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Heat transfer and temperature evolution in underground mininginduced overburden fracture and ground fissures: Optimal time window of UAV infrared monitoring

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International Journal of mining Science and Technology 2024年第1期34卷 31-50页

作者： Yixin Zhao Kangning Zhang Bo Sun Chunwei Ling Jihong Guo Beijing Key Laboratory for Precise mining of Intergrown Energy and resources China University of Mining and Technology-BeijingBeijing 100083China School of Energy&mining engineering China University of Mining and Technology-BeijingBeijing 100083China State Key Laboratory of Coal resources and Safe mining China University of Mining and Technology-BeijingBeijing 100083China

Heat transfer and temperature evolution in overburden fracture and ground fissures are one of the essential topics for the identification of ground fissures via unmanned aerial vehicle(UAV) infrared imager. In this study, discrete element software UDEC was employed to investigate the overburden fracture field under different mining conditions. Multiphysics software COMSOL were employed to investigate heat transfer and temperature evolution of overburden fracture and ground fissures under the influence of mining condition, fissure depth, fissure width, and month alternation. The UAV infrared field measurements also provided a calibration for numerical simulation. The results showed that for ground fissures connected to underground goaf(Fissure Ⅰ), the temperature difference increased with larger mining height and shallow buried depth. In addition, Fissure Ⅰ located in the boundary of the goaf have a greater temperature difference and is easier to be identified than fissures located above the mining goaf. For ground fissures having no connection to underground goaf(Fissure Ⅱ), the heat transfer is affected by the internal resistance of the overlying strata fracture when the depth of Fissure Ⅱ is greater than10 m, the temperature of Fissure Ⅱ gradually equals to the ground temperature as the fissures’ depth increases, and the fissures are difficult to be identified. The identification effect is most obvious for fissures larger than 16 cm under the same depth. In spring and summer, UAV infrared identification of mining fissures should be carried out during nighttime. This study provides the basis for the optimal time and season for the UAV infrared identification of different types of mining ground fissures.

关键词： Heat transfer Overburden fracture Ground fissures Infrared thermal imaging Unmanned aerial vehicle(UAV) COMSOL simulation

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Synergistic strengthening mechanism of Ca^(2+)-sodium silicate to selective separation of feldspar and quartz

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International Journal of Minerals,Metallurgy and Materials 2024年第9期31卷 1985-1995页

作者： Bo Lin Jingzhong Kuang Yiqiang Yang Zheyu Huang Delong Yang Mingming Yu School of resources and Environmental engineering Jiangxi University of Science and TechnologyGanzhou 341000China Jiangxi Key Laboratory of mining engineering Ganzhou 341000China

Inhibitors are important for flotation separation of quartz and *** this study,a novel combined inhibitor was used to separate quartz and feldspar in near-neutral *** inhibition of the combined inhibitor was assessed by micro-flotation *** a series of detection methods were used to detect differences in the surface properties of feldspars and quartz after flotation reagents and put forward the synergistic strengthening *** outcomes were pointed out that pre-mixing combined inhibitors were more effective than the addition of Ca^(2+)and SS in sequence under the optimal proportion of 1:5.A concentrate from artificial mixed minerals that was characterized by a high quartz grade and a high recovery was acquired,and was found to be 90.70wt% and 83.70%,*** was demonstrated that the combined inhibitor selectively prevented the action of the collector and feldspar from Fourier-transform infrared(FT-IR)and adsorption capacity *** results of X-ray photoelectron spectroscopy(XPS)indicated that Ca^(2+)directly interacts with the surface of quartz to increase the adsorption of *** contrast,the chemistry property of Al on the feldspar surface was altered by combined inhibitor due to Na^(+)and Ca^(2+)taking the place of K^(+),resulting in the composite inhibitor forms a hydrophilic structure,which prevents the adsorption of the collector on the surface of feldspar by interacting with the Al active *** combination of Ca^(2+)and SS synergically strengthens the difference of collecting property between quartz and feldspar by collector,thus achieving the effect of efficient separation.A new strategy for flotation to separate quartz from feldspar in near-neutral pulp was provided.

关键词： feldspar quartz Ca^(2+)-sodium silicate selective adsorption flotation separation

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Pore-pressure and stress-coupled creep behavior in deep coal:Insights from real-time NMR analysis

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International Journal of mining Science and Technology 2024年第1期34卷 77-90页

作者： Wenhao Jia Hongwei Zhou Senlin Xie Yimeng Wang Xinfeng Hu Lei Zhang School of Mechanics and Civil engineering China University of Mining and Technology-BeijingBeijing 100083China School of Energy and mining engineering China University of Mining and Technology-BeijingBeijing 100083China State Key Laboratory of Coal resources and Safe mining China University of Mining and Technology-BeijingBeijing 100083China College of Safety and Emergency Management engineering Taiyuan University of TechnologyTaiyuan 030024China

Understanding the variations in microscopic pore-fracture structures(MPFS) during coal creep under pore pressure and stress coupling is crucial for coal mining and effective gas treatment. In this manuscript, a triaxial creep test on deep coal at various pore pressures using a test system that combines in-situ mechanical loading with real-time nuclear magnetic resonance(NMR) detection was ***-scale quantitative characterization, online real-time detection, and visualization of MPFS during coal creep influenced by pore pressure and stress coupling were performed using NMR and NMR imaging(NMRI) techniques. The results revealed that seepage pores and microfractures(SPM) undergo the most significant changes during coal creep, with creep failure gradually expanding from dense primary pore fractures. Pore pressure presence promotes MPFS development primarily by inhibiting SPM compression and encouraging adsorption pores(AP) to evolve into SPM. Coal enters the accelerated creep stage earlier at lower stress levels, resulting in more pronounced creep deformation. The connection between the micro and macro values was established, demonstrating that increased porosity at different pore pressures leads to a negative exponential decay of the viscosity coefficient. The Newton dashpot in the ideal viscoplastic body and the Burgers model was improved using NMR experimental results, and a creep model that considers pore pressure and stress coupling using variable-order fractional operators was developed. The model’s reasonableness was confirmed using creep experimental data. The damagestate adjustment factors ω and β were identified through a parameter sensitivity analysis to characterize the effect of pore pressure and stress coupling on the creep damage characteristics(size and degree of difficulty) of coal.

关键词： Real-time monitoring Pore pressure-stress coupling Microscopic pore-fracture structure Variable-order fractional creep model Deep coal

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Influence and optimization of swirler parameters on elbow wear of deep coal fluidization pipeline transportation system

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Friction 2024年第7期12卷 1408-1433页

作者： Shaodi ZHAO Jiusheng BAO Shirong GE Zhongbin WANG Yan YIN Congguang HUANG School of Mechanical and Electrical engineering China University of Mining and TechnologyXuzhou 221116China School of Mechanical Electronic and Information engineering China University of Mining and Technology-BeijingBeijing 100083China Frontier Scientific Research Center for Fluided mining of Deep Underground resources China University of Mining and TechnologyXuzhou 221008China

Elbow wear is a major threat to the multiphase pipeline transportation industry,which has a negative impact on the stable operation of the transportation *** order to find the wear reduction methods of elbows in the fluidization pipeline transportation system for 2000-meter-deep coal resources,the swirler was installed upstream of the elbows,and wear simulations and tests of three kinds of elbows were carried *** results showed that the maximum wear rate(MWR)of elbows increased and then decreased along the elbow *** to the different directions of gravity,the heavy wear position(HWP)of the horizontal-vertical(H-V)elbow was in front of the vertical-horizontal(V-H)*** the downstream portion of the horizontal-horizontal(H-H)elbow was still a horizontal pipe,the HWP of the H-H elbow almost covered the whole *** swirler placed upstream of the elbows could make the particles at the elbow move to the intrados of the elbows,resulting in less collision between the particles and the extrados of the elbows,thus reducing the wear of the *** wear reduction effects of swirlers on three different elbows were favorably connected with the guide vane angle(GVA)and negatively correlated with the guide vane length(GVL),decreased first and then increased as the guide vane height(GVH)increased,and were little affected by the guide vane number(GVN)and the guide vane thickness(GVT).The mathematical models between the MWR of the elbows and guide vane parameters were *** bench tests,the wear reduction effect of three kinds of elbows under the optimal guide vane parameters was 58.4%,76.9%,and 78.6%,*** errors between the bench test results and the simulation results were around 10%.

关键词： pipe elbow erosion wear spiral flow swirler guide vane parameters particle collision

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Study on the evolution of solid–liquid–gas in multi-scale pore methane in tectonic coal

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Chinese Journal of Chemical engineering 2024年第7期71卷 122-131页

作者： Junjie Cai Xijian Li Hao Sui Honggao Xie College of resources and Environmental engineering Guizhou UniversityGuiyang 550025China mining College Guizhou UniversityGuiyang 550025China

The rich accumulation of methane(CH_(4))in tectonic coal layers poses a significant obstacle to the safe and efficient extraction of coal seams and coalbed *** coal samples from three geologically complex regions were selected,and the main results obtained by using a variety of research tools,such as physical tests,theoretical analyses,and numerical simulations,are as follows:22.4–62.5 nm is the joint segment of pore volume,and 26.7–100.7 nm is the joint segment of pore specific surface *** the dynamic gas production process of tectonic coal pore structure,the adsorption method of methane molecules is“solid–liquid adsorption is the mainstay,and solid–gas adsorption coexists”.Methane stored in micropores with a pore size smaller than the jointed range is defined as solid-state *** within the jointed range,which transition from micropore filling to surface adsorption,are defined as gaseous *** outside the jointed range,where solid–liquid adsorption occurs,are defined as liquid *** evolution of pore structure affects the methane adsorption mode,which provides basic theoretical guidance for the development of coal seam resources.

关键词： Tectonic coal Multiscale pore structure Methane adsorption Micropore filling Monolayer Molecular simulation

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Stability mechanism and control of the pumpable supports in longwall recovery room

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International Journal of mining Science and Technology 2024年第7期34卷 957-974页

作者： Dong Zhang Jianbiao Bai Zhijun Tian Zizheng Zhang Yonghong Guo Rui Wang Ying Xu Hao Fu Shuai Yan Min Deng Shuaigang Liu State Key Laboratory of Coal resources and Safe mining China University of Mining and TechnologyXuzhou 221116China Key Laboratory of Xinjiang Coal resources Green mining Xinjiang Key Laboratory of Coal-bearing Resources Exploration and ExploitationXinjiang Engineering Research Center of Green Intelligent Coal MiningXinjiang Institute of EngineeringUrumqi 830023China Work Safety Key Laboratory on Prevention and Control of Gas and Roof Disasters for Southern Goal Mines Hunan Provincial Key Laboratory of Safe Mining Techniques of Coal MinesHunan University of Science and TechnologyXiangtan 411201China School of Mines China University of Mining and TechnologyXuzhou 221116China

The load-bearing performance(LBP)of pumpable supports(PPS)is crucial for the stability of longwall pre-driven recovery room(PRR)surrounding ***,the unbalanced bearing coefficient(UBC)of the PPS(undertaking unequal load along the mining direction)has not been investigated.A mechanical model of the PRR was established,considering the main roof cantilever beam structure,to derive an assessment formula for the load,the failure criteria,and the UBC of the ***,the generation mechanisms,and influencing factors of the UBC were *** sensitivity analysis shows that the main roof hanging length(l_(2))and the spacing between the PPS(r)significantly impact the UBC.A novel design of the PPS and the coupling control technology were proposed and applied to reduce the UBC of the PPS in the adjacent longwall *** results showed no failure of the PPS at the test site,with the UBC(ζ)reduced to 1.1 consistent with the design value(1.15)basically,fully utilizing the collaborative LBP of the ***,the maximum roof-to-floor convergence of the PRR was 234 mm,effectively controlling the stability of the surrounding rock of the PRR and ensuring the mining equipment recovery.

关键词： Pre-driven recovery room Pumpable supports Unbalanced bearing coefficient Hydraulic fracture Stability analysis Surrounding rock control

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Damage degradation mechanism and macro-meso structural response of mudstone after water wetting

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Journal of Mountain Science 2024年第8期21卷 2825-2843页

作者： SHAO Zhixin SONG Yanqi ZHENG Junjie SHEN Fuxin LIU Chuanpeng YANG Juntao School of Mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China State Key Laboratory of Coal resources and Safe mining China University of Mining&Technology(Beijing)Beijing 100083China

The predominant presence of weak interlayers primarily composed of mudstone renders them highly susceptible to a reduction in bearing capacity due to the water-rock weakening effect,significantly impacting the safety of open-pit mining *** study focuses on the weak mudstone layers within open-pit mine *** mineral composition of mudstone and the microstructure evolution characteristics before and after water wetting were analyzed by X-ray diffraction(XRD)and scanning electron microscope(SEM).The meso-structure and parameter variation characteristics of mudstone interior space after water-rock interaction were quantified by computed tomography scanning test,and the damage variable characterization method was ***,according to the uniaxial compression test,the degradation characteristics of the macroscopic mechanical behavior of mudstone under different water wetting time were explored,and the elastic modulus and strength attenuation model of mudstone based on mesoscopic damage were ***,building upon the macro-meso structural response characteristics of mudstone,an exploration of the failure characteristics and deterioration mechanism under the influence of water-rock interactions was *** results show that the water-rock interaction makes the internal defects of mudstone gradually develop and form a fracture network structure,which eventually leads to the deterioration of its macroscopic mechanical *** porosity,fractal dimension and damage characteristics of mudstone show an exponential trend with the increase of water wetting ***,the deterioration mechanism of mudstone after water wetting are postulated to encompass factors such as the hydrophilicity of mineral molecular structures,hydration stress and expansion effects on clay particles,as well as the spatial distribution of microcracks and the phenomenon of fracture *** outcomes of this research endeavor aim to provide cer

关键词： Moisture absorption of mudstone Computed tomography scanning test Fracture structure evolution Macro-meso structural response Deterioration mechanism

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Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea

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Deep Underground Science and engineering 2024年第2期3卷 197-206页

作者： Zhuangcai Tian Yihua Chang Sichao Chen Gengchen Wang Yanhong Hu Chuan Guo Lei Jia Lei Song Jianhua Yue State Key Laboratory for Geomechanics and Deep Underground engineering China University of Mining and TechnologyXuzhouChina School of Mechanics and Civil engineering China University of Mining and TechnologyXuzhouChina Research Center for Deep Ocean Science and Underwater engineering China University of Mining and TechnologyXuzhouChina School of resources and Geosciences China University of Mining and TechnologyXuzhouChina

In recent years,the exploration of seabed has been intensified,but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so *** this study,the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron *** test results suggest that the shear strength of silt and sand increases linearly with the increase of normal *** on the direct shear test,the scanning electron microscope was used to observe the section surface of *** is observed that the section surface becomes rough,with many“V”‐shaped *** particles appear on the surface of the silt structure and tend to be *** X‐ray diffraction experiment reveals that the sand and silt have different *** shear strength of sand is slightly greater than that of silt under high stress,which is related to the shape of soil particles and the mineral *** results can be a reference for further study of other soils in the Yellow Sea;meanwhile,they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.

关键词： direct shear test microscope physical properties submarine soil Yellow Sea

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Identifying the real fracture hidden in rock microcrack zone by acoustic emission energy

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International Journal of mining Science and Technology 2024年第6期34卷 731-746页

作者： Yuekun Xing Bingxiang Huang Guangqing Zhang Binghong Li Hang Xu Xuejie Jiao Yang Yu Taisen Han Jinlong Chen State Key Laboratory for Fine Exploration and Intelligent Development of Coal resources China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Petroleum resources and engineering China University of Petroleum-BeijingBeijing 102249China

Identifying the real fracture of rock hidden in acoustic emission(AE)source clusters(AE-depicted microcrack zone)remains challenging and *** we revealed the AE energy(representing dissipated energy)distribution rule in the rock microcrack zone and proposed an AE-energy-based method for identifying the real fracture.(1)A set of fracture experiments were performed on granite using wedgeloading,and the fracture process was detected and recorded by *** microcrack zone associated with the energy dissipation was characterized by AE sources and energy distribution,utilizing our selfdeveloped AE analysis program(RockAE).(2)The accumulated AE energy,an index representing energy dissipation,across the AE-depicted microcrack zone followed the normal distribution model(the mean and variance relate to the real fracture path and the microcrack zone width).This result implies that the nucleation and coalescence of massive cracks(i.e.,real fracture generation process)are supposed to follow a normal distribution.(3)Then,we obtained the real fracture extension path by joining the peak positions of the AE energy normal distribution curve at different cross-sections of the microcrack ***,we distinguished between the microcrack zone and the concealed real fracture within *** deviation was validated as slight as 1–3 mm.

关键词： GeoEnergy exploitation Rock fracture Fracture identification Acoustic emission AE energy analysis

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Failure evolution and disaster prediction of rock under uniaxial compression based on non-extensive statistical analysis of electric potential

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International Journal of mining Science and Technology 2024年第7期34卷 975-993页

作者： Tiancheng Shan Zhonghui Li Haishan Jia Enyuan Wang Xiaoran Wang Yue Niu Xin Zhang Dong Chen Shan Yin Quancong Zhang State Key Laboratory of Coal Mine Disaster Prevention and Control China University of Mining and TechnologyXuzhou 221116China National engineering Research Center for Coal Gas Control China University of Mining and TechnologyXuzhou 221116China School of Safety engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory for Fine Exploration and Intelligent Development of Coal resources China University of Mining and TechnologyXuzhou 221116China State Key Laboratory for Geomechanics and Deep Underground engineering China University of Mining and TechnologyXuzhou 221116China

Rock failure can cause serious geological disasters,and the non-extensive statistical features of electric potential(EP)are expected to provide valuable information for disaster *** this paper,the uniaxial compression experiments with EP monitoring were carried out on fine sandstone,marble and granite samples under four displacement *** Tsallis entropy q value of EPs is used to analyze the selforganization evolution of rock *** the influence of displacement rate and rock type on q value are explored by mineral structure and fracture modes.A self-organized critical prediction method with q value is *** results show that the probability density function(PDF)of EPs follows the q-Gaussian *** displacement rate is positively correlated with q *** the displacement rate increasing,the fracture mode changes,the damage degree intensifies,and the microcrack network becomes *** influence of rock type on q value is related to the burst intensity of energy release and the crack fracture *** q value of EPs can be used as an effective prediction index for rock failure like b value of acoustic emission(AE).The results provide useful reference and method for the monitoring and early warning of geological disasters.

关键词： Electric potential Non-extensive statistical feature Displacement rate q-Gaussian distribution Precursor prediction Rock materials

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