A complex substrate consisting of fly ash,coal gangue and excess sludge was used as an experimental soil in pot culture experiments.Different soil compositions were tested by observing the growth of arbuscular mycorrh...A complex substrate consisting of fly ash,coal gangue and excess sludge was used as an experimental soil in pot culture experiments.Different soil compositions were tested by observing the growth of arbuscular mycorrhizal(AM) fungi inoculated white clover,rye grass or corn.The biomass of the host plants,the mycorrhizal colonization(MC) rate and the mycorrhizal dependency(MD) were measured.The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines.We used two inoculation methods:single-inoculation with Glomus versiforme or Glomus mosseae and a dual inoculation with both G.v and G.m.The results show that G.m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines.White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines.The best weight ratio of fly ash,coal gangue and excess sludge was found to be 20:60:20.The optimum treatment conditions of AMF-plant-activated-substrate are described.展开更多
Based on the statistical data from 1975 to 1997, we forecast the growth rate of coal consuming and the quantity in coming decade with the BP neuron network in the article.
A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of D...A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.展开更多
In the past decades,the intense excavation of coal resources in China has induced a series of severe waterrelated disasters or problems,such as water burst accidents,severe groundwater depletion and contamination.All ...In the past decades,the intense excavation of coal resources in China has induced a series of severe waterrelated disasters or problems,such as water burst accidents,severe groundwater depletion and contamination.All of these problems were caused by the structural changes of roof rocks or bed rocks induced by coal excavation.The structure of collapsed roof rocks is generally classified into three zones:falling zone.展开更多
By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities ...By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.展开更多
Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mech...Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mechanical model was established under the condition of rock mechanics and geostress, and the finite element method was used to simulate the paleotectonic stress field. Based on the Griffith and Mohr-Coulomb criterion, the distribution of tectonic fractures in the Shanxi Formation during the Indosinian, Yanshanian, and Himalayan period can be predicted with the index of comprehensive rupture rate. The results show that the acting force of the Pacific Plate and the India Plate to the North China Plate formed the direction of principal stress is N-S, NW - SE, and NE - SW, respectively, in different periods in the study area. Changes in the direction and strength of the acting force led to the regional gradients of tectonic stress magnitude, which resulted in an asymmetrical distribution state of the stress conditions in different periods. It is suggested that the low-stress areas are mainly located in the fault zones and extend along the direction of the fault zones. Furthermore, the high-stress areas are located in the junction of fold belts and the binding site of multiple folds. The development of tectonic fractures was affected by the distribution of stress intensity and the tectonic position of folds and faults, which resulted in some developed areas with level I and II. There are obvious differences in the development of tectonic fractures in the fold and fault zones and the anticline and syncline structure at the same fold zones. The tectonic fractures of the Shanxi Formation during the Himalayan period are more developed than those during the Indosinian and Yanshanian period due to the superposition of the late tectonic movement to the early tectonic movement and the differences in the magnitude and direction of stress intensity.展开更多
Several previous studies have indicated that nest sanitation behavior is a general adaptation in altricial birds,with egg recog nition capacity evolvi ng as a specific response to in terspecific brood parasitism(IBP)....Several previous studies have indicated that nest sanitation behavior is a general adaptation in altricial birds,with egg recog nition capacity evolvi ng as a specific response to in terspecific brood parasitism(IBP).However,a rece nt study suggested an alternative hypothesis,con cludi ng that con specific brood parasitism(CBP)selects for egg rejection in thrushes,with IBP as a by-product.In the present study,we used a spectrophotometer to quantify egg coloration and egg mimicry and performed artificial parasitism experiments in the grey?backed thrush(Turdus hortulorum).We showed that individuals of this species rejected 100%of 12 foreign eggs,without IBP or CBP detected.In a review of previous studies,we also discuss possible explanations for the high egg rejection rate in the grey-backed thrush and suggest areas for future study.Altricial birds have evolved advaneed reproductive behavior to in crease the fitn ess of their offspring by buildi ng elaborate structures(i.e.,nests),in which they lay eggs and rear their nestlings(Hansell,2000).Bird nests not only provide a suitable place for nestling development,but also act as a concealed location for safety from predators.Furthermore,bird parents have evolved nest sanitation behavior to clean foreig n objects from their n ests,in eluding feces,eggshells,branches,and leaves,because they induce predation,facilitate microorganism growth,damage eggs,or hurt nestlings during brooding(Guigueno&Sealy,2012).Therefore,nest sanitation has evolved as a general behavior in altricial birds for distinguishing between egg-shaped and non-egg-shaped objects.展开更多
The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measure...The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.展开更多
Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stab...Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.展开更多
A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the conc...A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the concepts of rock engineering system (RES). For this purpose, six longwall panels considered in Parvadeh-I coal mine. Seven major effective parameters on FAR was selected including coal mine roof rating, gas propagation, safety factor of longwall face, ratio of joint spacing to cutting depth at longwall face, longwall face inclination, panel width, floor rock mass rating. To performance evaluation of the presented model, the relationship between the average vulnerability indexes of advance operation with FAR was determined in considered panels with coefficient of determination (R2) equal to 0.884 that indicate relatively acceptable correlation and compatibility. Investigations of the research indicated that it is possible to determine the actual operation efficiency under fair conditions by a RES-based model. The inevitable reduction of FAR for each longwall panel was determined by presented model that the difference amount between the maximum possible practical face advance rate (FARmpp) and recorded actual face advance rate (FARa) indicate the operation efficiency. Applied approach in this paper can be used to prediction of FAR in retreat longwall mining panel for same conditions that can have many benefits, including better and more accurate planning for the sales market and mine operation. Also, presented method in this paper can be applied as a useful tool to determination of actual operation efficiency for other sections and extraction methods in coal mines.展开更多
Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that disc...Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.展开更多
Background: The success of cuckoo parasitism is thought to depend largely on the extent of egg matching between cuckoo and host eggs, since poor-matching cuckoo egg would lead to more frequent egg rejection by the hos...Background: The success of cuckoo parasitism is thought to depend largely on the extent of egg matching between cuckoo and host eggs, since poor-matching cuckoo egg would lead to more frequent egg rejection by the host. In this study, we investigated how egg-spot matching between the Common Cuckoo(Cuculus canorus) and its host, the Oriental Reed Warbler(Acrocephalus orientalis) is affected by the local parasitism rate, nest availability in breeding synchronization and egg rejection.Methods: We used the paired design of parasitized and their nearest non-parasitized nests where breeding occurred simultaneously to compare egg-spot matching. The image analysis was used to compare four eggshell pattern variables, namely spot size, density, coverage on the different areas of egg surface, and the distribution on the whole egg surface. Egg recognition experiments were conducted to test the effect of egg spots on egg rejection by the host.Results: Our results show that much better matching in almost all spot parameters tested on the side of the egg and the spot distribution on the whole egg occurred in parasitized nests than in non-parasitized nests. Matching of spot density between cuckoo and host eggs in parasitized nests increased with the synchronization between temporal availability of nests and the egg-laying period of female cuckoos. Egg recognition experiments in which the warbler eggs were deliberately painted with extra spots led to a significantly higher egg rejection rate(78.3%) than of unpainted eggs.Conclusion: Our data suggest that both the high temporal encounter rate between cuckoo and warbler nests as well as the high egg rejection ability of the host are important factors for egg-spot matching of the cuckoos.展开更多
To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.Th...To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.展开更多
The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'a...The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'an,as one of the state coal mining bases in China,has been seeing increasingly heavier pressure for the protection of water resources.This article considers Lu'an as an example and describes the ways these concerns may be alleviated.High mine-water utilization rates have effectively reduced wasting of water and,consequently,have reduced water demand.Using the top layers of the Ordavician as aquifuge barriers can prevent floor karst water inrush into the longwall face and can protect the regional Ordovician karst water resources at the same time.The strength of the overlying Quaternary clay can protect against roof collapse and has successfully preserved the Quaternary porous water resource.展开更多
Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock...Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.展开更多
The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrati...The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air.These concentrations differ in coal heating and cooling phase which was proven in the study.This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating(50–250°C)and cooling(250–35°C)phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed.The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines.Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index.In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane,ethylene,propane,propylene and acetylene,while in the cooling phase these ratios increased systemically.The effect of air(in heating phase)and nitrogen(in cooling phase)flow rate on the self-ignition index CO/CO2 was also determined.展开更多
Since mining rights of coal resources(for short MRCR) could be regarded as a multi-stage compound real option,the evaluation for MRCR can be better solved using op- tion theory than the NPV.In the former research,we d...Since mining rights of coal resources(for short MRCR) could be regarded as a multi-stage compound real option,the evaluation for MRCR can be better solved using op- tion theory than the NPV.In the former research,we developed a two-factor model of evaluating MRCR when the coal spot price and convenience yield are stochastic based on option theory.On the basis of this two-factor model,we set up a three-factor model of evaluating MRCR when the interest rate followed a stochastic process.Through a real example application,we found the model can get higher values than the two-factor model and the NPV.This is because considering the volatility of interest rate can improve the executive opportunity of MRCR.展开更多
Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires applicati...Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires application of kinetic and thermodynamic principles. This study aimed to identify the catalytic rate constant necessary for rate law involved in reaction mechanisms and activation energy reduction needed for heat transfer rate. Stoichiometric application for balanced total series of elementary reactions is solved for the concentration determination of reactants and products. Unsteady-state in three dimensional directions of thermodynamics is derived for the determination of heat transfer rate, temperatures at any position in a sphere using Gurney and Lurie chart and center temperature in a sphere by Heisler chart. Application principles of rate law and Arrhenius equation can result to thermal conductivity as a function of activation energy leading to synthetic fuel production.展开更多
Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable,but generally it is impractical due to the difficulty of gath...Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable,but generally it is impractical due to the difficulty of gathering essential input data.However,applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability.The coal mine floor rating(CMFR)system,developed by the University of New South Wales(UNSW),is a rockmass classification system that provides an indicator for the competence of floor strata.The most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor strata.In addition to the competence of the floor,depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability.In this study,CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor heave.Exploratory drill core data,overburden maps,and mine plans were utilized for the study.Additionally,qualitative data(failure/non-failure)on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods.It was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal Mine.In order to extend the applicability of the CMFR classification system,the methodology was modified.A calculation procedure of one of the CMFR classification system’s components,the horizontal stress rating(HSR),was changed and new parameters were added to the HSR.展开更多
基金Project 2007024 supported by the Environmental Science and Technology Fund of the Environmental Protection Department of Jiangsu Province
文摘A complex substrate consisting of fly ash,coal gangue and excess sludge was used as an experimental soil in pot culture experiments.Different soil compositions were tested by observing the growth of arbuscular mycorrhizal(AM) fungi inoculated white clover,rye grass or corn.The biomass of the host plants,the mycorrhizal colonization(MC) rate and the mycorrhizal dependency(MD) were measured.The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines.We used two inoculation methods:single-inoculation with Glomus versiforme or Glomus mosseae and a dual inoculation with both G.v and G.m.The results show that G.m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines.White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines.The best weight ratio of fly ash,coal gangue and excess sludge was found to be 20:60:20.The optimum treatment conditions of AMF-plant-activated-substrate are described.
文摘Based on the statistical data from 1975 to 1997, we forecast the growth rate of coal consuming and the quantity in coming decade with the BP neuron network in the article.
基金Supported by the China National Science and Technology Major Project(2017ZX05064)
文摘A desorption simulation experiment with the condition of simulated strata was designed. The experiment, under different depressurizing rates and the same fluid saturation, was conducted on the sample from 3# coal of Daning coal mine in Jincheng, Shanxi Province. The gas production rate and pressure change at both ends of the sample were studied systematically, and the mechanisms of some phenomena in the experiment were discussed. The experimental results show that, whether at fast or slow depressurizing rate, the methane adsorbed to high-rank coal can effectively desorb and the desorption efficiency can reach above 90%. There is an obvious inflection point on the gas yield curve during the desorption process and it appears after the pressure on the lump of coal reduces below the desorption pressure. The desorption of methane from high-rank coal is mainly driven by differential pressure, and high pressure difference is conducive to fast desorption. In the scenario of fast depressurization, the desorption inflection appears earlier and the gas production rate in the stage of rapid desorption is higher. It is experimentally concluded that the originally recognized strategy of long-term slow CBM production is doubtful and the economic benefit of CBM exploitation from high-rank coal can be effectively improved by rapid drainage and pressure reduction. The field experiment results in pilot blocks of Fanzhuang and Zhengzhuang show that by increasing the drainage depressurization rate, the peak production of gas well would increase greatly, the time of gas well to reach the economic production shortened, the average time for a gas well to reach expected production reduced by half, and the peak gas production is higher.
文摘In the past decades,the intense excavation of coal resources in China has induced a series of severe waterrelated disasters or problems,such as water burst accidents,severe groundwater depletion and contamination.All of these problems were caused by the structural changes of roof rocks or bed rocks induced by coal excavation.The structure of collapsed roof rocks is generally classified into three zones:falling zone.
文摘By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point.
基金financially supported by the National Natural Science Foundation of China (Nos.41402138, 41330635, and 41272154)Key Laboratory of Coal-based CO2 Capture and Geological Storage, Jiangsu Province (China University of Mining and Technology) (No.2016B04)
文摘Study on tectonic fractures based on the inversion of tectonic stress fields is an effective method. In this study, a geological model was set up based on geological data from the Hudi Coal Mine, Qinshui Basin, a mechanical model was established under the condition of rock mechanics and geostress, and the finite element method was used to simulate the paleotectonic stress field. Based on the Griffith and Mohr-Coulomb criterion, the distribution of tectonic fractures in the Shanxi Formation during the Indosinian, Yanshanian, and Himalayan period can be predicted with the index of comprehensive rupture rate. The results show that the acting force of the Pacific Plate and the India Plate to the North China Plate formed the direction of principal stress is N-S, NW - SE, and NE - SW, respectively, in different periods in the study area. Changes in the direction and strength of the acting force led to the regional gradients of tectonic stress magnitude, which resulted in an asymmetrical distribution state of the stress conditions in different periods. It is suggested that the low-stress areas are mainly located in the fault zones and extend along the direction of the fault zones. Furthermore, the high-stress areas are located in the junction of fold belts and the binding site of multiple folds. The development of tectonic fractures was affected by the distribution of stress intensity and the tectonic position of folds and faults, which resulted in some developed areas with level I and II. There are obvious differences in the development of tectonic fractures in the fold and fault zones and the anticline and syncline structure at the same fold zones. The tectonic fractures of the Shanxi Formation during the Himalayan period are more developed than those during the Indosinian and Yanshanian period due to the superposition of the late tectonic movement to the early tectonic movement and the differences in the magnitude and direction of stress intensity.
基金supported by the National Natural Science Foundation of China(31672303 to C.Y.,31660617 to L.W.and 31472013 and 31772453 to W.L.)
文摘Several previous studies have indicated that nest sanitation behavior is a general adaptation in altricial birds,with egg recog nition capacity evolvi ng as a specific response to in terspecific brood parasitism(IBP).However,a rece nt study suggested an alternative hypothesis,con cludi ng that con specific brood parasitism(CBP)selects for egg rejection in thrushes,with IBP as a by-product.In the present study,we used a spectrophotometer to quantify egg coloration and egg mimicry and performed artificial parasitism experiments in the grey?backed thrush(Turdus hortulorum).We showed that individuals of this species rejected 100%of 12 foreign eggs,without IBP or CBP detected.In a review of previous studies,we also discuss possible explanations for the high egg rejection rate in the grey-backed thrush and suggest areas for future study.Altricial birds have evolved advaneed reproductive behavior to in crease the fitn ess of their offspring by buildi ng elaborate structures(i.e.,nests),in which they lay eggs and rear their nestlings(Hansell,2000).Bird nests not only provide a suitable place for nestling development,but also act as a concealed location for safety from predators.Furthermore,bird parents have evolved nest sanitation behavior to clean foreig n objects from their n ests,in eluding feces,eggshells,branches,and leaves,because they induce predation,facilitate microorganism growth,damage eggs,or hurt nestlings during brooding(Guigueno&Sealy,2012).Therefore,nest sanitation has evolved as a general behavior in altricial birds for distinguishing between egg-shaped and non-egg-shaped objects.
文摘The rate of lump coal is one of main factors that affects the price of raw coal. The coal mines always puzzle themselves about how to control rate of lump coal effectively. At present, the rate of lump coal is measured mainly by manual operation. The process is inaccurate and the efficiency is low. In this paper, a diameter classification method is proposed to measure the size of lump coal based on image processing.
基金financially supported by East-West Cooperation Project of Ningxia Key R&D Plan(2017BY064)National First-rate Discipline Construction Project of Ningxia(NXYLXK2017A04)。
文摘Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.
文摘A new approach for prediction of face advance rete (FAR) prior to mining operation and determination of the operation efficiency after mining operation in retreat longwall mining panel is presented based upon the concepts of rock engineering system (RES). For this purpose, six longwall panels considered in Parvadeh-I coal mine. Seven major effective parameters on FAR was selected including coal mine roof rating, gas propagation, safety factor of longwall face, ratio of joint spacing to cutting depth at longwall face, longwall face inclination, panel width, floor rock mass rating. To performance evaluation of the presented model, the relationship between the average vulnerability indexes of advance operation with FAR was determined in considered panels with coefficient of determination (R2) equal to 0.884 that indicate relatively acceptable correlation and compatibility. Investigations of the research indicated that it is possible to determine the actual operation efficiency under fair conditions by a RES-based model. The inevitable reduction of FAR for each longwall panel was determined by presented model that the difference amount between the maximum possible practical face advance rate (FARmpp) and recorded actual face advance rate (FARa) indicate the operation efficiency. Applied approach in this paper can be used to prediction of FAR in retreat longwall mining panel for same conditions that can have many benefits, including better and more accurate planning for the sales market and mine operation. Also, presented method in this paper can be applied as a useful tool to determination of actual operation efficiency for other sections and extraction methods in coal mines.
基金sponsored by the Alpha Foundation for the Improvement of Mine Safety and Health, Inc. (Alpha Foundation)the funding provided for this project by the Alpha Foundationpartially funded by the National Institute of Occupational Health and Science (NIOSH) under Grant Number 200-2016-90154.
文摘Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and operations.Previous studies have identified that discontinuous,layered roof materials have some self-supporting capacity.This research is a preliminary step towards understanding these mechanics in coal-measure rocks.Although others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof conditions.The discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in two-dimensions.Model results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)system.Results such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented herein.Potential practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.
基金supported by the National Natural Science Foundation of China (Nos.31301888 and 31672316 to DL)the General Scientific Research Project of the Education Department of Liaoning Province (L2015196 to DL)the Open Fund of the Ministry of Education Key Laboratory for Biodiversity Sciences and Ecological Engineering, Beijing Normal University (K1401 to DL)
文摘Background: The success of cuckoo parasitism is thought to depend largely on the extent of egg matching between cuckoo and host eggs, since poor-matching cuckoo egg would lead to more frequent egg rejection by the host. In this study, we investigated how egg-spot matching between the Common Cuckoo(Cuculus canorus) and its host, the Oriental Reed Warbler(Acrocephalus orientalis) is affected by the local parasitism rate, nest availability in breeding synchronization and egg rejection.Methods: We used the paired design of parasitized and their nearest non-parasitized nests where breeding occurred simultaneously to compare egg-spot matching. The image analysis was used to compare four eggshell pattern variables, namely spot size, density, coverage on the different areas of egg surface, and the distribution on the whole egg surface. Egg recognition experiments were conducted to test the effect of egg spots on egg rejection by the host.Results: Our results show that much better matching in almost all spot parameters tested on the side of the egg and the spot distribution on the whole egg occurred in parasitized nests than in non-parasitized nests. Matching of spot density between cuckoo and host eggs in parasitized nests increased with the synchronization between temporal availability of nests and the egg-laying period of female cuckoos. Egg recognition experiments in which the warbler eggs were deliberately painted with extra spots led to a significantly higher egg rejection rate(78.3%) than of unpainted eggs.Conclusion: Our data suggest that both the high temporal encounter rate between cuckoo and warbler nests as well as the high egg rejection ability of the host are important factors for egg-spot matching of the cuckoos.
基金supported by the Youth Funds of National Natural Science Foundation of China(No.52004173)the Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402)+2 种基金the Science and Technology Innovation Project of Colleges and Universities in Shanxi Province(No.2020L0066)the China Postdoctoral Science Foundation(No.2022M712922)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Nos.2021SX-TD001 and 2022SXTD008).
文摘To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.
基金the sponsor by the National Natural Science Foundation of China (No. 50974115)the Program of Introducing Talents of Discipline to Universities (No.B07028)
文摘The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'an,as one of the state coal mining bases in China,has been seeing increasingly heavier pressure for the protection of water resources.This article considers Lu'an as an example and describes the ways these concerns may be alleviated.High mine-water utilization rates have effectively reduced wasting of water and,consequently,have reduced water demand.Using the top layers of the Ordavician as aquifuge barriers can prevent floor karst water inrush into the longwall face and can protect the regional Ordovician karst water resources at the same time.The strength of the overlying Quaternary clay can protect against roof collapse and has successfully preserved the Quaternary porous water resource.
基金Project(2014QNB31)supported by the Fundamental Research Funds for the Central Universities,ChinaProjects(51674248)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
文摘Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.
基金This work was supported by the Ministry of Science and Higher Education,Poland(No.14303018).
文摘The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air.These concentrations differ in coal heating and cooling phase which was proven in the study.This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating(50–250°C)and cooling(250–35°C)phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed.The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines.Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index.In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane,ethylene,propane,propylene and acetylene,while in the cooling phase these ratios increased systemically.The effect of air(in heating phase)and nitrogen(in cooling phase)flow rate on the self-ignition index CO/CO2 was also determined.
文摘Since mining rights of coal resources(for short MRCR) could be regarded as a multi-stage compound real option,the evaluation for MRCR can be better solved using op- tion theory than the NPV.In the former research,we developed a two-factor model of evaluating MRCR when the coal spot price and convenience yield are stochastic based on option theory.On the basis of this two-factor model,we set up a three-factor model of evaluating MRCR when the interest rate followed a stochastic process.Through a real example application,we found the model can get higher values than the two-factor model and the NPV.This is because considering the volatility of interest rate can improve the executive opportunity of MRCR.
文摘Coal fly ash is being utilized as a recycling material for catalysis due to its aluminosilicate content. Catalytic conversion of polymeric wastes into synthetic gasoline and diesel through pyrolysis requires application of kinetic and thermodynamic principles. This study aimed to identify the catalytic rate constant necessary for rate law involved in reaction mechanisms and activation energy reduction needed for heat transfer rate. Stoichiometric application for balanced total series of elementary reactions is solved for the concentration determination of reactants and products. Unsteady-state in three dimensional directions of thermodynamics is derived for the determination of heat transfer rate, temperatures at any position in a sphere using Gurney and Lurie chart and center temperature in a sphere by Heisler chart. Application principles of rate law and Arrhenius equation can result to thermal conductivity as a function of activation energy leading to synthetic fuel production.
基金The authors would like to thank Dr.Serkan Saydam and Dr.Sungsoon Mo from the University of New South Wales for their kind support and guidance during the preparation of this manuscript.
文摘Estimating the overall floor stability in a coal mine using deterministic methods which require complex engineering properties of floor strata is desirable,but generally it is impractical due to the difficulty of gathering essential input data.However,applying a quantitative methodology to describe floor quality with a single number provides a practical estimate for preliminary assessment of floor stability.The coal mine floor rating(CMFR)system,developed by the University of New South Wales(UNSW),is a rockmass classification system that provides an indicator for the competence of floor strata.The most significant components of the CMFR are uniaxial compressive strength and discontinuity intensity of floor strata.In addition to the competence of the floor,depth of cover and stress notch angle are input parameters used to assess the preliminary floor stability.In this study,CMFR methodology was applied to a Central Appalachian Coal Mine that intermittently experienced floor heave.Exploratory drill core data,overburden maps,and mine plans were utilized for the study.Additionally,qualitative data(failure/non-failure)on floor conditions of the mine entries near the core holes was collected and analyzed so that the floor quality and its relation to entry stability could be estimated by statistical methods.It was found that the current CMFR classification system is not directly applicable in assessing the floor stability of the Central Appalachian Coal Mine.In order to extend the applicability of the CMFR classification system,the methodology was modified.A calculation procedure of one of the CMFR classification system’s components,the horizontal stress rating(HSR),was changed and new parameters were added to the HSR.