Prevention and control of coalfield fire technology:A case study in the Antaibao Open Pit Mine goaf burning area,China

It is very difficult to clearly detect the location of a burning area in a coal mine since it is hidden underground.So we conducted research on the distribution of the burning area before controlling it.Firstly,the original drilling technique was used to analyze and determine the loose and scope of caving of burning area through field test,and then obtained the gases and the temperature data in this area were according to the borehole data.By analyzing these data,we found out that the location of burning area concentrated in the loose and caving area;and finally,the location and development of the burning area within the tested area were accurately determined.Based on this theory,we used the ground penetrating radar(GPR) to find out the loose and caving scale in the burning area during the control process of the burning area,and then located the fire-extinguishing boreholes within target which we used to control burning fire in the section.A mobile comprehensive fire prevention and extinguishing system based on the three-phase foam fire prevention and control technique was then adopted and conducted in the burning area which took only 9 months to extinguish the 227,000 m 2 of burning area of 9# coal.This control technology and experience will provide a very important reference to the control of other coalfield fire and hillock fire in the future.

Numerical simulation for recognition of coalfield fire areas by Rayleigh waves

Effective recognition of a coalfield fire area improves fire-fighting efficiency and helps avoid potential geological hazards. Coalfield fire areas are hard to detect accurately using general geophysical methods. This paper describes simulations of shallow, buried coalfield fires based on real geological conditions. Recognizing the coalfield fire by Rayleigh wave is proposed. Four representative geological models are constructed, namely; the non-burning model, the pseudo-burning model, the real-burning model, and the hidden-burning model. Numerical simulation using these models shows many markedly different characteristics between them in terms of Rayleigh wave dispersion and Eigen displacement. These characteristics, as well as the shear wave velocity obtained by inverting the fundamental dispersion, make it possible to distinguish the type of the coalfield fire area and indentify the real and serious coalfield fire area. The results are very helpful for future application of Rayleigh waves for the detection of coalfield fire area.

A mathematical model of the temperature in a coalfield fire area

The regular pattern of temperature change in a coalfield fire area while the fire is being extinguished was studied. To determine the extinguishing effect, a series of linear, logarithmic, polynomial or exponential mathematical regression models were constructed using the observed temperature data from the Xinjiang coalfield fire extinguishing project. The quadratic polynomial mathematical model had the best fit. A large coal fire oven was also used to simulate the coal fire extinguishing process. The same mathematical regression experiments were carried out on that observed data. The results verified that the quadratic polynomial mathematical model had the best fit. Therefore, a quadratic polynomial mathematical model is proposed to accurately model the temperature-time relationship in a coalfield fire area. An application to coalfield fire suppression shows that the deduced mathe-matical model can be used to predict the temperature conditions and to determine the effect of fire extinguishing, thereby helping to speed up the fire suppression process in the coalfield fire area.

Organic petrographic and mineralogical composition of the No. 6 coal seam of the Soutpansberg Coalfield, South Africa: Insights into paleovegetation and depositional environment

This study investigates the paleodepositional conditions of the No.6 Seam of the Madzaringwe Formation in Makhado and Voorburg south area of the Soutpansberg Coalfield(Limpopo Province,South Africa)utilizing organic petrography and inorganic geochemical proxies.The coals are predominantly high-volatile bituminous B-A rank with high ash yields(avg.36.1 wt%),characterized by high-vitrinite(~41.5 vol%),moderate-to-high inertinite(9.8 vol%–33.7 vol%)and low liptinite(~2.3 vol%).The distribution of inertinite varies among different coal horizons(from bottom-lower to middle-upper),suggesting differential oxidation conditions and/or paleofire occurrence.Vitrinite-to-inertinite(V/I)ratio,tissue preservation–gelification index(TPI–GI),and groundwater–vegetation index(GWI–VI)plots,indicate that the peat-forming forest-swamp vegetation accumulated under mesotrophic-to-rheotrophic hydrological conditions.The presence of structured macerals(i.e.,telinite,collotelinite,fusinite,and semifusinite)suggests well-preserved plant tissues,whereas framboidal pyrite and sulphur content(0.24 wt%–2.16 wt%)point to brackish-water influence at the peat stage.The coals contain quartz,kaolinite,siderite,muscovite,dolomite,calcite,and pyrite minerals,most of which were likely sourced from felsic igneous rocks.The Al/(Al+Fe+Mn)and(Fe+Mn)/Ti ratios for the studied samples range between 0.24–0.97 and 0.57–70.10,respectively.The ratios,Al–Fe–Mn plot,and presence of massive botryoidal-type pyrite imply some influence of meteoric waters or fluids from hydrothermal activity post-deposition.Moreover,the chemical index of alteration(CIA:98.25–99.67),chemical index of weathering(CIW:92.04–97.66),and A–CN–K ternary diagram suggest inorganic matter suffered strong chemical weathering,indicating warm paleoclimatic conditions during the coal formation.

Monitoring coal fires in Datong coalfield using multi-source remote sensing data

Numerous coal fires burn underneath the Datong coalfield because of indiscriminate mining.Landsat TM/ETM,unmanned aerial vehicle（UAV）,and infrared thermal imager were employed to monitor underground coal fires in the Majiliang mining area.The thermal field distributions of this area in 2000,2002,2006,2007,and 2009 were obtained using Landsat TM/ETM.The changes in the distribution were then analyzed to approximate the locations of the coal fires.Through UAV imagery employed at a very high resolution（0.2 m）,the texture information,linear features,and brightness of the ground fissures in the coal fire area were determined.All these data were combined to build a knowledge model of determining fissures and were used to support underground coal fire detection.An infrared thermal imager was used to map the thermal field distribution of areas where coal fire is serious.Results were analyzed to identify the hot spot trend and the depth of the burning point.

Retrieval and Analysis of Coal Fire Temperature in Wuda Coalfield, Inner Mongolia, China

Coal fire burning around the world is an environmental catastrophe characterized by the emission of noxious gases, particulate matter, and condensation by-products. In this study, coal fire temperature is retrieved based on Landsat 5 TM images and Generalized Single-Channel Algorithm (GSCA), in Wuda coalfield, Inner Mongolia, China. Then coal fire zones are extracted by Jenks′ natural breaks and threshold methods based on temperature images. Changes of coal fire zones are analyzed from 1989 to 2008. The results are summarized as follows: 1) The coal fire temperature retrieval method based on Landsat 5 TM and the GSCA model is effective and feasible, because the temperature error is relatively small (from –2.9℃ to +2.6℃) between the measured temperature and the retrieved temperature. 2) The accuracy is relatively high to extract coal fire zones through the Jenks′ natural breaks and threshold methods, because 83.56% of surveyed area is located in the coal fire zones extracted in 2005. 3) The coal fire area increased 9.81 × 10 5 m 2 from 1989 to 2005, and the annual growth is about 6.1 × 10 4 m 2 , with an annual increasing rate of 2.48%. The area of coal fire decreased by 8.1 × 10 5 m 2 from 2005 to 2008.

Spatio-temporal variation and propagation direction of coal fire in Jharia Coalfield,India by satellite-based multi-temporal night-time land surface temperature imaging

In this paper,the spatio-temporal variation and propagation direction of coal fire were studied in the Jharia Coalfield(JCF),India during 2006–2015 through satellite-based night-time land surface temperature(LST)imaging.The LST was retrieved from Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)night-time thermal-infrared data by a robust split-window algorithm based on scene-specific regression coefficients,band-specific hybrid emissivity,and night-time atmospheric transmittance.The LST-profile-based coal fire detection algorithm was formulated through statistical analysis of the LST values along multiple transects across diverse coal fire locations in the JCF in order to compute date-specific threshold temperatures for separating thermally-anomalous and background pixels.This algorithm efficiently separates surface fire,subsurface fire,and thermally-anomalous transitional pixels.During the observation period,it was noticed that the coal fire area increased significantly,which resulted from new coal fire at many places owing to extensive opencast-mining operations.It was observed that the fire propagation occurred primarily along the dip direction of the coal seams.At places,lateral-propagation of limited spatial extent was also observed along the strike direction possibly due to spatial continuity of the coal seams along strike.Moreover,the opencast-mining activities carried out during 2009–2015 and the structurally weak planes facilitated the fire propagation.

The Method and Practice of Constructing 3D Geological Model from Coalfield Exploration 2D Maps

3D geological modeling is an inevitable choice for coal exploration to adapt to the transformation of coal mining for green, fine, transparent and Intelligent mining. In the traditional Coalfield exploration geological reports, the spatial expression form for the coal seams and their surrounding rocks are 2D maps. These 2D maps are excellent data sources for constructing 3D geological models of coal field exploration areas. How to construct 3D models from these 2D maps has been studying in coal exploration industry for a long time, and still no breakthrough has been achieved so far. This paper discusses the principle, method and software design idea of constructing 3D geological model of an exploration area with 2D maps made by AutoCAD/MapGIS. At first, the paper analyzes 3D geological surface expression mode in 3D geological modeling software. It is pointed out that although contour method has unique advantages in coal field exploration, TIN (Triangular Irregular Network) is still the standard configuration of 3D modeling software for coal field. Then, the paper discusses the method of 2D line features obtaining elevation and upgrading 2D curve to 3D curve. Next, the method of semi-automatic partition is introduced to build the boundary ring of the surface patch, that is, the user clicks and selects the line feature to build the outer boundary ring of the surface patch. Then, Auto-process method for fault line inside of the outer boundary ring is discussed, it including construction of fault ring, determining fault ring being normal fault ring or reverse fault ring and an algorithm of dealing with normal fault ring. An algorithm of dealing with reverse fault ring is discussed detailly, the method of expanding reverse fault ring and dividing the duplicate area in reverse fault into two portions is introduced. The paper also discusses the method of extraction ridge line/valley line, the construction of fault plane, the construction of stratum and coal body. The above ideas and methods have been initially implemented in the “3D modeling platform for coal field exploration” software, and applied to the 3D modeling practice of data from several coal field exploration areas in Ningxia, Shanxi, Qinghai, etc.

“十四五”以来新疆煤炭地质工作进展及发展方向

“十四五”以来,新疆煤炭地质工作紧紧围绕煤炭和煤层气勘查开发、煤田灭火、煤矿山生态修复治理开展,取得一系列重要成果和进展,在保障国家能源资源安全、支撑生态文明建设和服务自治区经济社会高质量方面发挥了积极作用。开展煤炭勘查项目约50个,完成钻探进尺60余万米,提交查明煤炭资源量174×10^(8)t,新发现煤炭资源量5.4×10^(8)t,新发现煤炭潜力区2处,为自治区充分释放煤炭优质先进产能和大中型矿井建设提供资源保障;开展煤层气资源调查、勘查和开发项目14个,完成钻探进尺约4.5×10^(4)m,估算煤层气资源量234×10^(8)m^(3)。在阜康大黄山实现了平均单井产量突破,在尼勒克、库拜煤田初步实现了深部煤层气调查和勘查技术突破。立足多年煤炭勘查技术和成果积累优势,围绕煤炭地质服务市场充分发挥作用,大力开展煤田灭火工作,积极拓展采煤塌陷区治理工作,主动服务矿井安全生产。完成火区治理13处,治理火区面积552×10^(4)m^(2);开展煤矿隐蔽致灾因素普查、水文地质类型划分等地质技术服务50余个,为煤矿山安全生产提供了技术保障;塔城地区额敏县采煤沉陷区综合治理恢复耕地10000亩;不断加强科研工作,突破了深部煤层气钻井和大规模压裂技术,形成了一套较完整的火区勘查、治理、监测施工工艺技术体系,初步建立了新疆煤田地质综合信息数字平台。今后,新疆煤田地质将坚持地质找矿核心职能,加强地质科技创新,围绕煤炭、煤层气、战略性关键金属、非金属矿产大力开展找矿突破战略行动,不断提升地灾防治和生态修复治理能力,积极服务生态文明建设。

基于STM32的煤田火区远程智能分级注水系统及应用

传统的注水方法不科学,注水作业工程量巨大且效率低,造成了大量的水资源浪费,为了解决该技术难题,研究了煤田火区远程智能配注技术,将温度参数采集模块、电路控制模块、流量控制阀集成在智能配注器内并长期置于地面,结合无线通信技术及自动调整算法,形成了包括智能配注器、智能测控充电一体仪及地面通信控制主机的智能配注工艺。开发了监测系统远程调整注水流程和测温流程的作业时间,从而控制注水流量,实现了注水流量2 L/s、1 L/s、0.5 L/s的分级调控。新疆三道坝火区的现场试验表明,煤田火区智能分级注水技术可为煤火区智能化灭火提供技术支持。

航空瞬变电磁在将军庙煤田火区勘探中的应用研究

精准测定火区范围对于治理新疆煤田火区具有重要意义。本文采用无人机作为航空瞬变电磁设备载体,获取并处理了奇台将军庙煤田火区的磁测数据,根据火区和正常围岩的磁化强度值存在明显磁异常特征,定性和定量解释出煤层自燃火区的范围及深度。与其他物探方法结果相互验证,确定了着火煤层、火区边界和面积。实践研究表明,所采取的航空瞬变电磁勘查方案具有较高的准确性和可靠性,为“十四五”期间新疆煤田火区的精准勘查和治理提供了良好的借鉴。

Further Information of the Associated Li Deposits in the No.6 Coal Seam at Jungar Coalfield, Inner Mongolia, Northern China

Total 138 coal samples and 14 parting samples were taken from the No. 6 Seam of the Jungar Coalfield, Inner Mongolia. These samples were analysed by optical microscopy, sequential chemical extraction procedure （SCEP）, inductively coupled plasma mass spectrometry （ICP-MS）, X-ray powder diffraction （XRD）, and scanning electron microscope in conjunction with an energy-dispersive X-ray spectrometer （SEM-EDX） analysis. The results indicate that the Li contents have reached the industrial grade of the coal associated Li deposit, and the total Li reserves have reached 2406600 tons, that is, 5157000 tons Li2O in the No. 6 seam in the Jungar Coalfield. The sequential chemical extraction procedure results suggest that the Li concentration is mainly related to inorganic matter. The minerals in the coals consist of kaolinite, boehmite, chlorite-group mineral, quartz, calcite, pyrite, siderite and amorphous clay material. Some Li could be absorbed by clay minerals in the Li-bearing coal seam. The chlorite phase？could be？most likely the host for a part of Li. The Yinshan Oldland should be the most possible source of Li of the coal.

Petrographic characteristics and depositional environment of No.6 coal from Xiaoyugou Mine,Jungar Coalfield,China

This paper discussed the petrographic characteristics of No.6 coal from the Xiaoyugou mine,Jungar Coalfield,Ordos Basin,China.10 samples(7 coal,1 parting mudstone and 2 floor mudstone)were analysed by microscopical and geochemical methods.Four maceral compositions and several associated elements parameters were selected as indicators and corresponding diagrams were drawn to explicate the sedimentary environment.The results indicate that the maceral is dominated by vitrinite and minerals are mainly kaolinite in the No.6 coal.The sedimentary facies vary from barrier island system to tidal-flat which is a deposition process of water body shallowing and the coal-forming plants are herbs and woody plants formed in swamps.

The characteristic and evolution of coal-forming swamp in Hanshuiquan district,Santanghu Coalfield, Xinjiang,NW China,during the Middle Jurassic: evidence from coal petrography,coal facies and sporopollen

Santanghu Coalfield is the largest integrated coalfield exploration area in China. The major coal seams developing in Xishanyao Formation (Middle Jurassic) are the high-quality steam coals characterized by large thickness, favorable horizontal continuity and high coal quality. In this paper, twenty-two samples were collected from the three typical boreholes in Hanshuiquan disirict, representing the 11 coal seam sequences (7#,8#,9#,13#, 14#,15#,17#,18#,19#,20#,22#), respectively. The petrographic characteristics of the coal-bearing sequence in Xishanyao Formation were firstly summarized systematicly, and then the coal-forming swamp characteristics and succession mechanism of the coal seam in Xishanyao Formation were defined by analyzing the samples. The maceral composition, structure, geochemical and geophysical characteristics of coal are in eluded in original genetic criteria of coal-forming swamp an alysis. And the composition of coal petrography, maceral and microlithotype are the most frequently used parameters. Coal is composed of microscopic constituents and inorganic substances. The Xishanyao Formation maceral mainly consists of vitrinite (65.74%-97.01 %), inert i nite (1.93%-34%), and the exinite shows the mode of regular change. The coal-forming swamp in Xishanyao Formation possesses the characteristics of mainly marsh, wet forest swamp facies, and shallow water covered forest swamp facies, and a few of coal seams distribute in the deep water covered forest swamp facies. In addition, the sporopollens in Xishanyao Formation are mainly Pinaceae evergreen broad leaf and needle-leaved plants. Osmundaceae, Cyatheaceae and Lygodiaceae, indicating that the warm and humid tropic-subtropical climate conductive to the persistent growth of coal-forming plants in the Middle Jurassic. The coal-forming swamp shows the characteristics of vertically upward fluctuation through the periodic transition. It indicates a shallow-deep-shallow change process of the water covered depth in the swamp. This is the prin ci pal factor for the formation of the high-quality and continuous coal seam in Hanshuiquan district, Santanghu Coalfield.

Anomalous Concentrations of Rare Metal Elements, Rare-scattered(Dispersed) Elements and Rare Earth Elements in the Coal from Iqe Coalfield, Qinghai Province, China

Total of 23 bench samples were taken from the No. 7 Coal of Iqe Coalfield, Qinghai Province, China, following Chinese Standard Method GB/T 482-2008 （2008）. These samples were analyzed by powder X-ray diffraction （XRD）, inductively coupled plasma mass spectrometry （ICP- MS） and X-ray fluorescence （XRF）. The results indicate that the No. 7 Coal belongs to a low rank （Ro.ran =0.659%） and high-ash coal （40.54%）. Compared to common Chinese and world low-rank coals, the lqe coal contains anomalous concentrations of rare metal elements, rare-scattered （dispersed） elements and rare earth elements. The highest contents of Rb, Cs, Ga and REY reach to 180, 26, 37, and 397 ppm, respectively. Their average contents of these elements are 10.9, 15, 4.8 and 3.5 times higher than those of world coals, respectively. Minerals in the coal include kaolinite, quartz, muscovite, siderite, and traces of rutile, and brookite. Kaolinite could be main host minerals of Rb, Cs, Ga and REY. The anomalous rare element Rb and Cs accumulation in the Iqe coal is related to both organic and inorganic matter. The REY concentrations may be related to circulation of thermal solutions, contained or sorbed by clayey particles, and organic matter as well.

Technology of groundwater reservoir construction in goafs of shallow coalfields

In exploiting shallow coal resources in western China, conservation of water resources is often subjugated to considerations of safety and production in coal mines. In order to maintain a sustainable development in the Shenfu-Dongsheng coalfield, we propose a technology of constructing groundwater reservoirs in goafs in shallow coalfields to protect fragile ecological environments. Given the premise of safe production, we selected an appropriate goaf as the site for constructing a groundwater reservoir and used a mine water recharge technique in combination with other related techniques for effective water conservation. Then filtering and purification techniques were used to purify the mine water given the physical and chemical properties of mine water and its filling material, ,thereby greatly reducing suspended matter, calcium and other harmful ions in the water. With the potential of widely application, the research result has been successfully applied in the Daliuta coal mine, to great economic and ecological effect. Therefore, this achievement provides a new way for mine water conservation in shallow coal resources in western China.

Research on Potential Fertilization of Coal Gangue in the Weibei Coalfield,China

Based on the systematic analysis of the coal gangue in Weibei Coalfield, such as petrologic characteristics, chemical composition, nutrient elements, deleterious elements, and the transformation, and compared with the soil element content background values of Loess Plateau and national harmful materials controlling standards, we conclude that the coal gangue in the Weibei Coalfield has huge potential to be used as clay fertilizer.

Experimental study on the oxidation kinetics of coal in typical coal mining areas of the Southern Junggar coalfield,Xinjiang,China

Coal spontaneous combustion(CSC)is a disaster associated with coal mining that leads to loss of coal resources and envi-ronmental and human health issues.To investigate kinetic characteristics for oxidation of coal,three coal samples were collected from different coal mining areas in the Southern Junggar coalfield.Subsequently,the collected coal samples were ground into different particle sizes and tested using microscopic and macroscopic methods,including thermal gravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffraction,and temperature-programmed oxidation.The results obtained are as follows:the sharpest absorption peak(002)indicates that graphitization is high.Furthermore,the results show that the SKS coal sample is prone to spontaneous combustion;the greater the aromatic hydrocarbon content is,the more difficult it is for CSC to occur,while the opposite is true for oxygen-containing functional groups.The SKS data confirmed this conclusion;the rate for generation of CO and CO_(2)controlled the possibility of SKS oxidation at 110℃and provided an indication of the temperature.During the dehydration stage,the WD sample had the lowest activation energy,indicating that it was most susceptible to spontaneous combustion.During the combustion stage,the lowest activation energy was found for the SKS sample with particle sizes<0.075 mm,indicating that particle size was one of the factors affecting spontane-ous combustion.The activation energy for dehydration was significantly lower than that for combustion,which showed that the coal oxygen reaction was more likely to occur in the dehydration stage.Based on DSC curves,the SKS sample had the largest exothermicity,indicating that it would ignite more readily.

Coalfield structure and structural controls on coal in China

The occurrence of coal-bearing strata in a variety of coal-bearing basins of China is characterized by late tectonic deformation and remarkable spatial and geochronologic differences.The main controlling factors,which determine the tectonic framework of coalfields,include the geodynamic environment,tectonic evolution,deep structures,tectonic stress,and lithologic combination of the coal measures.The Chinese continent has experienced multi-stage tectonic movements since the Late Paleozoic.The spatial and temporal heterogeneity of its continental tectonic evolution,the complexity of its basement properties,and its stratigraphic configurations control the tectonic framework of its coalfields’present complex and orderly patterns.The concept of coal occurrence structural units is proposed in this paper and is defined as the structural zoning of coal occurrence.China’s coalfields are divided into five coal occurrence structural areas,and the structural characteristics of the coalfields in five main coal occurrence areas throughout the country are summarized.Based on the analysis of the relationship between the structure characteristics and occurrence of coal in these coalfields,the coal-controlling structures are divided into six groups:extensional structural styles,compressional structural styles,shearing and rotational structural styles,inverted structural styles,sliding structural styles,and syn-depositional structural styles.In addition,the distribution of coal-controlling structural styles is briefly summarized in this paper.

Environmental Investigation and Evaluation of Land Subsidence in the Datong Coalfield Based on InSAR Technology

Heavy mining of Jurassic and Carboniferous horizontal coal seams in the Datong coalfield has seriously affected the local geological environment, which is mainly manifested by such geohazards as soil avalanches, landslides, mudflows, surface subsidence, surface cracks, surface solid waste accumulation and surface deformation. More seriously, coal mining causes groundwater to leak. Overpumping of groundwater has resulted in substantial land subsidence of the urban area in Datong City. Based on the previous geo-environmental investigation in the work area, the authors used radar remote sensing techniques such as InSAR （synthetic aperture radar interferometry） and D-InSAR （differential synthetic aperture radar interferometry）, supplemented by the optical remote sensing method, for geo-environmental investigation to ascertain the geo-environmental background of the Datong Jurassic and Carboniferous-Permian coalfield and evaluate the effects of the geohazards, thus providing a basis for the geo-environmental protection, geohazard control and prevention, land improvement and optimization of the human environment. In this study 8 cog-nominal ERS-1/2 SAR data frames during 1992 to 2003 were used, but the following processing was made： （1） the multitemporal SAR magnitude images were used to interpret the geological structure, vegetation, microgeomorphology and drainage system; （2） the multi-temporal InSAR coherent images were used to make a classification of surface features and evaluate the coherence change due to coal mining; and （3） the multi-temporal cog-nominal SAR images were used to complete D-InSAR processing to remove the information of differential deformation areas （sites）. In the end, a ten-year time series of differential interferograms were obtained using the multi-temporal cog-nominal SAR images. In the tests, 84 deformed areas （sites） were obtained, belonging to those in 1993-1996, 1996-1997, 1997-1998, 1998-2001, 1998-2002 and 2001-2003 respectively. Of the 84 areas, 44 are mining subsidence ones, 23 urban subsidence ones and 17 landslide subsidence ones. They cover a total area of 1824.4 km^2, equivalent to the area of the whole Datong coalfield. Then an accurate evaluation was made on the geo-environment of the Datong coalfield. The tests show that InSAR is now the only feasible technical means for making one all-weather, real-time measurement of a coal mining land subsidence area covering up to 10,000 km^2 to subcentimeter resolution. This study is a successful application of InSAR in the investigation and evaluation of land subsidence, especially in coal mining areas.