assessment of the contribution of in situ combustion of coal to greenhouse gas emission based on a comparison of chinese mining information to previous remote sensing estimates greenhouse gas ghg emission from geological sources such as volcanic activity seabed gas hydrate release hydrocarbon seepage as well as uncontrolled combustion of fossil fuels is erratic and difficult to quantify in this paper we assess the ghg emission due to spontaneous combustion of in situ coal deposits coal fires this problem is aggravated by human intervention mining activities which on the other hand allows better constrained estimations and improved reduction strategies provided modern mining practices are employed in this study we present three case studies on coal fire related ghg emission quantification on provincial scale in china and we propose an integrated quantification aimed at the joint analyses of local knowledge geophysical data and remote sensing data with the objective to retrieve unbiased numbers as a first estimate we conclude that the emissions of ghgs from coal fires in china account for well less than 0 22 of all global fossil fuel related co2 emissions most likely even less than 0 1 this is much less than the previously estimated 2 3

impact of underground coal fire on coal petrographic properties of high volatile bituminous coals a case study from coal fire zone no 3 2 in the wuda coalfield inner mongolia autonomous region north china abstract the wuda coalfield located in the inner mongolia autonomous region north china is known as one of china s major source of prime coking coals and a site of well researched and well documented underground coal fires the underground coal fire at the coal fire zone no 3 2 is situated in the active coal mine of suhai tu located in the north westerly part of the wuda coalfield the present paper investigates the impact of the underground coal fire on the coal seam no 10 by application of coal petrographic methods including detailed characteristic of macerals and other coal components maceral analysis microstructural analysis and vitrinite reflectances performed on 1 coal grains lacking impurities microfractures dark oxidation rims 2 on dark rimmed vitrinite as well as 3 on low temperature semi coke the investigated coal seam no 10 represents a high volatile a bituminous coal and is dominated by vitrinite followed by inertinite with minor amounts of liptinite and by non isotropic low temperature semi coke the microstructure of the oxidatively and thermally altered coals is represented by 1 extensive non tectonic microfissures and non tectonic microfractures i e shrinkage microfractures leading to defragmentation of coal grains 2 dark oxidation rims observed at grain margins non tectonic microfissures and microfractures and by 3 devolatilisation micropores random vitrinite reflectances measured in 1 coal grains lacking impurities microfractures and dark oxidation rims and in 2 dark rimmed vitrinite at non tectonic microfissures and fractures reveal significant lateral variations the presence of low temperature semi coke and its marked lower reflectance values are indicative of thermal alteration induced by the underground coal fire in the coal fire zone no 3 2 the results obtained from the performed analyses of organic matter point to both low temperature oxidation and low temperature pyrolysis processes the applied coal petrological approach revealed characteristic changes to the coal s microstructure its petrographic composition as well as to optical properties induced by the underground coal fire

aquifer protection during longwall mining of shallow coal seams a case study in the shendong coalfield of china large scale underground mining of shallow coal seams can have significant impacts on ground surface and potentially leads to incidental damage to the overlying aquifer with subsequent environmental hazards in order to deal with the apparent conflict between water protection and high production in underground mining an aquifer protection mining technique was trialed in panel 51201 in the shangwan colliery the shendong coalfield china overburden failure water level of the unconsolidated aquifer surface cracks and ground subsidence were monitored in a series of boreholes using borescope and also by observations in a nearby water well and by surface surveys monitoring results indicate that the aquifer protection mining technique can be successfully applied by modifying a few mining parameters such as mining height or advance rate under some suitable geological conditions the critical zone in the stratigraphy appears to be the weathered bedrock located immediately below the aquifer the weathered bedrock will remain impermeable after mining as long as its thickness is greater than the mining height the development of the mining induced overburden failure is affected by the key strata but ultimately controlled by the soft aquiclude such as the weathered zone it was observed respectively that the height of the caved zone was observed to be 5 to 6 times the mining height whilst the height of the fractured zone is about 10 to 11 times the mining height

field trials of aquifer protection in longwall mining of shallow coal seams in china the large scale mining of shallow coal seams has a significant impact on the overlying aquifers and surface ecological environment to protect the aquifers and maximize the coal resource recovery field trials were undertaken during the operation of the lw32201 in bulianta coal mine shendong china with a severely weathered rock swr layer and two key strata ks in the overlying strata aquifer protection in longwall mining aplm relies mainly on the rapid advance in some localized zones special measures should be taken to achieve the aplm including lowering mining height backfill and slurry injection to further understand the mechanism and applicable conditions of the aplm and validate the effectiveness of the aplm variation of the water table in the aquifer was observed as the longwall face passed through the zone this paper also discusses the mechanism and basic requirements of the aplm and the relationship between the fall of the water table and the surface subsidence the results of the field trials indicated that aplm in shallow coal seams could be successful under suitable conditions

rare earth element complexation behavior in circumneutral ph groundwaters assessing the role of carbonate and phosphate ions rare earth element ree concentrations were determined in circumneutral ph 7 ph 9 groundwaters from south central nevada and the mojave desert in eastern california u s a the inorganic speciation of the rees in these water were evaluated primarily to assess the relative importance of carbonate lnhco32 lnco3 and ln co3 2 and phosphate lnh2po42 lnhpo4 ln hpo4 2 and lnpo40 complexes other ree complexes with sulfate hydroxyl chloride and fluoride ions were also assessed as was the significance of the free metal ion species i e ln3 our speciation calculations indicate that ree carbonate complexes dominate and typically account for more than 99 of each ree in solution moreover carbonato complexes lnco3 were predicted to be the dominant species for the light rees and dicarbonato complexes ln co3 2 were predicted to increase in importance with increasing atomic number all other complexes were predicted to be negligible furthermore the combined percentage of all ree phosphate complexes never accounted for more than 0 1 of the dissolved rees and generally much less than 0 1 phosphate complexes can not compete with carbonate complexes in these groundwaters because of the low po43 concentrations 0 3 1 58 mol kg the much lower concentrations of the free phosphate ion i e po43 f 10 9 10 6 mol kg due to ion pair formation with ca2 and mg2 and the much higher free carbonate ion concentrations co32 f 0 32 87 mol kg

analysis of developmental features and causes of the ground cracks induced by oversized working face mining in an aeolian sand area in order to satisfy the energy demand of china it is an effective way to exploit coal resources efficiently in western china when a coal seam with a shallow burial depth is mined on a large working face with width of 300 m in a semi desert aeolian sand area of western china the induced subsidence and damage of ground surface are remarkably different from those induced by a traditional mining condition by taking working face 12 406 of bulianta coalmine in shendong mining area as an example this paper based on actual measurement data analysed the developmental features and causes of ground surface racks research results showed that the shape of the static crack in the peripheral area on the working face was very similar to that contained in the actual measurement results of other areas specifically such static crack was arc shaped and the actually measured static crack angle was 84 5 however the dynamic crack above the working face took on uniqueness in two developmental cycles expansion to restoration this phenomenon is not available in other research areas starting from the structure of rock strata this paper analysed the two developmental cycles of dynamic cracks according to the periodic fracture theory of key stratum and verified the results of theoretical analysis by employing the similar material model

mining induced strata stress changes fractures and gas flow dynamics in multi seam longwall mining abstract this paper presents key findings from a recent comprehensive study of longwall mining induced strata movement stress changes fractures and gas flow dynamics in a deep underground coal mine in anhui china the study includes field monitoring of overburden displacement stress and water pressure changes at the longwall panel 1115 1 of the guqiao mine in addition 3d modelling of strata behaviour at the longwall panel using a 3d finite element code and goaf gas flow simulations with a cfd code are carried out this research has resulted in many new insights into the complex dynamic interaction between mining induced strata stress changes fractures and gas flow patterns based on the findings from the field monitoring and numerical modelling a three dimensional annular shaped overlying zone along the perimeter of the longwall panel is identified for optimal methane drainage during mining a practical method that helps define the geometry and boundary of this zone is proposed this study provides a new methodology and a set of engineering principles for the design of optimal co extraction of coal and methane

development law of air leakage fractures in shallow coal seams a case study in the shendong coalfield of china continuous air leakage from ground mining induced cracks is a significant cause of coal spontaneous combustion low oxygen at the working face and other disasters in shallow coal seams this paper studies mining induced cracks and air leakage caused by the repeated mining of shallow coal seams at the bulianta coal mine shendong coalfield china a similar simulation experiment was carried out in the laboratory and then the ground mining induced cracks were observed and the crack air leakage was detected the results showed that the surface air flowed into the composite goaf before the fractures redeveloped to the surface during the process of lower coal seam mining due to the different development processes of vertical fractures in various regions the width of the vertical fractures in the boundary area of the overlying goaf increases significantly after the repeated mining of coal seams while the vertical fractures in the central area of the overlying goaf experience almost no change the distribution of the surface air leakage cracks is in the shape of graben type cracks and half graben type cracks are surface air leakage cracks which are the focus of surface air leakage problems especially the half graben type cracks the results are important in engineering for reducing air leakage from surface mining induced cracks

the comparative behaviors of yttrium and lanthanides in the seawater of the north pacific yttrium has long been recognized as an ekalanthanide because of its chemical contiguity relative to the chemistries of rare earth elements which are in recent years intensively utilized for elucidation of metal scavenging processes in the ocean here we present the first detailed depth profile of y iii in seawater together with the lanthanides in the north pacific ocean the concentrations of y iii range 70 290 pmol kg and show the nutrient like profile best resembling that of ho iii amongst the other rare earth elements the results agree well with an expectation based on the similarity in their ionic radii and hence stability constants of complexation with carbonate ions yet the ho iii y iii ratios in seawater systematically increase with depth suggesting that y and ho are fractionated during scavenging by natural marine particulates this is likely to result from the different complexation behavior in that y iii is more weakly complexed than ho iii with soft organic ligands on the surface of particulate matter during scavenging in the surface water but once released into seawater in the deep sea y iii is complexed with carbonate ions equally or stronger than ho the pattern of deep water enrichment in the lanthanide series appears to be consistent with the recent observation of partitioning between suspended particles and seawater our precise measurements also indicated that pr and tb best resemble nd and dy respectively in their oceanic behavior whereas ho and tm are intermediate between their neighboring rare earth elements

simulating mining induced strata permeability changes abstract mining processes fracture the surrounding strata and may modify the flow of groundwater by inducing new fractures or changing the permeability of existing defects the result of mining induced permeability changes can be disturbance to aquifers or other surface or sub surface water bodies traditional methods for predicting mining induced fracture connectivity and enhanced permeability based on empirical strain based criteria may not satisfy modern regulatory demands nor adequately reflect local geological geotechnical and hydrogeological conditions standard continuum numerical methods may indirectly estimate permeability enhancement from plastic strains however they are not able to track aperture on flow paths or predict fracture connectivity this paper presents a numerical approach that is demonstrated to be capable of representing longwall mining induced fracturing in sedimentary rock masses by initiating and propagating fractures determining connectivity and calculating aperture in a piecewise manner on flow paths we have estimated permeability enhancement from first principles fracture intensity and porosity metrics are calculated and identify the height of the enhanced permeability fractured zone above a longwall goaf permeability within the overburden is estimated from the kozeny carman permeability porosity equation at a mine site studied in detail in this paper a permeability increase from the in situ state is predicted to range from approximately eight orders of magnitude in the caved zone to one to two orders of magnitude in the strata above the fractured zone realistically simulating cracking fracturing and crushing of rock strata remains numerically intensive and challenging at the scale of a longwall panel it is demonstrated in this paper and provides valuable insights into the rockmass response to mining

self organization of river networks to threshold states numerical models in which grid cells self organize so that the shear stress in each cell equals a predetermined threshold value are remarkably successful in producing the fundamental structure of river networks such models are a reasonable approximation of networks characterized by near constant dimensionless shear stress bed shear stress7sol bed grain size with each cell s threshold value being proportional to median bed grain size previous work has shown that this is the case for channels cut into alluvium and that the characteristic narrow range of is different for gravel and sand bed channels channels in the italian apennines that are slowly incising into weak bedrock but which are covered by a veneer of gravel for most of the time are shown to be characterized by the same as alluvial gravel bed channels thus threshold models capture the fundamental behavior of many river networks even in areas of long term bedrock incision

soil and water conservation in mining area based on ground surface subsidence control development of a high water swelling material and its application in backfilling mining it has always been a crucial issue in the mining industry that the surface subsidence induced by underground coal mining can lead to the severe deterioration or loss of soil and water resources in mining area backfilling has become one of the most frequently used mining method to solve this puzzle as it can effectively control the movement of overlying strata and therefore soil and water resources will not be destroyed by mining activities a new type of high water swelling material hwsm was developed to address the key issues of current backfilling materials used in collieries such as the high cost inadequate strength and low expansion rate based on the principle that the strength of backfilling body satisfies the requirement a critical ratio of water to solid material a mixture of fly ash which was used as an aggregate lime anhydrite cement and additive ingredients was determined which varied from 0 8 1 to 0 9 1 meanwhile the mass ratio of fly ash anhydrite lime cement and additives was determined to be 24 6 0 8 5 1 1 8 1 laboratory tests showed that strength of samples that met the required setting time for practical use could reach 5 39 5 52 mpa after 63 days the expansion rate after 3 h varied between 9 9 and 10 8 and the bleeding rate ranged from 0 3 to 0 33 industrial application has been conducted in wangtaipu colliery and results showed that the proposed hwsm had an outstanding mechanical performance with good expansion rates and fluidity these properties indicate that the developed material is suitable for use as a good backfilling material in mining so as to effectively reduce the ground surface subsidence and to conserve the soil and water

surface stepped subsidence related to top coal caving longwall mining of extremely thick coal seam under shallow cover the surface stepped subsidence had badly affected the public infrastructure safety the formation mechanism of the surface stepped subsidence case was explained the surface subsidence profile after the sequent mining activity was predicted the possible controls of the stepped subsidence were lastly proposed

coal fires revisited the wuda coal field in the aftermath of extensive coal fire research and accelerating extinguishing activities abstract the wuda coal mining area in inner mongolia autonomous region china is one of the largest coal fire areas world wide at the same time it is also one of the most extensively researched ones the sub surface coal fires raging in the underground coal seams of the syncline are located directly west of the town of wuda the fires have been mapped in situ based on remote sensing data as well as based on geo physical survey all throughout the years 2001 to 2005 numerous publications depict the situation during that time in the present study we assess the current situation in wuda coal field five years after the last field campaigns under nowadays on going and accelerating extinguishing activities we present the results of coal fire dynamics assessment based on in situ mappings between 2004 and 2010 the analyses of changes in mining infrastructure between 2005 and 2012 as well as land cover change in the area from 2005 to 2012 newest high resolution multispectral and panchromatic quickbird data as well as time series of quickbird data supported this endeavor we furthermore present the result of semi structured interviews undertaken with members of the local mine directorate of the wuda syncline all jointly analyzed data indicate that the wuda coal fires tend to move eastwards within the syncline meaning that they move along the dip of the coal seams to greater depths furthermore mining related infrastructure is clearly moving from the west to the east as well despite large funds spent on fire extinguishing only few fires remain permanently extinct while other fire areas increase in size the former land cover structure in the arid syncline does not exist anymore extinguishing activities have led to a complete turn over of all material in the region the coal fire problem in wuda area remains a pressing one

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

the lanthanide tetrad effect and its correlation with k rb eu eu sr eu y ho and zr hf of evolving peraluminous granite suites lanthanide tetrad effects are often observed in ree patterns of more highly evolved variscan peraluminous granites of mid eastern germany central erzgebirge western erzgebirge fichtelgebirge and northern oberpfalz the degree of the tetrad effect te1 3 is estimated and plotted vs k rb sr eu eu eu y ho and zr hf the diagrams reveal that the tetrad effect develops parallel to granite evolution and significant tetrad effects are strictly confined to highly differentiated samples mineral fractionation as a cause for the tetrad effect is not supported by a calculated rayleigh fractionation which also could not explain the fractionation trends of sr eu and eu eu the strong decrease of eu concentrations in highly evolved rocks suggests that eu fractionates between the residual melt and a coexisting aqueous high temperature fluid mineral fractionation as a reason for the tetrad effect is even more unlikely as ree patterns of accessory minerals display similar tetrad effects as the respective host rocks the accessory minerals inherit the ree signature of the melt and do not contribute to the bulk rock tetrad effect via mineral fractionation these results point in summary to significant changes of element fractionation behavior in highly evolved granitic melts ionic radius and charge which commonly control the element distribution between mineral and melt are no longer the exclusive control the tetrad effect and the highly fractionated trace element ratios of y ho and zr hf indicate a trace element behavior that is similar to that in aqueous systems in which chemical complexation is of significant influence this distinct trace element behavior and the common features of magmatic hydrothermal alteration suggest the increasing importance of an aqueous like fluid system during the final stages of granite crystallization the positive correlation of te1 3 with bulk rock fluorine contents hints at the importance of ree fluorine complexation in generating the tetrad effect as the evolution of a ree pattern with tetrad effect m type implies the removal of a respective mirroring ree pattern w type the tetrad effect identifies open system conditions during granite crystallization

a new method for the determination of ceiii ceiv ratios in geological materials application for weathering sedimentary and diagenetic processes abstract relative abundances of rare earth elements ree in geological materials are used widely to investigate diverse geochemical issues such as the origins of igneous rocks or the degree of stratification of water columns in oceans one of the ree cerium ce can exist in either trivalent or tetravalent forms depending on the redox condition thus knowledge of the oxidation state of ce in rocks and minerals could potentially be used to constrain the redox states of past and present geological environments however the use of ce for this purpose has been hampered by an inability to measure its oxidation state directly here we present a new method employing the x ray absorption near edge structure for making such determinations in samples with ce concentrations as low as 15 ppm by analyzing a range of diverse geological materials granites manganese nodules and cherts we showed that the method could identify significant differences in ce speciation between materials formed under widely differing redox conditions used together with the degrees of ce anomalies measured in ree patterns this information has promise for refining our knowledge of various geochemical processes such as weathering sedimentary and diagenetic processes that control the ree behavior such a refinement should in turn improve geological interpretations based upon ree data

separation and fracturing in overlying strata disturbed by longwall mining in a mineral deposit seam abstract mining induced fractures influence the stability of overburden and may provide pathways for transferring heat and mass in underground environment a novel approach was proposed to quantify the separation and fracture evolution in the undermined overburden consisting of 1 theoretical distribution models of the void ratios of fractures vrfs based on analytical evaluation of key strata subsidence and 2 numerical modeling using the universal distinct element code and a sequence of image post processing procedures for a longwall mining panel both theoretical calculations and numerical simulations indicated that vrf first increased rapidly then gradually decreased and finally stabilized to a minimum from the surrounding edges of disturbed strata to their centers and gradually decreased from deep to shallow strata the fractures exhibited a fracture rich arch distribution type along a vertical section numerous fractures occurred around the arch feet near the perimeters of mined out area and or arch crown near the center of disturbed strata the distributions of vrfs show the heights shapes and damage intensities of fractured zones and can also be used as porosity parameters to determine the permeabilities of mining disturbed overburdens therefore the vrf models can be used as a quantitative parameter to assess the extent of possible risk zones e g for water inflow into the mine or escape of hazardous fluids to the surface

w and m type tetrad effects in ree patterns for water rock systems in the tono uranium deposit central japan abstract abundances of rare earth elements plus y ree were determined for granitic rocks tertiary sedimentary rocks and related groundwater in the tono area central japan tetrad effects concave curves in ree patterns were found for these rocks and groundwater samples conjugate m and w types of tetrad effects were simultaneously observed in these specimens which constitute the water rock system the granitic rocks show the m type tetrad effects while the groundwater and the sedimentary rocks exhibit the w type tetrad effects non chondritic y ho ratios were found especially in the groundwater y ho ratios showed larger values than the chondritic value for the samples showing w type tetrad effects and vice versa these results suggest that 1 preference of the groundwater for a w type tetrad effect and larger y ho ratio than chondrite produces an m type tetrad effects and lower y ho ratios in the granitic rocks during weathering processes 2 the w type tetrad effect and larger y ho ratio for the sedimentary rocks is brought about by the fixation of groundwater ree onto the sedimentary rocks the variation of the tetrad effect and y ho ratio was confirmed by laboratory experiments on the leaching of ree from the granitic rocks the w type tetrad effect and large y ho ratio in the u mineralization zone in the sedimentary rocks were also found by sims analysis which is consistent with the w type tetrad effect and larger y ho ratio in the whole rock abundances of the sedimentary rocks disequilibrium of the u series 234 u 238 u analyzed by sims in the u mineralization zone suggests that the u bearing minerals were formed through precipitation from groundwater as it became reducing these results suggest that the ree in the sedimentary rocks were transported by the groundwater from the granitic rocks in the tono area based on this study it is implied that the degree of the tetrad effects and the variation of y ho ratio can be valuable tools to investigate the migration of ree during water rock interactions in natural systems

evolution mechanism of water flowing zones and control technology for longwall mining in shallow coal seams beneath gully topography the height and evolution mechanism of fractured water flowing zones are of great importance for prevention of water inrush disasters and protection of immediate environments particularly in ecological vulnerable areas in this paper comparative approaches including empirical formula calculation physical simulation numerical simulation and protem transient electromagnetic analysis are employed to identify the development of the fracture zones caused by water flowing so as to ensure mining safety and protection of groundwater in shallow coal seams beneath gully topography an empirical formula was used to calculate the height of the water flowing fracture zone and an experimental study utilizing a model based on a similar material was adopted to analyze the movement and fracture development of the overlying strata results provide a reasonable basis from which a rational mining height may be determined the protem transient electromagnetic apparatus was employed to detect the water flowing structure conductivity of the overlying strata induced by mining beneath gully topography in the field the water flowing fracture of the overlying strata can be estimated according to comprehensive analysis of the apparent resistivity changes of the field gully surface crack development and aquifer water level accordingly the control technologies in the field were implemented and discussed regarding preventing gully water from rushing into underground mining spaces through water flowing fracture zones results indicate that safe and efficient mining of shallow seams beneath gully topography can be achieved by prevention of gully accidents and protecting the surface water resources of the ecological environment

rare earth element geochemistry and the tetrad effect abstract the tetrad effect is found in the rare earth elements la lu and results from increased stability at quarter half three quarter and complete filling of the 4f electron shell suggestions that this effect is observed in ree patterns of seawater and other geological samples marine phases the mineral kimuraite late stage granitic rocks the mineral uraninite and siliciclastic sediments are not compelling in the cases of seawater and the carbonate mineral kimuraite a discontinuity at gd may be attributed to the tetrad effect but the complexity of the overall controls on these ree distributions leaves such an interpretation uncertain at best unusual ree patterns in leucogranites and pegmatites are best explained by fractionation of trace minerals notably apatite apparent tetrad anomalies in uraninite rees disappear when normalised to upper crustal i e shale abundances analytical difficulties probably explain apparent tetrad effects in some seawater limestone and siliciclastic ree patterns