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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 conducted.Full-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

Temporal assembly patterns of microbial communities in three parallel bioreactors treating low-concentration coking wastewater with differing carbon source concentrations

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Journal of Environmental Sciences 2024年第3期137卷 455-468页

作者： Weijia Li Yu Xia Na Li Jie Chang Jing Liu Pei Wang Xuwen He school of Chemical and Environmental engineering China University of Mining and Technology-BeijingBeijing 100083China

Carbon source is an important factor of biological treatment systems, the effects of which on their temporal community assembly patterns are not sufficiently understood currently.In this study, the temporal dynamics and driving mechanisms of the communities in three parallel bioreactors for low-concentration coking wastewater(CWW) treatment with differing carbon source concentrations(S0 with no glucose addition, S1 with 200 mg/L glucose addition and S2 with 400 mg/L glucose addition) were comprehensively studied. Highthroughput sequencing and bioinformatics analyses including network analysis and Infer Community Assembly Mechanisms by Phylogenetic bin-based null model(iCAMP) were used. The communities of three systems showed turnover rates of 0.0029~0.0034 every 15days. Network analysis results showed that the S0 network showed higher positive correlation proportion(71.43%) and clustering coefficient(0.33), suggesting that carbon source shortage in S0 promoted interactions and cooperation of microbes. The neutral community model analysis showed that the immigration rate increased from 0.5247 in S0 to 0.6478in S2. The iCAMP analysis results showed that drift(45.89%) and homogeneous selection(31.68%) dominated in driving the assembly of all the investigated microbial communities.The contribution of homogeneous selection increased with the increase of carbon source concentrations, from 27.92% in S0 to 36.08% in S2. The OTUs participating in aerobic respiration and tricarboxylic acid(TCA) cycle were abundant among the bins mainly affected by deterministic processes, while those related to the metabolism of refractory organic pollutants in CWW such as alkanes, benzenes and phenols were abundant in the bins dominated by stochastic processes.

关键词： Coking wastewater treatment Temporal dynamics Network analysis Deterministic processes Stochastic processes

Transient synthesis of carbon-supported high-entropy alloy sulfide nanoparticles via flash Joule heating for efficient electrocatalytic hydrogen evolution

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Nano Research 2024年第4期17卷 3379-3389页

作者： Yuntian Liao Rongtao Zhu Wenjun Zhang Haiyang Zhu Yang Sun Jiale Chen Zhenhua Dong Ronghuan Lv school of Chemical engineering and Technology China University of Mining and TechnologyXuzhou 221116China

High entropy alloys(HEA)are frequently employed as catalysts in electrocatalytic hydrogen evolution.However,the traditional high entropy alloy synthesis methods are time-consuming,energy-intensive,and environmentally polluting,which limits their application in the hydrogen evolution reaction(HER).This study leveraged the capabilities of flash Joule heating(FJH)to synthesize carbon-supported high-entropy alloy sulfide nanoparticles(CC-S-HEA)on carbon cloth(CC)with good self-standing properties within 300 ms.The carbon thermal shock generated by the Joule heating could pyrolyze the sulfur source into gas,resulting in numerous pore structures and defects on CC,forming an S-doped carbon substrate(CC-S).Then the S atoms were used to stably anchor the metal atoms on CC-S to form high-density uniformly dispersed HEA particles.The electrochemical test results demonstrated that CC-S-HEA prepared at 60 V flash voltage had HER performance comparable to Pt/C.The density functional theory(DFT)calculation indicated that the S atoms on CC-S accelerated the electron transfer between the carbon substrate and HEA particles.Moreover,the unique electronic structure of CC-S-HEA was beneficial to H*adsorption and promoted catalytic kinetics.The simplicity and versatility of FJH synthesis are of great significance for optimizing the synthesis of HEA and improving the quality of HEA products,which provides a broad application prospect for the synthesis of nanocatalysts with efficient HER performance.

关键词： high entropy alloy flash Joule heating carbon thermal shock hydrogen evolution reaction density functional theory

The influence of inter-band rock on rib spalling in longwall panel with large mining height

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International Journal of mining Science and Technology 2024年第4期34卷 427-442页

作者： Jiachen Wang Meng Li Zhaohui Wang Zheng Li Han Zhang Shixiong Song school of Energy and mining engineering China University of Mining and Technology-BeijingBeijing 100083China Coal Industry engineering Research Center of Top-coal Caving mining Beijing 100083China Faculty of engineering Hokkaido UniversitySapporo 060-8628Japan

In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by considering the rock layer.A safety factor is defined foy the rib,and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock.A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability.It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability.The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area.The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line,which tends to provide a good stability state for the rib.For different inter-band rock positions,two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.

关键词： Rib spalling Inter-band rock Large mining height Limit analysis Physical model experiment Numerical simulation

Energy Absorption by 3D-Printed Mesh Structures with a Negative Poisson’s Ratio

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Acta Metallurgica Sinica(English Letters) 2024年第1期37卷 205-212页

作者： Wenyu Li Weiming Yang Mingze Li Xiang Zhang Ping Zhang Yucheng Zhao Peijian Chen Haishun Liu school of Mechanics and Civil engineering China University of Mining and TechnologyXuzhou221116China school of Materials Sciences and Physics China University of Mining and TechnologyXuzhou221116China

A negative Poisson's ratio(NPR)structure represents optimal impact-resistance with applications in various fields,including the crash box in vehicles,which absorbs impact kinetic energy.The crash box is designed to deform in response to impact,increasing local structural density,which enhances impact resistance performance.Current studies have only focused on the NPR effect in the plane dimension at low-speed loads.Few studies have considered high-speed impact loads on three-dimensional NPR structures.We have developed two types of AlSi10Mg alloy energy-absorbing structures with NPR using three-dimensional printing technology,and have compared our systems with a conventional hexagonal mesh structure.Sample testing involved split-Hopkinson pressure bar measurements,which showed good agreement with dynamic numerical simulations.When subjected to an impact load,the NPR structure exhibited better impact resistance and energy absorption compared with the positive Poisson's ratio structure.The proposed dual-layer hexagonal structure ensures an NPR effect while exhibiting higher strength and improved stability relative to the conventional concave hexagon structure.

关键词： Negative Poisson’s ratio Energy absorption 3D printing Split-Hopkinson pressure bar Numerical simulation

Nonlinear empirical failure criterion for rocks under triaxial compression

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International Journal of mining Science and Technology 2024年第3期34卷 351-369页

作者： Hongtao Liu Zhou Han Zijun Han Zihan Chen Qinyu Liu Hongkai Zhang Rongguang Zhang Linfeng Guo school of Energy&mining engineering China University of Mining and Technology-BeijingBeijing 100083China China National Coal Association Beijing 100010China

Based on existing triaxial compression experimental data,a new empirical failure criterion with wide applicability was proposed considering hydrostatic pressure,second stress invariance,and maximum shear stress.Four fitting evaluation indicators were used to verify the consistency of the new failure criterion,and the differences with the other 6 failure criteria were discussed.The characteristics of the new failure criteria in the principal stress space were finally analyzed.The results indicate that(1)the new failure criterion exhibits strong predictive ability for triaxial experiments and has good applicability for both intact and jointed rocks;(2)the influence of hydrostatic pressure on the failure surface exhibits a non-linear trend,and different hydrostatic pressure also exhibits different distribution patterns on the deviatoric stress plane,with a distribution characteristic pattern of hexagonal snowflake-regular hexagon.The maximum shear stress has a torsional effect on the new criterion,in the three-dimensional failure surface.The parameters a and b of the rock have an impact on the failure surface morphology of the new criterion function on the offset surface.

关键词： surface. criterion hydrostatic

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

Study on creep deformation and energy development of underground surrounding rock under four‐dimensional support

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Deep Underground Science and engineering 2024年第1期3卷 25-38页

作者： Zhanguo Ma Junyu Sun Peng Gong Pengfei Yan Nan Cui Ruichong Zhang school of Mechanics and Civil engineering China University of Mining and TechnologyXuzhouChina State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground engineering China University of Mining and TechnologyXuzhouChina Department of mining engineering Colorado School of MinesGoldenUSA

There is an urgent need to develop optimal solutions for deformation control of deep high‐stress roadways,one of the critical problems in underground engineering.The previously proposed four‐dimensional support(hereinafter 4D support),as a new support technology,can set the roadway surrounding rock under three‐dimensional pressure in the new balanced structure,and prevent instability of surrounding rock in underground engineering.However,the influence of roadway depth and creep deformation on the surrounding rock supported by 4D support is still unknown.This study investigated the influence of roadway depth and creep deformation time on the instability of surrounding rock by analyzing the energy development.The elastic strain energy was analyzed using the program redeveloped in FLAC3D.The numerical simulation results indicate that the combined support mode of 4D roof supports and conventional side supports is highly applicable to the stability control of surrounding rock with a roadway depth exceeding 520 m.With the increase of roadway depth,4D support can effectively restrain the area and depth of plastic deformation in the surrounding rock.Further,4D support limits the accumulation range and rate of elastic strain energy as the creep deformation time increases.4D support can effectively reduce the plastic deformation of roadway surrounding rock and maintain the stability for a long deformation period of 6 months.As confirmed by in situ monitoring results,4D support is more effective for the long‐term stability control of surrounding rock than conventional support.

关键词： coal mines elastic strain energy four‐dimensional support large roadway depth long‐term stability control plastic deformation surrounding rock

Mechanism of high-preload support based on the NPR anchor cable in layered soft rock tunnels

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Journal of Mountain Science 2024年第4期21卷 1403-1418页

作者： SUI Qiru HE Manchao SHI Mengfan TAO Zhigang ZHAO Feifei ZHANG Xiaoyu State Key Laboratory for Tunnel engineering China University of Mining and Technology(Beijing)Beijing 100083China school of Mechanics and Civil engineering China University of Mining and Technology(Beijing)Beijing 100083China

The control of large deformation problems in layered soft rock tunnels needs to solve urgently.The roof problem is particularly severe among the deformation issues in tunnels.This study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large deformations.Subsequently,we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor cables.The prominent roles of long and short NPR anchor cables in the support system are also analyzed.The results indicate the significance of high preload in controlling the roof of layered soft rock tunnels.The short NPR anchor cables effectively improve the integrity of the stratified soft rock layers,while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock layers.Finally,the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data.

关键词： Tunnel engineering Soft rock High-preload support NPR anchor cables