A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geogr...A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.展开更多
Earthquake-related hydrochemical changes in thermal springs have been widely observed;however,quantitative modeling of the reactive transport process is absent.In the present study,we apply reactive transport simulati...Earthquake-related hydrochemical changes in thermal springs have been widely observed;however,quantitative modeling of the reactive transport process is absent.In the present study,we apply reactive transport simulation to capture the hydrochemical responses in a thermal spring following the Wenchuan Ms 8.0 and Lushan Ms 7.0 earthquakes.We first constrain deep reservoir geothermal fluid compositions and temperature by multicomponent geothermometry,and then a reactive geochemical transport model is constructed to reproduce the hydrochemical evolution process.The results show that the recharge from the shallow aquifer increases gradually until it reaches a peak because of the permeability enhancement caused by the Lushan earthquake,which may be the mechanism to explain the earthquake-related hydrochemical responses.In contrast to the postseismic effect of the Wenchuan earthquake,the chemical evolution can be considered as hydrochemical anomalies related to the Lushan earthquake.This study proves that the efficient simulation of reactive transport processes is useful for investigating earthquake-related signals in hydrochemical time series.展开更多
The stability of coal walls(pillars)can be seriously undermined by diverse in-situ dynamic disturbances.Based on a 3D par-ticle model,this work strives to numerically replicate the major mechanical responses and acous...The stability of coal walls(pillars)can be seriously undermined by diverse in-situ dynamic disturbances.Based 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 parameters.Six 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 softening.The 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 b-value.The proposed numerical model succeeds in replicating the stress-strain relations of lab data as well as the elastic-after effect in DCL tests.The effect of damping on energy dissipation and phase shift in numerical model is summarized.展开更多
This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reser...This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.展开更多
The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for th...The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for the premature failure of coal dams.However,the diffusion process of harmful ions in coal is far from clear,limiting the reliability and durability of coal dam designs.This paper investigates sulfate diffusion in coal pillar through experimental and analytical methods.Coal specimens are prepared and exposed to sulfate solutions with different concentrations.The sulfate concentrations at different locations and time are measured.Based on experimental data and Fick's law,the time-dependent surface concentration of sulfate and diffusion coefficient are determined and formulated.Further,an analytical model for predicting sulfate diffusion in coal pillar is developed by considering dual time-dependent characteristics and Laplace transformations.Through comparisons with experimental data,the accuracy of the analytical model for predicting sulfate diffusion is verified.Further,sulfate diffusions in coal dams for different concentrations of sulfate in mine water are investigated.It has been found that the sulfate concen-tration of exposure surface and diffusion coefficient in coal are both time-dependent and increase with time.Conventional Fick's law is not able to predict the sulfate diffusion in coal pillar due to the dual time-dependent characteristics.The sulfate attacking makes the coal dam a typical heterogeneous gradient structure.For sulfate concentrations 0.01-0.20 mol/L in mine water,it takes almost 1.5 and 4 years for sulfate ions to diffuse 9.46 and 18.92 m,respectively.The experimental data and developed model provide a practical method for predicting sulfate diffusion in coal pillar,which helps the service life design of coal dams.展开更多
Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating...Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.展开更多
The fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions are important when evaluating the dynamic failure of coal.In this study,coupled static-dynamic loading test...The fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions are important when evaluating the dynamic failure of coal.In this study,coupled static-dynamic loading tests are conducted on Brazilian disc(BD)coal specimens using a modified split Hopkinson pressure bar(SHPB).The effects of the static axial pre-stress and loading rate on the dynamic tensile strength and crack propagation characteristics of BD coal specimens are studied.The average dynamic indirect tensile strength of coal specimens increases first and then decreases with the static axial pre-stress increasing.When no static axial pre-stress is applied,or the static axial pre-stress is 30%of the static tensile strength,the dynamic indirect tensile strength of coal specimens shows an increase trend as the loading rate increases.When the static axial pre-stress is 60%of the static tensile strength,the dynamic indirect tensile strength shows a fluctuant trend as the loading rate increases.According to the crack propagation process of coal specimens recorded by high-speed camera,the impact velocity influences the mode of crack propagation,while the static axial pre-stress influences the direction of crack propagation.The failure of coal specimens is a coupled tensile-shear failure under high impact velocity.When there is no static axial pre-stress,tensile cracks occur in the vertical loading direction.When the static axial pre-stress is applied,the number of cracks perpendicular to the loading direction decreases,and more cracks occur in the parallel loading direction.展开更多
Aeolian sandy soil in mining areas exhibits intense evaporation and poor water retention capacity.This study was designed to find a suitable biochar application method to improve soil water infiltration and minimize s...Aeolian sandy soil in mining areas exhibits intense evaporation and poor water retention capacity.This study was designed to find a suitable biochar application method to improve soil water infiltration and minimize soil water evaporation for aeolian sand soil.Using the indoor soil column method,we studied the effects of three application patterns(A(0-20 cm was a mixed sample of mixed-based biochar and soil),B(0-10 cm was a mixed sample of mixed-based biochar and soil and 10-20 cm was soil),and C(0-10 cm was soil and 10-20 cm was a mixed sample of mixed-based biochar and soil)),four application amounts(0%(control,CK),1%,2%,and 4%of mixed-based biochar in dry soil),and two particle sizes(0.05-0.25 mm(S1)and<0.05 mm(S2))of mixed-based biochar on water infiltration and evaporation of aeolian sandy soil.We separately used five infiltration models(the Philip,Kostiakov,Horton,USDA-NRCS(United States Department of Agriculture-Natural Resources Conservation Service),and Kostiakov-Lewis models)to fit cumulative infiltration and time.Compared with CK,the application of mixed-based biochar significantly reduced cumulative soil water infiltration.Under application patterns A,B,and C,the higher the application amount and the finer the particle size were,the lower the migration speed of the wetting front.With the same application amount,cumulative soil water infiltration under application pattern A was the lowest.Taking infiltration for 10 min as an example,the reductions of cumulative soil water infiltration under the treatments of A2%(S2),A4%(S1),A4%(S2),A1%(S1),C2%(S1),and B1%(S1)were higher than 30%,which met the requirements of loess soil hydraulic parameters suitable for plant growth.The five infiltration models well fitted the effects of the treatments of application pattern C and S1 particle size(R2>0.980),but the R2 values of the Horton model exceeded 0.990 for all treatments(except for the treatment B2%(S2)).Compared with CK,all other treatments reduced cumulative soil water infiltration,except for B4%(S2).With the same application amount,cumulative soil water evaporation difference between application patterns A and B was small.Treatments of application pattern C and S1 particle size caused a larger reduction in cumulative soil water evaporation.The reductions in cumulative soil water evaporation under the treatments of C4%(S1),C4%(S2),C2%(S1),and C2%(S2)were over 15.00%.Therefore,applying 2%of mixed-based biochar with S1 particle size to the underlying layer(10-20 cm)could improve soil water infiltration while minimizing soil water evaporation.Moreover,application pattern was the main factor affecting soil water infiltration and evaporation.Further,there were interactions among the three influencing factors in the infiltration process(application amount×particle size with the most important interaction),while there were no interactions among them in the evaporation process.The results of this study could contribute to the rational application of mixed-based biochar in aeolian sandy soil and the resource utilization of urban and agricultural wastes in mining areas.展开更多
The crack volume strain method and acoustic emission(AE)method are used to analyze the anisotropy of the crack initiation strength,damage strength,the failure mode and the AE characteristics of coal reservoir.The resu...The crack volume strain method and acoustic emission(AE)method are used to analyze the anisotropy of the crack initiation strength,damage strength,the failure mode and the AE characteristics of coal reservoir.The results show that coal reservoirs show obvious anisotropic characteristics in compressive strength,cracking initiation strength and damage strength.The compressive strength of coal reservoirs decreases with the increase of bedding angle,but the reservoirs with bedding angles of 450 and 900 differ little in compressive strength.The crack initiation strength and damage strength decrease first and then increase with the increase of bedding angle.The crack initiation strength and damage strength are the highest,at the bedding angle of 0°,moderate at the bedding angle of 90°,and lowest at the bedding angle of 45°.When the bedding angle is 0°,the failure of the coal reservoirs is mainly steady propagation of large-scale fractures.When the bedding angle is 45°,one type of failure is caused by steady propagation of small-scale fractures,and the other type of failure is due to a sudden instability of large-scale fractures.When the bedding angle is 90°,the failure is mainly demonstrated by a sudden-instability of small-scale fractures.Compared with the cumulative count method of the AE,the cumulative energy method is more suitable for determining crack initiation strength and damage strength of coal reservoirs.展开更多
Shanxi,Shaanxi,Inner Mongolia,Ningxia,and Gansu(hereafter generally referred as "the Western Area")are major coal-producing areas in China due to rich coal resources and good mining conditions.However,the We...Shanxi,Shaanxi,Inner Mongolia,Ningxia,and Gansu(hereafter generally referred as "the Western Area")are major coal-producing areas in China due to rich coal resources and good mining conditions.However,the Western Area has a serious water shortage.The surface evaporation is huge and a great amount of mine water generated in coal mining is evaporated and lost after discharging to surface.In order to protect and utilize the water resources during large-scale coal mining in the Western Area,Shenhua Group has put forward a technological idea to store mine water in underground mined areas and successfully researched and developed the coal mine underground reservoir technology by solving the technical difficulties of water source prediction,reservoir site selection,reservoir capacity design,dam construction,safety guarantee,water quality control and so on through20 years of exploration.Now Shenhua Group has successfully established a batch of reservoir in the Shendong Mining Area,obtaining great economic and social benefits.The technology is also extended to other western mining areas,providing an effective path for harmonic mining of coal and water resources in western China.展开更多
This paper analyzed the current situation and development trends of energy consumption and carbon emissions,and the current situation and development trend of coal consumption in China.In the context of recently estab...This paper analyzed the current situation and development trends of energy consumption and carbon emissions,and the current situation and development trend of coal consumption in China.In the context of recently established carbon peak and carbon neutralization targets,this paper put forward the main problems associated with the green and low-carbon development and utilization of coal.Five key technological innovation directions in mining were proposed,including green coal development,intelligent and efficient mining,low-carbon utilization and conversion of coal,energy conservation and emission reduction,carbon capture,utilization and storage(CCUS).Focusing on the above technological innovation directions,it is suggested to carry out three basic theories,including the theory of green efficient intelligent mining,clean and low-carbon utilization and transformation of coal,and CCUS.Meanwhile,it is proposed to develop 12 key technologies,including green coal mining and ecological environment protection,efficient coal mining and intelligent mine construction,key technologies and equipment for efficient coal processing,underground coal gasification and mining,ultra-high parameter and ultra-supercritical power generation technology,intelligent and flexible coal-fired power generation technology,new power cycle coal-fired power generation technology,the development of coal-based special fuels,coal-based bulk and specialty chemicals,energy conservation and consumption reduction,large-scale and low-cost carbon capture,CO_(2) utilization and storage.Finally,necessary measures from the governmental perspective were also proposed.展开更多
Structure plane is one of the important factors affecting the stability and failure mode of rock mass engineering.Rock mass structure characterization is the basic work of rock mechanics research and the important con...Structure plane is one of the important factors affecting the stability and failure mode of rock mass engineering.Rock mass structure characterization is the basic work of rock mechanics research and the important content of numerical simulation.A new 3-dimensional rough discrete fracture network(RDFN3D)model and its modeling method based on the Weierstrass-Mandelbrot(W-M)function were presented in this paper.The RDFN3D model,which improves and unifies the modelling methods for the complex structural planes,has been realized.The influence of fractal dimension,amplitude,and surface precision on the modeling parameters of RDFN3D was discussed.The reasonable W-M parameters suitable for the roughness coefficient of JRC were proposed,and the relationship between the mathematical model and the joint characterization was established.The RDFN3D together with the smooth 3-dimensional discrete fracture network(DFN3D)models were successfully exported to the drawing exchange format,which will provide a wide application in numerous numerical simulation codes including both the continuous and discontinuous methods.The numerical models were discussed using the COMSOL Multiphysics code and the 3-dimensional particle flow code,respectively.The reliability of the RDFN3D model was preliminarily discussed and analyzed.The roughness and spatial connectivity of the fracture networks have a dominant effect on the fluid flow patterns.The research results can provide a new geological model and analysis model for numerical simulation and engineering analysis of jointed rock mass.展开更多
Membrane distillation(MD)is a promising membrane separation technique used to treat industrial wastewater.When coupled with cheap heat sources,MD has significant economic advantages.Therefore,MD can be combined with s...Membrane distillation(MD)is a promising membrane separation technique used to treat industrial wastewater.When coupled with cheap heat sources,MD has significant economic advantages.Therefore,MD can be combined with solar energy to realize the large-scale and low-cost treatment of highly mineralized mine water in the western coalproducing region of China.In this study,highly mineralized mine water from the Ningdong area of China was subjected to vacuum MD(VMD)using polyvinylidene fluoride hollow-fiber membranes.The optimal operation parameters of VMD were determined by response surface optimization.Subsequently,the feasibility of VMD for treating highly mineralized mine water was explored.The fouling behavior observed during VMD was further investigated by scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM-EDS).Under the optimal parameters(pressure=-0.08 MPa,temperature=70℃,and feed flow rate=1.5 L/min),the maximum membrane flux was 8.85 kg/(m^(2) h),and the desalination rate was 99.7%.Membrane fouling could be divided into three stages:membrane wetting,crystallization,and fouling layer formation.Physical cleaning restored the flux and salt rejection rate to 94%and 97%of the initial values,respectively;however,the cleaning interval and cleaning efficiency decreased as the VMD run time increased.SEM-EDS analysis revealed that the reduction in flux was caused by the precipitation of CaCO_(3).The findings also demonstrated that the membrane wetting could be attributed to the formation of NaCl on the cross section and outer surface of the membrane.Overall,the results confirm the feasibility of MD for treating mine water and provide meaningful guidance for the industrial application of MD.展开更多
The current study investigated the impact of coal mining on deep soil moisture from the perspective of the absolute value of soil moisture.A combined classical statistics and multi-dimensional geo-statistics approach ...The current study investigated the impact of coal mining on deep soil moisture from the perspective of the absolute value of soil moisture.A combined classical statistics and multi-dimensional geo-statistics approach was employed to analyze the temporal and spatial changes in soil moisture from 0 to 10 m in the mining face of the Nalin River No.2 Mine in Northwest China from the perspective of spatial variability.The results of the study show that compared with the control area,the average value of soil moisture in 1-and 2-year subsidence areas decreased by 1.18%and 0.96%,respectively,whereas the coefcient of variation increased by 17.92%and 3.63%,respectively.Interpolation of soil moisture spatial distribution results showed that the spatial variability of soil moisture in the control area was less than that in the subsidence areas,and the spatial variability of soil moisture in the 2-year subsidence area was less than that in the 1-year subsidence area,indicating that mining increases the spatial variability of soil moisture and that the degree of spatial variability of soil moisture decreases as the subsidence enters the stable period.These results provide evidence for the mechanism by which coal mining subsidence afects soil moisture.Preferential fow caused by surface cracks,soil texture,the soil pore microstructure,and other factors in the coal mining subsidence area are the primary drivers of the increase in spatial variability of soil moisture.展开更多
Injecting carbon dioxide CO_(2)into a coal seam is an important way to improve coalbed methane recovery and to store geological carbon.The fracture mechanical characteristics of bituminous coal determine the propagati...Injecting carbon dioxide CO_(2)into a coal seam is an important way to improve coalbed methane recovery and to store geological carbon.The fracture mechanical characteristics of bituminous coal determine the propagation and evolution of cracks,which directly affect CO_(2)storage in coal seams and the efficiency of resource recovery.This study applied CO_(2)adsorption and three-point bending fracture experiments using bituminous coal samples in a gaseous state(4 MPa),subcritical state(6 MPa),and supercritical state(8 and 12 MPa)to investigate the influence of CO_(2)state and anisotropy on the fracture-related mechanical response of bituminous coal.The results show that the change in mechanical properties caused by CO_(2)adsorption is CO_(2)state-dependent.The supercritical CO_(2)adsorption at 8 MPa causes the largest decrease in the mode-I fracture toughness(KIC),which is 63.6%lower than the toughness before CO_(2)adsorption.The instability characteristics of bituminous coal show the transformation trend of“sudden-gradual-sudden fracture”.With or without CO_(2)adsorption,the order of the KIC associated with three types of bituminous coal specimens is crack-divider type>crack-arrester type>crack-short transverse type.Phenomenologically,the fracture toughness of bituminous coal is positively correlated with its specific surface area and total pore volume;the toughness is negatively correlated with its average pore size.展开更多
基金funded by State Key Laboratory of Strata Intelligent Control and Green Mining Cofounded by Shandong Province and the Ministry of Science and Technology,Shandong University of Science and Technology(Grant No.MDPC2023ZR01)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(Grant No.WPUKFJJ2019-19)Major research project of Guizhou Provincial Department of Education on innovative groups(Grant No.Qianjiaohe KY[2019]070)。
文摘A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.
基金supported by the National Key R&D Program of China(Grant No.2023YFC3209700)the National Natural Science Foundation of China(Grant Nos.41807194,41902263,41807208).
文摘Earthquake-related hydrochemical changes in thermal springs have been widely observed;however,quantitative modeling of the reactive transport process is absent.In the present study,we apply reactive transport simulation to capture the hydrochemical responses in a thermal spring following the Wenchuan Ms 8.0 and Lushan Ms 7.0 earthquakes.We first constrain deep reservoir geothermal fluid compositions and temperature by multicomponent geothermometry,and then a reactive geochemical transport model is constructed to reproduce the hydrochemical evolution process.The results show that the recharge from the shallow aquifer increases gradually until it reaches a peak because of the permeability enhancement caused by the Lushan earthquake,which may be the mechanism to explain the earthquake-related hydrochemical responses.In contrast to the postseismic effect of the Wenchuan earthquake,the chemical evolution can be considered as hydrochemical anomalies related to the Lushan earthquake.This study proves that the efficient simulation of reactive transport processes is useful for investigating earthquake-related signals in hydrochemical time series.
基金funded by Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (GJNY-20-113-03),SHGF-16-19the Fundamental Research Funds for the Central Universities (06500182)+2 种基金Funds from Joint National-Local Engineering Research Center for Safe and Precise Coal Mining (EC2021004)Funds from State Key Laboratory of Coal Resources in Western China (SKLCRKF20-07)Funds from Humboldt Research Fellowship,Funds from NSFC (52204086).
文摘The stability of coal walls(pillars)can be seriously undermined by diverse in-situ dynamic disturbances.Based 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 parameters.Six 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 softening.The 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 b-value.The proposed numerical model succeeds in replicating the stress-strain relations of lab data as well as the elastic-after effect in DCL tests.The effect of damping on energy dissipation and phase shift in numerical model is summarized.
基金This work was co-supported by the Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing(2019QN08)National Key Research and Development Program of China(2018YFC0406404)+2 种基金Research on Ecological Restoration and Protection of Coal Base in Arid Eco-fragile Region(GJNY2030XDXM-19-03.2)the Fundamental Research Funds for the Central Universities(2020YJSHH12)the scientific and technological innovation project of Shenhua Group(SHJT-16-28).
文摘This paper presents results of an experimental study to characterize the law of mineral change of fallen rock in coal mine groundwater reservoir ant its influence on water quality.The minerals of the underground reservoir of Daliuta Coal Mine is taken as the research object.Simulation experiments were designed and conducted to simulate water–rock action in the laboratory.The mineral composition was analyzed by X-ray diffractometer(XRD),the surface morphology of the mineral was analyzed by scanning electron microscope(SEM),and the specific surface area,total pore volume and average pore diameter of the mineral were measured by fast specific surface/pore analyzer(BET).The experimental results show that the sandstone and mudstone in the groundwater reservoir of Daliuta Coal Mine account for 70%and 30%,respectively.The pore diameter is 15.62–17.55 nm,and pore volume is 0.035 cc/g.Its pore structure is a key factor in the occurrence of water–rock interaction.According to the water–rock simulation experiment,the quartz content before the water–rock action is about 34.28%,the albite is about 21.84%,the feldspar is about 17.48%,and the kaolinite is about 8.00%.After the water–rock action,they are 36.14%,17.78%,11.62%,and 16.75%,respectively.The content of albite and orthoclase is reduced while the content of kaolinite is increased,that is,the Na+content becomes higher,and the Ca2+and Mg2+contents become lower.This research builds a good theoretical foundation for revealing the role of water and rock in underground coal reservoirs.
基金supported by Hunan Provincial Education Department Funded Research Projects (Grant No.22C0221)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (Grant No.GJNY-18-73.11).
文摘The stability of coal pillar dams is crucial for the long-term service of underground reservoirs storing water or heat.Chemi-cal damage of coal dams induced by ions-atttacking in coal is one of the main reasons for the premature failure of coal dams.However,the diffusion process of harmful ions in coal is far from clear,limiting the reliability and durability of coal dam designs.This paper investigates sulfate diffusion in coal pillar through experimental and analytical methods.Coal specimens are prepared and exposed to sulfate solutions with different concentrations.The sulfate concentrations at different locations and time are measured.Based on experimental data and Fick's law,the time-dependent surface concentration of sulfate and diffusion coefficient are determined and formulated.Further,an analytical model for predicting sulfate diffusion in coal pillar is developed by considering dual time-dependent characteristics and Laplace transformations.Through comparisons with experimental data,the accuracy of the analytical model for predicting sulfate diffusion is verified.Further,sulfate diffusions in coal dams for different concentrations of sulfate in mine water are investigated.It has been found that the sulfate concen-tration of exposure surface and diffusion coefficient in coal are both time-dependent and increase with time.Conventional Fick's law is not able to predict the sulfate diffusion in coal pillar due to the dual time-dependent characteristics.The sulfate attacking makes the coal dam a typical heterogeneous gradient structure.For sulfate concentrations 0.01-0.20 mol/L in mine water,it takes almost 1.5 and 4 years for sulfate ions to diffuse 9.46 and 18.92 m,respectively.The experimental data and developed model provide a practical method for predicting sulfate diffusion in coal pillar,which helps the service life design of coal dams.
基金financially supported by the Natural Science Foundation of China (No.41802192)the National Science and Technology Key Special Project of China (No.2016ZX05044-002 and No.2016ZX05043)+2 种基金the Shanxi Provincial Basic Research Program-Coal Bed Methane Joint Research Foundation (No.2012012001 and No.2015012014)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining (No.SHJT-17-42.18)the Fundamental Research Funds for the Central Universities (No.CUGL170811)
文摘Coalbed methane(CBM) resources in No.15 coal seam of Taiyuan Formation account for 55% of the total CBM resources in southern Qinshui Basin(SQB), and have a great production potential. This study aims at investigating the CBM production in No.15 coal seam and its influence factors. Based on a series of laboratory experiments and latest exploration and development data from local coal mines and CBM companies, the spatial characteristics of gas production of No.15 coal seam were analyzed and then the influences of seven factors on the gas productivity of this coal seam were discussed, including coal thickness, burial depth, gas content, ratio of critical desorption pressure to original coal reservoir pressure(RCPOP), porosity, permeability, and hydrogeological condition. The influences of hydrological condition on CBM production were analyzed based on the discussions of four aspects: hydrogeochemistry, roof lithology and its distribution, hydrodynamic field of groundwater, and recharge rate of groundwater. Finally, a three-level analytic hierarchy process(AHP) evaluation model was proposed for predicting the CBM potentials of the No.15 coal seam in the SQB. The best prospective target area for CBM production of the No.15 coal seam is predicted to be in the districts of Panzhuang, Chengzhuang and south of Hudi.
基金supported by the National Natural Science Foundation of China(No.51804309)the Yue Qi Young Scholar Project(2019QN02)+5 种基金Distinguished Scholar Project(2017JCB02)from China University of Mining and Technology-Beijing,Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(Grant No.SHJT-17-42.10)National Natural Science Foundation of China(No.U1910206)the fund of Beijing Outstanding Young Scientist Program(BJJWZYJH01201911413037)the State Key Laboratory of Coal Resources and Safe Mining(Nos.SKLCRSM16KFB07,SKLCRSM16DCB01 and SKLCRSM17DC11)Young Elite Scientists Sponsorship Program by CAST(2017QNRC001)the key project of Key Laboratory of Coal Mine Safety and High Efficiency Mining Co-established by the Province and the Ministry(Anhui University of Science and Technology)(No.JYBSYS2018201).
文摘The fracture behaviour and crack propagation features of coal under coupled static-dynamic loading conditions are important when evaluating the dynamic failure of coal.In this study,coupled static-dynamic loading tests are conducted on Brazilian disc(BD)coal specimens using a modified split Hopkinson pressure bar(SHPB).The effects of the static axial pre-stress and loading rate on the dynamic tensile strength and crack propagation characteristics of BD coal specimens are studied.The average dynamic indirect tensile strength of coal specimens increases first and then decreases with the static axial pre-stress increasing.When no static axial pre-stress is applied,or the static axial pre-stress is 30%of the static tensile strength,the dynamic indirect tensile strength of coal specimens shows an increase trend as the loading rate increases.When the static axial pre-stress is 60%of the static tensile strength,the dynamic indirect tensile strength shows a fluctuant trend as the loading rate increases.According to the crack propagation process of coal specimens recorded by high-speed camera,the impact velocity influences the mode of crack propagation,while the static axial pre-stress influences the direction of crack propagation.The failure of coal specimens is a coupled tensile-shear failure under high impact velocity.When there is no static axial pre-stress,tensile cracks occur in the vertical loading direction.When the static axial pre-stress is applied,the number of cracks perpendicular to the loading direction decreases,and more cracks occur in the parallel loading direction.
基金supported by the State Key Laboratory of Water Resource Protection and Utilization in Coal Mining,Open Foundation Ecological Self-Repair Mechanism and Promotion Technology in Shendong Mining Area,China(GJNY-18-73.19)the National Key Research and Development Program of China(2020YFC1806502)。
文摘Aeolian sandy soil in mining areas exhibits intense evaporation and poor water retention capacity.This study was designed to find a suitable biochar application method to improve soil water infiltration and minimize soil water evaporation for aeolian sand soil.Using the indoor soil column method,we studied the effects of three application patterns(A(0-20 cm was a mixed sample of mixed-based biochar and soil),B(0-10 cm was a mixed sample of mixed-based biochar and soil and 10-20 cm was soil),and C(0-10 cm was soil and 10-20 cm was a mixed sample of mixed-based biochar and soil)),four application amounts(0%(control,CK),1%,2%,and 4%of mixed-based biochar in dry soil),and two particle sizes(0.05-0.25 mm(S1)and<0.05 mm(S2))of mixed-based biochar on water infiltration and evaporation of aeolian sandy soil.We separately used five infiltration models(the Philip,Kostiakov,Horton,USDA-NRCS(United States Department of Agriculture-Natural Resources Conservation Service),and Kostiakov-Lewis models)to fit cumulative infiltration and time.Compared with CK,the application of mixed-based biochar significantly reduced cumulative soil water infiltration.Under application patterns A,B,and C,the higher the application amount and the finer the particle size were,the lower the migration speed of the wetting front.With the same application amount,cumulative soil water infiltration under application pattern A was the lowest.Taking infiltration for 10 min as an example,the reductions of cumulative soil water infiltration under the treatments of A2%(S2),A4%(S1),A4%(S2),A1%(S1),C2%(S1),and B1%(S1)were higher than 30%,which met the requirements of loess soil hydraulic parameters suitable for plant growth.The five infiltration models well fitted the effects of the treatments of application pattern C and S1 particle size(R2>0.980),but the R2 values of the Horton model exceeded 0.990 for all treatments(except for the treatment B2%(S2)).Compared with CK,all other treatments reduced cumulative soil water infiltration,except for B4%(S2).With the same application amount,cumulative soil water evaporation difference between application patterns A and B was small.Treatments of application pattern C and S1 particle size caused a larger reduction in cumulative soil water evaporation.The reductions in cumulative soil water evaporation under the treatments of C4%(S1),C4%(S2),C2%(S1),and C2%(S2)were over 15.00%.Therefore,applying 2%of mixed-based biochar with S1 particle size to the underlying layer(10-20 cm)could improve soil water infiltration while minimizing soil water evaporation.Moreover,application pattern was the main factor affecting soil water infiltration and evaporation.Further,there were interactions among the three influencing factors in the infiltration process(application amount×particle size with the most important interaction),while there were no interactions among them in the evaporation process.The results of this study could contribute to the rational application of mixed-based biochar in aeolian sandy soil and the resource utilization of urban and agricultural wastes in mining areas.
基金Supported by the National Natural Science Foundation of China(51804309,51861145403)State Key Laboratory of Water Resource Protection and Utilization in Coal Mining,China(SHJT-17-42.10)。
文摘The crack volume strain method and acoustic emission(AE)method are used to analyze the anisotropy of the crack initiation strength,damage strength,the failure mode and the AE characteristics of coal reservoir.The results show that coal reservoirs show obvious anisotropic characteristics in compressive strength,cracking initiation strength and damage strength.The compressive strength of coal reservoirs decreases with the increase of bedding angle,but the reservoirs with bedding angles of 450 and 900 differ little in compressive strength.The crack initiation strength and damage strength decrease first and then increase with the increase of bedding angle.The crack initiation strength and damage strength are the highest,at the bedding angle of 0°,moderate at the bedding angle of 90°,and lowest at the bedding angle of 45°.When the bedding angle is 0°,the failure of the coal reservoirs is mainly steady propagation of large-scale fractures.When the bedding angle is 45°,one type of failure is caused by steady propagation of small-scale fractures,and the other type of failure is due to a sudden instability of large-scale fractures.When the bedding angle is 90°,the failure is mainly demonstrated by a sudden-instability of small-scale fractures.Compared with the cumulative count method of the AE,the cumulative energy method is more suitable for determining crack initiation strength and damage strength of coal reservoirs.
文摘Shanxi,Shaanxi,Inner Mongolia,Ningxia,and Gansu(hereafter generally referred as "the Western Area")are major coal-producing areas in China due to rich coal resources and good mining conditions.However,the Western Area has a serious water shortage.The surface evaporation is huge and a great amount of mine water generated in coal mining is evaporated and lost after discharging to surface.In order to protect and utilize the water resources during large-scale coal mining in the Western Area,Shenhua Group has put forward a technological idea to store mine water in underground mined areas and successfully researched and developed the coal mine underground reservoir technology by solving the technical difficulties of water source prediction,reservoir site selection,reservoir capacity design,dam construction,safety guarantee,water quality control and so on through20 years of exploration.Now Shenhua Group has successfully established a batch of reservoir in the Shendong Mining Area,obtaining great economic and social benefits.The technology is also extended to other western mining areas,providing an effective path for harmonic mining of coal and water resources in western China.
文摘This paper analyzed the current situation and development trends of energy consumption and carbon emissions,and the current situation and development trend of coal consumption in China.In the context of recently established carbon peak and carbon neutralization targets,this paper put forward the main problems associated with the green and low-carbon development and utilization of coal.Five key technological innovation directions in mining were proposed,including green coal development,intelligent and efficient mining,low-carbon utilization and conversion of coal,energy conservation and emission reduction,carbon capture,utilization and storage(CCUS).Focusing on the above technological innovation directions,it is suggested to carry out three basic theories,including the theory of green efficient intelligent mining,clean and low-carbon utilization and transformation of coal,and CCUS.Meanwhile,it is proposed to develop 12 key technologies,including green coal mining and ecological environment protection,efficient coal mining and intelligent mine construction,key technologies and equipment for efficient coal processing,underground coal gasification and mining,ultra-high parameter and ultra-supercritical power generation technology,intelligent and flexible coal-fired power generation technology,new power cycle coal-fired power generation technology,the development of coal-based special fuels,coal-based bulk and specialty chemicals,energy conservation and consumption reduction,large-scale and low-cost carbon capture,CO_(2) utilization and storage.Finally,necessary measures from the governmental perspective were also proposed.
基金This work was financially supported by the National Key R&D Program of China(No.2021YFC2900500)the National Natural Science Foundation of China(Nos.52074020 and 42202306)+2 种基金the Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(No.WPUKFJJ2019-06)the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(No.FRF-IDRY-21001)the Natural Science Foundation of Jiangsu Province,China(No.BK20200993).
文摘Structure plane is one of the important factors affecting the stability and failure mode of rock mass engineering.Rock mass structure characterization is the basic work of rock mechanics research and the important content of numerical simulation.A new 3-dimensional rough discrete fracture network(RDFN3D)model and its modeling method based on the Weierstrass-Mandelbrot(W-M)function were presented in this paper.The RDFN3D model,which improves and unifies the modelling methods for the complex structural planes,has been realized.The influence of fractal dimension,amplitude,and surface precision on the modeling parameters of RDFN3D was discussed.The reasonable W-M parameters suitable for the roughness coefficient of JRC were proposed,and the relationship between the mathematical model and the joint characterization was established.The RDFN3D together with the smooth 3-dimensional discrete fracture network(DFN3D)models were successfully exported to the drawing exchange format,which will provide a wide application in numerous numerical simulation codes including both the continuous and discontinuous methods.The numerical models were discussed using the COMSOL Multiphysics code and the 3-dimensional particle flow code,respectively.The reliability of the RDFN3D model was preliminarily discussed and analyzed.The roughness and spatial connectivity of the fracture networks have a dominant effect on the fluid flow patterns.The research results can provide a new geological model and analysis model for numerical simulation and engineering analysis of jointed rock mass.
基金This research was supported by the Open Fund Project of the State Key Laboratory of Water Resources Protection and Utilization in Coal Mining(GJNY-18-73.13).
文摘Membrane distillation(MD)is a promising membrane separation technique used to treat industrial wastewater.When coupled with cheap heat sources,MD has significant economic advantages.Therefore,MD can be combined with solar energy to realize the large-scale and low-cost treatment of highly mineralized mine water in the western coalproducing region of China.In this study,highly mineralized mine water from the Ningdong area of China was subjected to vacuum MD(VMD)using polyvinylidene fluoride hollow-fiber membranes.The optimal operation parameters of VMD were determined by response surface optimization.Subsequently,the feasibility of VMD for treating highly mineralized mine water was explored.The fouling behavior observed during VMD was further investigated by scanning electron microscopy with energy-dispersive X-ray spectroscopy(SEM-EDS).Under the optimal parameters(pressure=-0.08 MPa,temperature=70℃,and feed flow rate=1.5 L/min),the maximum membrane flux was 8.85 kg/(m^(2) h),and the desalination rate was 99.7%.Membrane fouling could be divided into three stages:membrane wetting,crystallization,and fouling layer formation.Physical cleaning restored the flux and salt rejection rate to 94%and 97%of the initial values,respectively;however,the cleaning interval and cleaning efficiency decreased as the VMD run time increased.SEM-EDS analysis revealed that the reduction in flux was caused by the precipitation of CaCO_(3).The findings also demonstrated that the membrane wetting could be attributed to the formation of NaCl on the cross section and outer surface of the membrane.Overall,the results confirm the feasibility of MD for treating mine water and provide meaningful guidance for the industrial application of MD.
基金funded by the National Natural Science Foundation of China(42177037,52004012)Yue Qi Young Scholar Project,China University of Mining&Technology,Beijing(2019QN08)+1 种基金the Research on Ecological Restoration and Protection of Coal Base in Arid Eco-fragile Regions(GJNY2030XDXM-19-03.2)Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(GJNY-18-73.19).
文摘The current study investigated the impact of coal mining on deep soil moisture from the perspective of the absolute value of soil moisture.A combined classical statistics and multi-dimensional geo-statistics approach was employed to analyze the temporal and spatial changes in soil moisture from 0 to 10 m in the mining face of the Nalin River No.2 Mine in Northwest China from the perspective of spatial variability.The results of the study show that compared with the control area,the average value of soil moisture in 1-and 2-year subsidence areas decreased by 1.18%and 0.96%,respectively,whereas the coefcient of variation increased by 17.92%and 3.63%,respectively.Interpolation of soil moisture spatial distribution results showed that the spatial variability of soil moisture in the control area was less than that in the subsidence areas,and the spatial variability of soil moisture in the 2-year subsidence area was less than that in the 1-year subsidence area,indicating that mining increases the spatial variability of soil moisture and that the degree of spatial variability of soil moisture decreases as the subsidence enters the stable period.These results provide evidence for the mechanism by which coal mining subsidence afects soil moisture.Preferential fow caused by surface cracks,soil texture,the soil pore microstructure,and other factors in the coal mining subsidence area are the primary drivers of the increase in spatial variability of soil moisture.
基金Youth Program of National Natural Science Foundation of China(Grant No.51904195)the School Fund of Taiyuan University of Technology and Science(No.20182008).
文摘Injecting carbon dioxide CO_(2)into a coal seam is an important way to improve coalbed methane recovery and to store geological carbon.The fracture mechanical characteristics of bituminous coal determine the propagation and evolution of cracks,which directly affect CO_(2)storage in coal seams and the efficiency of resource recovery.This study applied CO_(2)adsorption and three-point bending fracture experiments using bituminous coal samples in a gaseous state(4 MPa),subcritical state(6 MPa),and supercritical state(8 and 12 MPa)to investigate the influence of CO_(2)state and anisotropy on the fracture-related mechanical response of bituminous coal.The results show that the change in mechanical properties caused by CO_(2)adsorption is CO_(2)state-dependent.The supercritical CO_(2)adsorption at 8 MPa causes the largest decrease in the mode-I fracture toughness(KIC),which is 63.6%lower than the toughness before CO_(2)adsorption.The instability characteristics of bituminous coal show the transformation trend of“sudden-gradual-sudden fracture”.With or without CO_(2)adsorption,the order of the KIC associated with three types of bituminous coal specimens is crack-divider type>crack-arrester type>crack-short transverse type.Phenomenologically,the fracture toughness of bituminous coal is positively correlated with its specific surface area and total pore volume;the toughness is negatively correlated with its average pore size.
基金Project(52009131) supported by the National Natural Science Foundation of ChinaProject(GJNY-20-113-05) supported by the Open Funds of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining,ChinaProject(2020RGET03) supported by the Fundamental Science on Radioactive Geology and Exploration Technology LaboratoryEast China University of Technology,China。
基金Project(2021YFC2900500)supported by the National Key R&D Program of ChinaProject(52074020)supported by the National Natural Science Foundation of China+1 种基金Project(WPUKFJJ2019-06)supported by the Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining,ChinaProject(FRF-IDRY-21-001)supported by the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)。
基金Project(2018YFC0604703)supported by the National Key R&D Program of ChinaProjects(51804181,51874190)supported by the National Natural Science Foundation of China+3 种基金Project(ZR2018QEE002)supported by the Shandong Province Natural Science Fund,ChinaProject(ZR2018ZA0603)supported by the Major Program of Shandong Province Natural Science Foundation,ChinaProject(2019GSF116003)supported by the Key R&D Project of Shandong Province,ChinaProject(SDKDYC190234)supported by the Shandong University of Science and Technology,Graduate Student Technology Innovation Project,China。
