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Dynamic leakage mechanism of gas drainage borehole and engineering application

International Journal of Mining Science and Technology 2018年第3期28卷 505-512页

作者： Zhang Junxiang Li Bo Sun Yuning School of Energy Science and engineering Henan Polytechnic University Jiaozuo 454003 China state Key laboratory Cultivation Base for gas Geology and gas control Henan Polytechnic University Jiaozuo 454003 China Collaborative Innovation Center of Coal Safety Production of Henan Province Jiaozuo 454003 China state and local joint engineering laboratory for gas drainage & ground control of deep mines Henan Polytechnic University fiaozuo 454003 China

Borehole leakage not only affects the gas drainage effect but also presents considerable risk to human security. For the research on the leakage mechanism of gas drainage borehole, the rheological and visco-elastic-plastic characteristics were considered to establish the mechanical model of coal mass around borehole, which is used to analyze the leakage mechanism and deduce the dynamic leakage model. On the basis of the real coal seam conditions, the variation rules of the stress, leakage ring, and air leakage amount were analyzed through numerical simulation, and the influence factors of air leakage amount were also investigated to provide the theoretical basis for the sealing technology. Results show that the air leakage amount of borehole is inversely proportional to the increase in supporting stress and sealing length, and directly correlated with the increase in borehole radius and softening modulus. Using theoretical analysis, we design a novel active supporting sealing technology that can use grouting material to seal the fractures to reduce the leakage channels and also provide supporting stress to prevent borehole deformation. The engineering test results indicate that the average gas concentration with the novel active supporting sealing technology is increased by 162.12% than that of traditional polyurethane sealing method. Therefore, this technology not only effectively resolves borehole leakage but also significantly improves the gas drainage effect.

关键词： Borehole leakage gas drainage Leakage mechanism Numerical simulation Supporting stress

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Structure and deformation measurements of shallow overburden during top coal caving longwall mining

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International Journal of Mining Science and Technology 2017年第6期27卷 1081-1085页

作者： Li Sheng Fan Chaojun Luo Mingkun Yang Zhenhua Lan Tianwei Zhang Haifeng College of Mining Liaoning Technical University state and local joint engineering laboratory for gas drainage & ground control of deep mines Henan Polytechnic University state Key laboratory of Coal Resources and Safe Mining China University of Mining & Technology Chengyi Coal Mine Inner Mongolia Yitai Coal Co.Ltd.

Mining induced pressures are strong and overburden failure areas are large in top coal caving longwall mining, which constrains high production and safety mining. By employing the combination of the full view borehole photography technique and the seismic CT scanner technique, the deformation and failure of overlying strata of fully mechanized caving face in shallow coal seam were studied and the failure development of overburden was determined. Results show that the full view borehole photography can reveal the characteristics of strata, and the seismic CT scanner can reflect the characteristics of strata between the boreholes. The combined measurement technique can effectively determine the height of fractured and caved zones. The top end of the caved zone in Yangwangou coal mine employing the top coal caving longwall mining was at the depth of 171 m and fractured zone was at the depth of 106-110 m. The results provide a theoretic foundation for controlling the overburden strata in the shallow buried top coal caving panel.

关键词： Top coal caving Shallow depth Overburden failure and deformation Full view borehole photography Seismic CT scanner

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Rockburst mechanism and the law of energy accumulation and release in mining roadway: a case study

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International Journal of Coal Science & Technology 2022年第5期9卷 96-112页

作者： Feng Du Ji Ma Xiaofei Guo Tianfeng Wang Xiaohang Dong Jiashuo Li Shulei He Dilinaer Nuerjuma Beijing Key laboratory for Precise Mining of Intergrown Energy and Resources China University of Mining and Technology(Beijing)100083 BeijingChina state and local joint engineering laboratory for gas drainage&ground control of deep mines Henan Polytechnic University454003 JiaozuoHenanChina School of Safety Science and engineering Henan Polytechnic University454003 JiaozuoHenanChina

The rockburst dynamic disasters in the process of deep coal mining become more and more *** the rockburst occurred in the 23130 working face of Yuejin Coal Mine as the engineering background,we study the characteristics of mining stress feld around roadway,the plastic failure morphological characteristics of surrounding rock and the accumulation/release law of elastic energy before and after *** analysis model quantitatively describing the physical process of rockburst in the mining roadway is established,and the calculation method of dynamic release of elastic energy in the physical process of rockburst is *** mechanism of rockburst in mining roadway is *** results show that an“L-shaped”stress concentration zone is formed within 100 m of the 23130 working face,and the principal stress ratio of the surrounding rock of the transportation roadway is 2.59–*** change of the direction of the maximum principal stress has a signifcant efect on the burst appearance *** failure strength of diferent sections of the mining roadway is characterized by the elastic energy release *** the increase of the working face distance,the elastic energy released by burst failure and the expansion variation of failure boundary radius show a nonlinear variation law that tends to decrease steadily after sharp *** closer to the working face,the higher the burst *** a distance of 10 m from the working surface,the maximum principal stress reaches its maximum *** butterfy-shaped failure system generated by the surrounding rock of the roadway has energy self-sustainability,and the elastic energy released by the sudden expansion of the butterfy leaf is enough to cause a burst damage of 1.9 *** work could provide theoretical support for the prediction and prevention of rockburst.

关键词： Coal Rockburst Mining roadway Plastic failure Dynamic and static load Elastic energy

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Regression analysis of major parameters affecting the intensity of coal and gas outbursts in laboratory

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International Journal of Mining Science and Technology 2017年第2期27卷 327-332页

作者： Geng Jiabo Xu Jiang Nie Wen Peng Shoujian Zhang Chaolin Luo Xiaohang state Key laboratory of Coal Mine Disaster Dynamics and control Chongqing UniversityChongqing 400044China state and local joint engineering laboratory of Methane drainage in Complex Coal gas Seam Chongqing UniversityChongqing 400044China

Estimating the intensity of outbursts of coal and gas is important as the intensity and frequency of outbursts of coal and gas tend to increase in deep mining. Fully understanding the major factors contributing to coal and gas outbursts is significant in the evaluation of the intensity of the outburst. In this paper, we discuss the correlation between these major factors and the intensity of the outburst using Analysis of Variance(ANOVA) and Contingency Table Analysis(CTA). Regression analysis is used to evaluate the impact of these major factors on the intensity of outbursts based on physical experiments. Based on the evaluation, two simple models in terms of multiple linear and nonlinear regression were constructed for the prediction of the intensity of the outburst. The results show that the gas pressure and initial moisture in the coal mass could be the most significant factors compared to the weakest factor-porosity. The P values from Fisher's exact test in CTA are: moisture(0.019), geostress(0.290), porosity(0.650), and gas pressure(0.031). P values from ANOVA are moisture(0.094), geostress(0.077), porosity(0.420), and gas pressure(0.051). Furthermore, the multiple nonlinear regression model(RMSE: 3.870) is more accurate than the linear regression model(RMSE: 4.091).

关键词： Coal and gas outburst gas pressure Regression analysis ANOVA CTA

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Synthesis of nitrogen-doped reduced graphene oxide/magnesium ferrite/polyaniline composite aerogel as a lightweight,broadband and efficient microwave absorber

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Journal of Materials Science & Technology 2024年第8期175卷 115-124页

作者： Ruiwen Shu Lijuan Nie Ziwei Zhao Xunhong Yang School of Chemical engineering State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal MinesAnhui University of Science and TechnologyHuainan 232001China joint National-local engineering Research Centre for Safe and Precise Coal Mining Anhui University of Science and TechnologyHuainan 232001China

The fabrication of graphene-based microwave absorbing materials with low density,small filling ratio,broad bandwidth and strong absorption remains a huge *** this work,nitrogen-doped reduced graphene oxide/magnesium ferrite/polyaniline(NRGO/MgFe_(2)O_(4)/PANI)composite aerogel was synthesized by a three-step method of solvothermal reaction,in situ chemical oxidation polymerization and hydrothermal *** results showed that the obtained aerogels had a unique three-dimensional(3D)porous network structure and low bulk density(11.1-13.0 mg cm^(−3)).It was worth noting that in the NRGO/MgFe_(2)O_(4)/PANI ternary composite aerogel,MgFe_(2)O_(4)coated with a thin PANI layer was anchored on the surface of NRGO ***,the NRGO/MgFe_(2)O_(4)/PANI ternary composite aerogel showed much better microwave absorbing capacity compared with pure NRGO aerogel and NRGO/MgFe_(2)O_(4)binary composite *** the filling ratio was as low as 11.5 wt.%,the obtained ternary composite aerogel exhibited the maximum effective absorption bandwidth of 7.0 GHz at a matching thickness of 2.1 mm,and the minimum reflection loss of-42.9 dB at a thickness of 3.57 ***,the prob-able microwave dissipation mechanism was also *** was believed that this study would pave the way for the construction of 3D graphene-based composites as lightweight,broadband and efficient microwave absorbents.

关键词： Graphene Composite aerogel Polyaniline Magnesium ferrite Microwave absorption

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Mechanical responses and acoustic emission behaviors of coal under compressive differential cyclic loading(DCL):a numerical study via 3D heterogeneous particle model

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International Journal of Coal Science & Technology 2023年第3期10卷 136-154页

作者： Zhengyang Song Yunfeng Wu Yong Zhang Yi Yang Zhen Yang state Key laboratory of Water Resource Protection and Utilization in Coal Mining BeijingChina Department of Civil engineering University of Science&Technology BejingBeijing 100083China state Key laboratory of Mining Response and Disaster Prevention and control in deep Coal mines Anhui University of Science and TechnologyHuainan 232001China

The stability of coal walls(pillars)can be seriously undermined by diverse in-situ dynamic *** on a 3D par-ticle model,this work strives to numerically replicate the major mechanical responses and acoustic emission(AE)behaviors of coal samples under multi-stage compressive cyclic loading with different loading and unloading rates,which is termed differential cyclic loading(DCL).A Weibull-distribution-based model with heterogeneous bond strengths is constructed by both considering the stress-strain relations and AE *** previously loaded samples were respectively grouped to indicate two DCL regimes,the damage mechanisms for the two groups are explicitly characterized via the time-stress-dependent variation of bond size multiplier,and it is found the two regimes correlate with distinct damage patterns,which involves the competition between stiffness hardening and *** numerical b-value is calculated based on the mag-nitudes of AE energy,the results show that both stress level and bond radius multiplier can impact the numerical *** proposed numerical model succeeds in replicating the stress-strain relations of lab data as well as the elastic-after effect in DCL *** effect of damping on energy dissipation and phase shift in numerical model is summarized.

关键词： Differential cyclic loading(DCL) Particle model Acoustic emission(AE) Discrete element method(DEM)Damage mechanism

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Prospects for the transformation and development of carbon storage in abandoned mines of coal enterprises from the perspective ofcarbon neutrality

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International Journal of Coal Science & Technology 2023年第3期10卷 24-40页

作者： Xin Lyu Tong Zhang Liang Yuan Juejing Fang state Key laboratory of Mining Response and Disaster Prevention and control in deep Coal mines Anhui University of Science and TechnologyHuainan 232001China Institute of Energy Hefei Comprehensive National Science CenterHefei230031China

Under the carbon neutrality goal,coal enterprises must seek breakthroughs from abandoned mines,develop new resources in the new era,turn problems into countermeasures,and participate in the carbon emissions market,for contributing to the accomplishment of the national strategic goal of carbon *** this end,we investigated the relevant national policies and regulations to clarify the boundaries disclosed by the carbon information of enterprises,understood the development direction of carbon storage in abandoned mines,and clarified the transformation and development of carbon storage in aban-doned *** made a few suggestions:(1)China should learn from its past experience and other countries to develop the energy industry with Chinese characteristics and reform the economic system.(2)Coal enterprises must actively respond to the national carbon information disclosure policy,clarify their own responsibilities and carbon emission boundaries.(3)It is necessary to proactively obtain advanced knowledge and plan carbon storage pathways for abandoned mines.(4)Devel-opment problems of coal enterprises should be deduced using ***'dual carbon'goals should be achieved steadily step-by-step.(5)Three measures,*** the existing resource structure,coordinating the information of abandoned mines,and promoting the cultivation of scientific and technological talents.

关键词： Mining engineering Abandoned mines Carbon neutrality Carbon emission rights Carbon tax

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Fracture behavior and acoustic emission characteristics of sandstone samples with inclined precracks

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International Journal of Coal Science & Technology 2021年第1期8卷 77-87页

作者： Litong Dou Ke Yang Xiaolou Chi state Key laboratory of Mining Response and Disaster Prevention and control in deep Coal mines Anhui University of Science and TechnologyHuainan232001AnhuiChina Institute of Energy Hefei Comprehensive National Science CenterHefei230031AnhuiChina National and local joint engineering Research Center of Precision Coal Mining Anhui University of Science and TechnologyHuainan232001AnhuiChina Key laboratory of Mining Coal Safety and Efficiently Constructed by Anhui Province and Ministry of Education Anhui University of Science and TechnologyHuainan232001AnhuiChina

Sandstone samples with precracks of different dip angles were collected from a coal mine roof and subjected to uniaxial compression tests,and acoustic emission(AE)and scanning electron microscopy(SEM)were used to study how the crack dip angle affected the fracture *** the precracked sandstone samples,as the dip angle between the crack line and loading direction decreased,so did the peak stress and its completion *** SEM observations revealed a fracture transition from tensile cleavage to shear slip,which was manifested by a microstructure change from aggregate to *** to energy conversion,a decreased crack dip angle results in gradually decreasing total and dissipative peak energies,whose variation amplitudes at different stages are consistent with those of the peak stress of the *** decreased crack dip angle lowered the stress required to trigger the first appearance of AE energy peaks and ring-down counts,as well as shortening the period before the occurrence of the first AE peak ***,the AE energy and ring-down count during the failure stage after the stress peak increased gradually.A stepped increase was observed in the AE ring-down count curves,with each step corresponding to a jump in the stress-strain *** the characteristics of the AE signal of the fracture of a precracked rock sample,the occurrence of joints or faults in the rock mass can be reasonably *** is expected to provide a new method and approach for predicting coal and rock dynamic disasters.

关键词： Rock mechanics Precrack Fracture mode Energy conversion Acoustic emission

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Energy evolution and water immersion‑induced weakening in sandstone roof of coal mines

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International Journal of Coal Science & Technology 2022年第4期9卷 93-106页

作者： Wenjie Liu Ke Yang Shuai Zhang Zhainan Zhang Rijie Xu state Key laboratory of Mining Response and Disaster Prevention and control in deep Coal mines Anhui University of Science and TechnologyHuainan 232001China Hefei Comprehensive National Science Center Institute of EnergyHefei 230031AnhuiChina National and local joint engineering Research Center of Precision Coal Mining Anhui University of Science and TechnologyHuainan 232001AnhuiChina Key laboratory of Mining Coal Safety and Efciently Constructed By Anhui Province and Ministry of Education Anhui University of Science and TechnologyHuainan 232001China state Key laboratory of Coal Resources and Safe Mining China University of Mining and TechnologyXuzhou 221116JiangsuChina

The instability of underground spaces in abandoned coal mines with water-immersed rocks is one of the main hazards hindering the geothermal energy use and ecological restoration of post-mining *** study conducted graded cyclic loading–unloading tests of fve groups of sandstone samples with diferent water *** evolution of input,elastic,dissipated,damping,and plastic energies were explored,considering the damping *** normalized plastic energy serves to characterize the damage evolution of sandstone samples,whose failure characteristics were analyzed from both the macroscopic and microscopic perspectives.X-ray difraction technique and scanning electron microscopy were used to reveal the softening mechanism of *** results show that under graded cyclic loading,input energy,elastic energy,and dissipated energy all increase gradually,and the fraction of elastic energy increases gradually at frst and then tends to *** variation in the fraction of dissipated energy is opposite to that of elastic *** each cycle,the input energy is stored primarily in the form of elastic energy,whereas the dissipated energy is used primarily to overcome the damping of *** the normalized number of cycles approached unity,the plastic energy fraction sharply increases,while that of the dampening energy drops *** increasing water content,the efect of pore water on the lubrication,the water wedge,and dissolution of mineral particles becomes more obvious,reducing the elastic-storage limit of sandstone,meanwhile the sandstone damage factor increases signifcantly under the same cycle and the failure mode changes from brittle to ductile.

关键词： Mining engineering Energy evolution Water-rock interaction Weakening mechanism

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Experimental study on the deformation and failure mechanism of overburden rock during coal mining using a comprehensive intelligent sensing method

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Journal of Rock Mechanics and Geotechnical engineering 2022年第5期14卷 1626-1641页

作者： Gang Cheng Wentao Xu Bin Shi Jinghong Wu Binyang Sun Honghu Zhu School of Computer Science North China Institute of Science and TechnologyBeijing101601China School of Earth Sciences and engineering Nanjing UniversityNanjing210023China state Key laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu610059China School of Civil engineering Suzhou University of Science and TechnologySuzhou215009China state Key laboratory of Mining Response and Disaster Prevention and control in deep Coal mines Anhui University of Science and TechnologyHuainan232001China

Understanding the spatiotemporal evolution of overburden deformation during coal mining is still a challenge in engineering practice due to the limitation of monitoring techniques. Taking the Yangliu Coal Mine as an example, a similarity model test was designed and conducted to investigate the deformation and failure mechanism of overlying rocks in this study. Distributed fiber optic sensing(DFOS), highdensity electrical resistivity tomography(HD-ERT) and close-range photogrammetry(CRP) technologies were used in the test for comprehensive analyses. The combined use of the three methods facilitates the investigation of the spatiotemporal evolution characteristics of overburden deformation, showing that the mining-induced deformation of overburden strata was a dynamic evolution process. This process was accompanied by the formation, propagation, closure and redevelopment of separation ***, the key rock stratum with high strength and high-quality lithology played a crucial role in the whole process of overburden deformation. There were generally three failure modes of overburden rock layers, including bending and tension, overall shearing, and shearing and sliding. Shear failure often leads to overburden falling off in blocks, which poses a serious threat to mining safety. Therefore, realtime and accurate monitoring of overburden deformation is of great significance for the safe mining of underground coal seams.

关键词： Similarity model Distributed fiber optic sensing(DFOS) Overburden deformation Failure mechanism Coal seam mining

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