increase rate of the crushed particles gradually decreased and the larger the particle strength was, the lower the increase rate of the crushing amount. Additionally, in the compaction process of samples, particle breakage mainly appeared before the stress reached to 8 MPa while the coal and rock particles were hardly crushed after the stress was larger than 8 MPa. With increasing stresses, the particle size gradation of samples gradually became reasonable and the lower the particle strength of samples was, the more reasonable the particle size gradation of compacted samples. The particle size gradation of various compacted and crushed samples showed a favorable fractal characteristic. In the stage with a low stress, the value of fractal dimension D rapidly grew and the fractal dimensions D of various samples tended to be stabilized after the stress reached to a high level.

ACS Style

Bo Li; Yunpei Liang; Lei Zhang; Quanle Zou. Breakage law and fractal characteristics of broken coal and rock masses with different mixing ratios during compaction. Energy Science & Engineering 2019, 7, 1000 -1015.

AMA Style

Bo Li, Yunpei Liang, Lei Zhang, Quanle Zou. Breakage law and fractal characteristics of broken coal and rock masses with different mixing ratios during compaction. Energy Science & Engineering. 2019; 7 (3):1000-1015.

Chicago/Turabian Style

Bo Li; Yunpei Liang; Lei Zhang; Quanle Zou. 2019. "Breakage law and fractal characteristics of broken coal and rock masses with different mixing ratios during compaction." Energy Science & Engineering 7, no. 3: 1000-1015.

Research article
Published: 19 March 2019 in Energy Science & Engineering
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The increase in extraction height will increase the mining‐induced overlying strata failure height. In this scenario, the strata pressure behavior is strong in a fully mechanized face with large mining height (FMFLMH), which frequently causes coal wall falls, roof falls, and hydraulic support failure accidents (e.g., support closure and hydraulic column damage). The key to solving these issues is to determine support's working resistance of the FMFLMH. In this paper, comprehensive theoretical analysis, numerical simulation, and field observation were applied to determine the support's working resistance in the FMFLMH based on movement type of the first subordinate key stratum (SKS 1). First, six kinds of movement types of SKS 1 in the FMFLMH are found and defined by theoretical analysis and numerical simulation, which are the direct caving movement type of cantilever structure (direct caving), the double‐sided rotation movement type of cantilever structure (double‐side rotation), the quadratic rotation movement type of cantilever structure (quadratic rotation), the alternative movement type of cantilever structure hinged structure (alternate hinged), the voussoir beam structure movement type (voussoir), and the short voussoir beam structure movement type (short voussoir), respectively. Besides, based on this, the support load calculation model of each movement type was established, and a formula for the support working resistance of each movement type was obtained. Finally, the correctness of the formulae for the support working resistance under six types of movement of SKS 1 were verified using measurement data from four FMFLMHs in China. These research results have important guiding significance for reasonable selection of support and ensuring safe mining of the FMFLMH.

ACS Style

Bo Li; Yunpei Liang; Quanle Zou. Determination of working resistance based on movement type of the first subordinate key stratum in a fully mechanized face with large mining height. Energy Science & Engineering 2019, 7, 777 -798.

AMA Style

Bo Li, Yunpei Liang, Quanle Zou. Determination of working resistance based on movement type of the first subordinate key stratum in a fully mechanized face with large mining height. Energy Science & Engineering. 2019; 7 (3):777-798.

Chicago/Turabian Style

Bo Li; Yunpei Liang; Quanle Zou. 2019. "Determination of working resistance based on movement type of the first subordinate key stratum in a fully mechanized face with large mining height." Energy Science & Engineering 7, no. 3: 777-798.

Research article
Published: 19 March 2019 in Advances in Civil Engineering
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The isothermal adsorption experiment of coal is an important method to study the mechanism of coal gas desorption. The orthogonal experiment is used to compare the gas desorption mechanism of coal under multifactor conditions, such as the particle size, temperature, pressure, moisture content, and molding pressure. The sensitivity of five factors was used to conduct regression analysis. The sensitivity and influence degree of five factors on the coal gas desorption capacity were analyzed. The results showed the following: (1) the effect of the coal sample particle size, temperature, pressure, moisture content, and molding pressure of coal on the sensitivity of desorption capacity is shown as C (pressure) > B (temperature) > A (particle size) > D (moisture content) > E (molding pressure); (2) the regression analysis of various factors for gas adsorption indicates that the degree of correlation of the multivariate quadratic regression equation is higher compared to that of the multivariate one-time regression equation; and (3) the coal sample particle size, temperature, pressure, moisture content, and type of gas desorption can well represent the gas desorption capacity of a coal sample under various conditions. The smaller the particle size of the coal sample, the higher the ambient temperature, the higher the gas pressure, the lower the moisture content of the coal sample, and the greater the gas desorption per unit mass in 30 min after coal sample gas adsorption equilibrium. The orthogonal test results have important theoretical significance for guiding gas adsorption and desorption tests of coal. For coal and gas outburst prediction, the coal seam gas flow mechanism, coal gas content prediction, and calculation of the mining coal gas emission have important practical significance for gas explosion accident prevention.

ACS Style

Fakai Wang; Yunpei Liang; Xuelong Li; Lei Li; Jianggong Li; Yulong Chen. Orthogonal Experimental Study on Multifactor Conditions for Gas Desorption in Coal. Advances in Civil Engineering 2019, 2019, 1 -12.

AMA Style

Fakai Wang, Yunpei Liang, Xuelong Li, Lei Li, Jianggong Li, Yulong Chen. Orthogonal Experimental Study on Multifactor Conditions for Gas Desorption in Coal. Advances in Civil Engineering. 2019; 2019 ():1-12.

Chicago/Turabian Style

Fakai Wang; Yunpei Liang; Xuelong Li; Lei Li; Jianggong Li; Yulong Chen. 2019. "Orthogonal Experimental Study on Multifactor Conditions for Gas Desorption in Coal." Advances in Civil Engineering 2019, no. : 1-12.

Research article
Published: 12 March 2019 in Energy Science & Engineering
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Coal‐like sampling obtained through compression molding is an important application of powder compression molding technology in mining engineering. To obtain ideal coal‐like samples for the revelation of the seepage property of low‐permeability soft coals, gas seepage studies, which utilized the Taguchi method, were performed on coal‐like materials with different particle sizes, activated carbon weight, Portland cement weight, and forming pressure. The effect of a single factor on the fluid‐solid coupling property of coal‐like materials was analyzed. The results indicate that the permeability and axial stress curves that correlated with strain in the conventional triaxial tests can be divided into three clear phases, and that layered damage appears in all tested specimens. The stress‐permeability relationship model of coal‐like materials is proposed. The influence of process parameters on the strength and permeability of coal briquettes during gas seepage tests was experimentally investigated. The Taguchi method and gray correlation analysis were integrated to determine the best combination of input factors through the key indicator of the gray relational grade, which is required to satisfy multiple quality goals in gas seepage coal‐like materials. The contribution percentage of the input factors to the outputs was determined using analysis of variance; it indicated that coal particle size was the prominent influencing parameter followed by activated carbon, forming pressure, and Portland cement.

ACS Style

Qingmiao Li; Yunpei Liang; Quanle Zou. Modeling the relationship between the influencing factors and the multiple responses of coal‐like materials using Taguchi‐Gray correlation analysis for their utilization in gas seepage studies. Energy Science & Engineering 2019, 7, 835 -850.

AMA Style

Qingmiao Li, Yunpei Liang, Quanle Zou. Modeling the relationship between the influencing factors and the multiple responses of coal‐like materials using Taguchi‐Gray correlation analysis for their utilization in gas seepage studies. Energy Science & Engineering. 2019; 7 (3):835-850.

Chicago/Turabian Style

Qingmiao Li; Yunpei Liang; Quanle Zou. 2019. "Modeling the relationship between the influencing factors and the multiple responses of coal‐like materials using Taguchi‐Gray correlation analysis for their utilization in gas seepage studies." Energy Science & Engineering 7, no. 3: 835-850.

Research article
Published: 08 January 2019 in Energy Science & Engineering
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The permeability characteristics of gas‐containing coal under different radial stress, different axial stress, and gas pressure were studied by orthogonal experiments, using a self‐developed three‐axis servo fluid infiltration system with a gas‐solid coupling of gas‐containing coal, on the basis of a single‐factor influence on the permeability of gas‐containing coal. By considering the effective stress, three kinds of relationships between permeability and radial stress, permeability and axial stress, as well as permeability and gas pressure were established. The results show that radial stress, axial stress, and gas pressure have a great influence on the permeability characteristics of gas‐containing coal: (a) The influence of radial stress on gas permeability is significant, whereas the influence of axial stress is negligible. The degree of influence of radial stress, gas pressure, and axial stress on the permeability decreases in turn; (b) The permeability decreases following a power function with the increase of the radial stress; (c) The permeability gradually increases with the increase of axial stress. With the increase of axial stress, the permeability increases following a power function; (d) The increase in gas pressure will reduce the effective stress on the coal, and the number of pores and cracks inside the coal body will decrease. This will increase the effective seepage flow and gas flow rate of the gas and eventually lead to the increase of coal permeability. There is a quadratic function relationship between the permeability and gas pressure.

ACS Style

Fakai Wang; Yunpei Liang; Xuelong Li; Lei Li; Jiangong Li; Yulong Chen. Study on the change of permeability of gas-containing coal under many factors. Energy Science & Engineering 2019, 7, 194 -206.

AMA Style

Fakai Wang, Yunpei Liang, Xuelong Li, Lei Li, Jiangong Li, Yulong Chen. Study on the change of permeability of gas-containing coal under many factors. Energy Science & Engineering. 2019; 7 (1):194-206.

Chicago/Turabian Style

Fakai Wang; Yunpei Liang; Xuelong Li; Lei Li; Jiangong Li; Yulong Chen. 2019. "Study on the change of permeability of gas-containing coal under many factors." Energy Science & Engineering 7, no. 1: 194-206.

Journal article
Published: 31 December 2018 in Processes
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The characteristics of the pore structure and gas migration in soft coalbeds are the premise of evaluating gas discharge in soft coalbeds. To explore the pore structure characteristics of soft coal masses, the No. 5 soft coalbed in the eastern zone of Chenghe Mining Area, was investigated and compared with the No. 5 hard coalbed in the western zone. By using a mercury intrusion method, low-temperature liquid nitrogen adsorption, and scanning electron microscopy (SEM), the pore structure characteristics of the No. 5 coalbed were explored. Moreover, based on fractal theory, the pore structure of coal was characterized. The results showed the pores in soft coal mainly appeared as small pores and micropores in which the small pores accounted for nearly half of the total pore volume. Mesopores and macropores were also distributed throughout the soft coal. The mercury-injection and mercury-ejection curves of soft coal showed significant hysteresis loops, implying that pores in coal samples were mainly open while the mercury-injection curve of hard coal was consistent with its mercury-ejection curve, showing no hysteresis loop while having an even segment, which indicated that closed pores occupied the majority of the pore volume in the coal samples. The curves of low-temperature nitrogen adsorption of soft coal all follow an IV-class isotherm. Moreover, the fractal dimensions of soft coal are respectively larger than the fractal dimensions of hard coal. It can be seen that the characterization of pores and fractures of the soft coal was different from the hard coal in the western distinct of the old mining area. The gas prevention and control measures of soft coal should be formulated according to local conditions.

ACS Style

Pan Wei; Yunpei Liang; Song Zhao; Shoujian Peng; Xuelong Li; Ran Meng. Characterization of Pores and Fractures in Soft Coal from the No. 5 Soft Coalbed in the Chenghe Mining Area. Processes 2018, 7, 13 .

AMA Style

Pan Wei, Yunpei Liang, Song Zhao, Shoujian Peng, Xuelong Li, Ran Meng. Characterization of Pores and Fractures in Soft Coal from the No. 5 Soft Coalbed in the Chenghe Mining Area. Processes. 2018; 7 (1):13.

Chicago/Turabian Style

Pan Wei; Yunpei Liang; Song Zhao; Shoujian Peng; Xuelong Li; Ran Meng. 2018. "Characterization of Pores and Fractures in Soft Coal from the No. 5 Soft Coalbed in the Chenghe Mining Area." Processes 7, no. 1: 13.

Journal article
Published: 14 November 2018 in Processes
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Coalbed gas content is the most important parameter for forecasting and preventing the occurrence of coal and gas outburst. However, existing methods have difficulty obtaining the coalbed gas content accurately. In this study, a numerical calculation model for the rapid estimation of coal seam gas content was established based on the characteristic values of gas desorption at specific exposure times. Combined with technical verification, a new method which avoids the calculation of gas loss for the rapid estimation of gas content in the coal seam was investigated. Study results show that the balanced adsorption gas pressure and coal gas desorption characteristic coefficient (Kt) satisfy the exponential equation, and the gas content and Kt are linear equations. The correlation coefficient of the fitting equation gradually decreases as the exposure time of the coal sample increases. Using the new method to measure and calculate the gas content of coal samples at two different working faces of the Lubanshan North mine (LBS), the deviation of the calculated coal sample gas content ranged from 0.32% to 8.84%, with an average of only 4.49%. Therefore, the new method meets the needs of field engineering technology.

ACS Style

Fakai Wang; Xusheng Zhao; Yunpei Liang; Xuelong Li; Yulong Chen. Calculation Model and Rapid Estimation Method for Coal Seam Gas Content. Processes 2018, 6, 223 .

AMA Style

Fakai Wang, Xusheng Zhao, Yunpei Liang, Xuelong Li, Yulong Chen. Calculation Model and Rapid Estimation Method for Coal Seam Gas Content. Processes. 2018; 6 (11):223.

Chicago/Turabian Style

Fakai Wang; Xusheng Zhao; Yunpei Liang; Xuelong Li; Yulong Chen. 2018. "Calculation Model and Rapid Estimation Method for Coal Seam Gas Content." Processes 6, no. 11: 223.

Journal article
Published: 01 July 2018 in Process Safety and Environmental Protection
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ACS Style

Yunpei Liang; Fakai Wang; Xuelong Li; Chenglin Jiang; Lei Li; Yulong Chen. Study on the influence factors of the initial expansion energy of released gas. Process Safety and Environmental Protection 2018, 117, 582 -592.

AMA Style

Yunpei Liang, Fakai Wang, Xuelong Li, Chenglin Jiang, Lei Li, Yulong Chen. Study on the influence factors of the initial expansion energy of released gas. Process Safety and Environmental Protection. 2018; 117 ():582-592.

Chicago/Turabian Style

Yunpei Liang; Fakai Wang; Xuelong Li; Chenglin Jiang; Lei Li; Yulong Chen. 2018. "Study on the influence factors of the initial expansion energy of released gas." Process Safety and Environmental Protection 117, no. : 582-592.

Research article
Published: 07 June 2018 in Adsorption Science & Technology
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Coal and gas outburst is a dynamic phenomenon with violent eruptions of coal and gas from the working coal seam. It has been proved that the rapid desorption within a short period is necessary for the occurrence of an outburst. Due to limitation of the present test condition, gas desorption characterization for the first 60 s has not been researched sufficiently. In the present study, an experimental apparatus with the ability of high-frequency data collection was developed. Initial desorption characterization of methane and carbon dioxide in coal was experimentally studied. Both the initial desorption characterization of methane and carbon dioxide were experimentally studied with different equilibrium pressures. The desorbed gas pressure was measured at desorption time phase of 0–10 and 45–60 s, besides the initial amount of desorbed gas and initial diffusion velocity of coal gas were calculated to assess their risk of outburst. The results show that the gas pressure for both methane and carbon dioxide increases sharply in the initial time and then levels off, and the total amount of desorbed gas increases with the increasing desorption time. Although the amount of desorption methane is slightly larger than that of carbon dioxide at the beginning, the total amount of desorbed carbon dioxide is significantly larger than that of methane at the desorption process. Therefore, it can be concluded that the coal and carbon dioxide outburst is more dangerous than the coal and methane outburst based on the obtained experimental results.

ACS Style

Yunpei Liang; Fakai Wang; Yongjiang Luo; Qianting Hu. Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction. Adsorption Science & Technology 2018, 36, 1484 -1495.

AMA Style

Yunpei Liang, Fakai Wang, Yongjiang Luo, Qianting Hu. Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction. Adsorption Science & Technology. 2018; 36 (7-8):1484-1495.

Chicago/Turabian Style

Yunpei Liang; Fakai Wang; Yongjiang Luo; Qianting Hu. 2018. "Desorption characterization of methane and carbon dioxide in coal and its influence on outburst prediction." Adsorption Science & Technology 36, no. 7-8: 1484-1495.

Research article
Published: 09 June 2017 in Environmental Science and Pollution Research
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Coalbed methane (CBM) recovery is a crucial approach to realize the exploitation of a clean energy and the reduction of the greenhouse gas emission. In the past 10 years, remarkable achievements on CBM recovery have been obtained in China. However, some key difficulties still exist such as long borehole drilling in complicated geological condition, and poor gas drainage effect due to low permeability. In this study, intelligent and integrated techniques for CBM recovery are introduced. These integrated techniques mainly include underground CBM recovery techniques and ground well CBM recovery techniques. The underground CBM recovery techniques consist of the borehole formation technique, gas concentration improvement technique, and permeability enhancement technique. According to the division of mining-induced disturbance area, the ground well arrangement area and well structure type in mining-induced disturbance developing area and mining-induced disturbance stable area are optimized to significantly improve the ground well CBM recovery. Besides, automatic devices such as drilling pipe installation device are also developed to achieve remote control of data recording, which makes the integrated techniques intelligent. These techniques can provide key solutions to some long-term difficulties in CBM recovery.

ACS Style

Hu Qianting; Liang Yunpei; Wang Han; Zou Quanle; Sun Haitao. Intelligent and integrated techniques for coalbed methane (CBM) recovery and reduction of greenhouse gas emission. Environmental Science and Pollution Research 2017, 24, 17651 -17668.

AMA Style

Hu Qianting, Liang Yunpei, Wang Han, Zou Quanle, Sun Haitao. Intelligent and integrated techniques for coalbed methane (CBM) recovery and reduction of greenhouse gas emission. Environmental Science and Pollution Research. 2017; 24 (21):17651-17668.

Chicago/Turabian Style

Hu Qianting; Liang Yunpei; Wang Han; Zou Quanle; Sun Haitao. 2017. "Intelligent and integrated techniques for coalbed methane (CBM) recovery and reduction of greenhouse gas emission." Environmental Science and Pollution Research 24, no. 21: 17651-17668.