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Regularity and mechanism of coal resistivity response with different conductive characteristics in complete stress-strain process

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International Journal of mining Science and Technology 2015年第5期25卷 779-786页

作者： Chen Peng Wang Enyuan Chen Xuexi Liu Zhentang Li Zhonghui Shen Rongxi School of Safety Engineering North China Institute of Science & Technology School of Safety Engineering China University of Mining & Technology key laboratory of Gas and Fire control for Coal Mines Ministry of Education

The stress,strain as well as resistivity of coal during uniaxial compression process were tested based on self-built real-time testing system of loaded coal ***,the coal resistivity regularity and mechanism were analyzed at different stages of complete stress-strain process,which includes the two kinds of coal body with typical conductive *** results indicate that coal resistivity with different conductive characteristics has different change rules in complete stress-strain *** is mainly represented at the densification and flexibility phases before dilatation *** variation of resistivity can be divided into two kinds,named down and *** of coal samples occurred between 66%σ_(max) and 87%σ_(max).Because of dilatation,coal resistivity involves sudden *** overall representation is shifting from reducing into improving or from slow improving into accelerated ***,coal resistivity always shows an increasing tendency at the plastic *** peak stress,coal body enters into failure *** expanding and communicating of macro fracture causes further improvement of coal *** maximum value of resistivity rangeability named λ reached *** making real-time monitoring on coal resistivity,variation rules of resistivity can be deemed as precursory information so as to reflect the dilatation and sudden change before coal body reaches buckling failure,which can provide a new technological means for forecasting the dynamic disaster of coal petrography.

关键词： Resistivity Stress-strain Dilatation Conductive characteristics Coal structure

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Characteristics of in situ stress field at Qingshui coal mine

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International Journal of mining Science and Technology 2015年第3期25卷 497-501页

作者： Yang Xiaojie Pang Jiewen Lou Haopeng Fan Lipeng State key laboratory of Geomechanics and Deep Underground Engineering China University of Mining & Technology School of Mechanics and Civil Engineering China University of Mining & Technology key laboratory of Deep mining and hazard Prevention China University of Mining & Technology

In this study, the characteristics of geological structure at Qingshui coal mine were analyzed. And the hollow inclusion strain cell overcoring method was used to obtain the in situ stress. The effect of in situ stress on the stability of soft rock roadway was analyzed. The results show that the maximum principal stress is in the horizontal direction with a northeast orientation and has a value of about 1.2–1.9 times larger than gravity; the right side of roadway roof and floor is easily subject to serious deformation and failure, and the in situ stress is found to be a major factor. This paper presents important information for developing countermeasures against the large deformation of the soft rock roadway at Qingshui coal mine.

关键词： Soft rockIn situ stress Overcoring method Roadway stability

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Predicting microseismic,acoustic emission and electromagnetic radiation data using neural networks

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 616-629页

作者： Yangyang Di Enyuan Wang Zhonghui Li Xiaofei Liu Tao Huang Jiajie Yao School of Materials Engineering Changshu Institute of TechnologySuzhou215506China key laboratory of Gas and Fire control for Coal Mines(china University of mining and Technology) Ministry of EducationXuzhou221116China School of Safety Engineering China University of Mining and TechnologyXuzhou221116China State key laboratory of Coal Resources and Safe mining China University of Mining and TechnologyXuzhou221116China

Microseism,acoustic emission and electromagnetic radiation(M-A-E)data are usually used for predicting rockburst ***,it is a great challenge to realize the prediction of M-A-E *** this study,with the aid of a deep learning algorithm,a new method for the prediction of M-A-E data is *** this method,an M-A-E data prediction model is built based on a variety of neural networks after analyzing numerous M-A-E data,and then the M-A-E data can be *** predicted results are highly correlated with the real data collected in the *** field verification,the deep learning-based prediction method of M-A-E data provides quantitative prediction data for rockburst monitoring.

关键词： Microseism Acoustic emission Electromagnetic radiation Neural networks Deep learning Rockburst

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Robust Offline Actor-Critic With On-policy Regularized Policy Evaluation

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IEEE/CAA Journal of Automatica Sinica 2024年第12期11卷 2497-2511页

作者： Shuo Cao Xuesong Wang Yuhu Cheng the Engineering Research Center of Intelligent control for Underground Space Ministry of Education and the School of Information and Control Engineering China University of Mining and Technology IEEE

To alleviate the extrapolation error and instability inherent in Q-function directly learned by off-policy Q-learning(QL-style) on static datasets, this article utilizes the on-policy state-action-reward-state-action(SARSA-style) to develop an offline reinforcement learning(RL) method termed robust offline Actor-Critic with on-policy regularized policy evaluation(OPRAC). With the help of SARSA-style bootstrap actions, a conservative on-policy Q-function and a penalty term for matching the on-policy and off-policy actions are jointly constructed to regularize the optimal Q-function of off-policy QL-style. This naturally equips the off-policy QL-style policy evaluation with the intrinsic pessimistic conservatism of on-policy SARSA-style, thus facilitating the acquisition of stable estimated Q-function. Even with limited data sampling errors, the convergence of Q-function learned by OPRAC and the controllability of bias upper bound between the learned Q-function and its true Q-value can be theoretically guaranteed. In addition, the sub-optimality of learned optimal policy merely stems from sampling errors. Experiments on the well-known D4RL Gym-MuJoCo benchmark demonstrate that OPRAC can rapidly learn robust and effective tasksolving policies owing to the stable estimate of Q-value, outperforming state-of-the-art offline RLs by at least 15%.

关键词： Offline reinforcement learning off-policy QL-style on-policy SARSA-style policy evaluation (PE) Q-value estimation

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Enhancing the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect with sodium dodecyl sulfate surfactant

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International Journal of mining Science and Technology 2021年第6期31卷 995-1002页

作者： Yongbing Zhang Boyuan Zhang Siqi Yang Zhigang Zhong Hepeng Zhou Xianping Luo Jiangxi key laboratory of mining&Metallurgy Environmental Pollution control Ganzhou 341000China key laboratory of Ionic Rare Earth Resources Development and Application Ministry of EducationGanzhou 341000China Faculty of Resource and Environmental Engineering Jiangxi University of Science and TechnologyGanzhou 341000China

Ameliorating the problem of low leaching efficiency,long leaching period,and high agent consumption should be studied to efficiently exploit ion-absorbed rare earth ore *** this study,the surfactant sodium dodecyl sulfate(SDS) is used to enhance the leaching effect of an ion-absorbed rare earth ore by ameliorating the seepage effect for the first *** effects of surfactant concentration,leaching agent dosage,solution flow velocity,and solution pH on the leaching rate were explored,and the mechanism of SDS was *** the optimum conditions,the addition of a small amount of SDS(mass fraction0.04%) can increase the leaching rate by about 5%,shorten the leaching period,and reduce the consumption of the leaching *** significantly ameliorates the seepage effect of the ore body by reducing the surface tension of the leaching agent and ameliorating the wettability of the mineral *** effect is the main factor that improves the leaching ***(density functional theory) calculation results show that SDS can react with rare earth ions,which reduces the adsorption strength on clay mineral ***,rare earth ions are easily exchanged by ammonium ions,and mass transfer is enhanced.

关键词： Ion-absorbed rare earth ore Surfactant Sodium dodecyl sulfate Leaching Seepage effect Adsorption

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Experimental and numerical study of failure behavior and mechanism of coal under dynamic compressive loads

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International Journal of mining Science and Technology 2020年第5期30卷 613-621页

作者： Junjun Feng Enyuan Wang Qisong Huang Houcheng Ding Xiangyang Zhang Civil Engineering and Architecture Anhui University of TechnologyMaanshanAnhui 243002China key laboratory of Safety and High-efficiency Coal mining Ministry of EducationAnhui University of Science and TechnologyHuainanAnhui 232001China State key laboratory Cultivation Base for Gas Geology and Gas control Henan Polytechnic UniversityJiaozuoHenan 454003China key laboratory of Gas and Fire control for Coal Mines China University of Mining and TechnologyXuzhouJiangsu 221116China

A comprehensive understanding of the failure behavior and mechanism of coal is a prerequisite for dealing with dynamic problems in mining *** this study,the failure behavior and mechanism of coal under uniaxial dynamic compressive loads were experimentally and numerically *** experiments were conducted using a split Hopkinson pressure bar(SHPB)*** results indicated that the typical failure of coal is lateral and axial at lower loading rates and totally smashed at higher loading *** further fractography analysis of lateral and axial fracture fragments indicated that the coal failure under dynamic compressive load is caused by tensile brittle *** addition,the typical failure modes of coal under dynamic load were numerically *** numerical results indicated that the axial fracture is caused directly by the incident compressive stress wave and the lateral fracture is caused by the tensile stress wave reflected from the interface between coal specimen and transmitted *** application was further conducted to interpret dynamic problems in underground coal mine and it manifested that the lateral and axial fractures of coal constitute the parallel cracks in the coal mass under roof fall and blasting in mining space.

关键词： Split Hopkinson pressure bar Stress wave Failure mode Fracture mechanism Fractography

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Method for designing the optimal sealing depth in methane drainage boreholes to realize efficient drainage

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International Journal of Coal Science & Technology 2021年第6期8卷 1400-1410页

作者： Minghao Yi Liang Wang Congmeng Hao Qingquan Liu Zhenyang Wang key laboratory of Coal Methane and Fire control Ministry of EducationChina University of Mining and TechnologyXuzhou 221116JiangsuChina National Engineering Research Center for Coal Gas control China University of Mining and TechnologyXuzhou 221116JiangsuChina School of Safety Engineering China University of Mining and TechnologyXuzhou 221116JiangsuChina

The purpose of underground methane drainage technology is to prevent methane disasters and enable the efficient use of coal mine methane(CMM),and the sealing depth is a key factor that affects the performance of underground methane *** this work,the layouts of in-seam and crossing boreholes are considered to analyze the stress distribution and failure characteristics of roadway surrounding rock through a numerical simulation and field stress investigation to determine a reasonable sealing *** results show that the depths of the plastic and elastic zones in two experimental coal mines are 16 and 20 m *** sealing minimizes the air leakage through the fractures around the roadway when the sealing material covers the failure and plastic zones,and the field test results for CMM drainage at different sealing depths indicate that the CMM drainage efficiency increases with increasing sealing depth but does not change once the sealing depth exceeds the plastic ***,sealing in the high-permeability roadway surrounding rock does not have a strong influence on the borehole sealing *** these findings,a new CMM drainage system for key sealing in the low-permeability zone was developed that is effective for improving the CMM drainage efficiency and prolonging the high-concentration CMM drainage *** proposed approach offers a valuable quantitative analysis method for selecting the optimum sealing parameters for underground methane drainage,thereby improving considerably the drainage and utilization rates of CMM.

关键词： Coal mine methane Methane drainage Borehole sealing mining safety Methane utilization

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Experimental study on permeability evolution of deep high-stressed coal under major horizontal stress unloading paths

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International Journal of mining Science and Technology 2024年第11期34卷 1495-1508页

作者： Liu, Chao Zhang, Jiahao Wu, Songwei Qi, Jinghua Yu, Beichen Wang, Liang School of Mechanics and Civil Engineering China University of Mining and Technology Xuzhou 221116 China State key laboratory of mining Disaster Prevention and control Ministry of Education Shandong University of Science and Technology Qingdao 266590 China School of Safety Engineering China University of Mining and Technology Xuzhou 221116 China State key laboratory of Coal Mine Disaster Prevention and control China University of Mining and Technology Xuzhou 221116 China key laboratory of Theory and Technology on Coal and Rock Dynamic Disaster Prevention and control National Mine Safety Administration China University of Mining and Technology Xuzhou 221116 China

Both bulk stress (σii) and stress path (SP) significantly affect the transportation characteristics of deep gas during reservoir pressure depletion. Therefore, the experimental study of horizontal stress unloading on seepage behavior of gas-bearing coal under constant σii-constraints is performed. The results show that coal permeability is affected by horizontal stress anisotropy (σH≠σh), and the contribution of minor horizontal stress to permeability is related to the differential response of horizontal strain. The slippage phenomenon is prominent in deep high-stress regime, especially in low reservoir pressure. σii and SP jointly determine the manifestation of slippage effect and the strength of stress sensitivity (γ) of permeability. Deep reservoir implies an incremental percentage of slip-based permeability, and SP weakens the slippage effect by changing the elastic–plastic state of coal. However, γ is negatively correlated with slippage effect. From the Walsh model, narrow (low aspect-ratio) fractures within the coal under unloading SP became the main channel for gas seepage, and bring the effective stress coefficient of permeability (χ) less than 1 for both low-stress elastic and high-stress damaged coal. With the raise of the effective stress, the effect of pore-lined clay particles on permeability was enhanced, inducing an increase in χ for high-stress elastic coal. © 2024

关键词： Aspect ratio

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Accelerating leaching of copper ore with surfactant and the analysis of reaction kinetics

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International Journal of Minerals,Metallurgy and Materials 2019年第3期26卷 274-281页

作者： Chun-ming Ai Ping-ping Sun Ai-xiang Wu Xun Chen Chao Liu College of Safety Science and Engineering Liaoning Technical University key laboratory of ministry of education of china for Efficient mining and Safety of Metal Mines University of Science and Technology Beijing Wanbao mining Limited

To solve the problem of low permeability and lower extraction rates of high-mud ores, a surfactant was added as a penetrant to the pregnant leaching solution during column leaching tests. On the basis of the theories of physical chemistry and seepage flow mechanics, the mechanism by which seepage is enhanced under the effects of the surfactant was analyzed. The results show that the action modes of the surfactant were divided into four aspects: changing the wettability of the ore, reducing the viscosity of the leaching solution, adsorbing onto the surface of ore, and enhancing the permeability effect. The findings of column leaching tests demonstrated that permeability was substantially improved by the surfactant. In the later period of leaching, the permeability coefficient was two times higher than that of the control group. Meanwhile, the ore extraction rate increased by approximately 10%. During the leaching process, the surface tension of the solution did not substantially change, and that of the solution with surfactant increased slightly. The kinetics analysis of ore column leaching illustrated that the leaching processes were controlled by both internal diffusion(principal factor) and chemical reaction.

关键词： surfactant permeability reaction kinetics leaching

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Strata movement and stress evolution when mining two overlapping panels affected by hard stratum

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International Journal of mining Science and Technology 2019年第5期29卷 691-699页

作者： Jianguo Zhang Wei Yang Baiquan Lin Jinjing Zhang Man Wang State key laboratory of Coking Coal Exploitation and Comprehensive Utilization China Pingmei Shenma GroupPingdingshan 467000China key laboratory of Gas and Fire control for Coal Mines(china University of mining and Technology) Ministry of EducationXuzhou 221116China china Pingmei Shenma Group Pingdingshan 467000China School of Safety Engineering China University of Mining and TechnologyXuzhou 221116China

mining causes stress redistribution and stratum *** this paper,a numerical model was built according to the geological conditions in the 12th coal mine in Pingdingshan city to study the strata movement and the evolution of stress when mining two overlapping longwall panels,named panels#14 and#*** strata close to the mined panel move directly towards the gob,while the strata that are farther away swing back and forth during the mining *** directed movement and swinging can break the transverse boreholes for gas extraction;a surface borehole should not be within the range of directional *** stress evolution suggested that the mining of the lower panel#15 after the upper panel#14 would further increase the de-stressed range,while the stress concentration around the mined panel would be *** strata usually carry a greater stress than adjacent rocks and soft coal *** stress in a hard stratum increases greatly,and the stress decreases greatly in the coal seams below the hard *** study supplies a reference for similar coal mines and is useful for determining the de-stressed range and transverse borehole arrangement for gas extraction.

关键词： Stratum movement mining Longwall panel Hard stratum

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