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.

Numerical analysis of stability for mined-out area in multi-field coupling

There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.

Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area

Dynamic analysis steps and general flow of fast lagrangian analysis of continua in 3 dimensions(FLAC3D) were discussed. Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area was carried out with FLAC3D. The whole analytical process was divided into two steps, including the static analysis and the dynamic analysis which were used to simulate the influence of excavation process and blasting vibration respectively. The results show that the shape of right upper boundary is extremely irregular after excavation, and stress concentration occurs at many places and higher tensile stress appears. The maximum tensile stress is higher than the tensile strength of rock mass, and surrounding rock of right roof will be damaged with tension fracture. The maximum displacement of surrounding rock is 4.75 mm after excavation. However, the maximum displacement increases to 5.47 mm after the blasting dynamic load is applied. And the covering area of plastic zones expands obviously, especially at the foot of right upper slope. The analytical results are in basic accordance with the observed results on the whole. Damage and disturbance on surrounding rock to some degree are caused by excavation, while blasting dynamic load increases the possibility of occurrence of dynamic instability and destruction further. So the effective supporting and vibration reducing measures should be taken during mining.

Instability identification on large scale underground mined-out area in the metal mine based on the improved FRBFNN

To identify the instability on large scale underground mined-out area in the metal mine effectively,the parameters of radial basis function were determined through clustering method and the improved fuzzy radial basis function neural network(FRBFNN)model of instability identification model about large scale underground mined-out area in the metal mine was built.The improved FRBFNN model was trained and tested.The results show that the improved FRBFNN model has high training accuracy and generalization ability.Parameters such as pillar area ratio,filling level and the value of rock quality designation have strong influence on instability of large scale underground mined-out area.Correctness of analysis about the improved FRBFNN model was proved by the practical application results about instability discrimination of surrounding rock in large-scale underground mined-out area of a metal mine in south China.

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.

Quantitative analysis of biotechnical reinforcement for a steep slope consisting of composite coal-gangue-soil medium adjacent to a mined-out area

The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vegetation and porous characteristics of the soil and rock mass, the steep slope will be destabilized and induce mud-rock flow or derive hazard easily. Firstly, based on the classical slope reinforcement theory, some regularity between the shear and displacement in the destabilized zone of the slope with or without root strength contribution is presented. Then, based on the experimental and statistical analysis of root strength, hydrological characteristics and stability status, etc., some possible biotechnical techniques for reinforcement of the steep slope have been suggested. These methods are important for quantitative analysis of destabilization of the slope and design of the biotechnical reinforcement.

Time function of surface subsidence based on Harris model in mined-out area

The surface subsidence is a common environmental hazard in mined-out area. Based on careful analysis of the regularity of surface subsidence in mined-out area, we proposed a new time function based on Harris curve model in consideration of the shortage of current surface subsidence time functions. By analyzing the characteristics of the new time function, we found that it could meet the dynamic process, the velocity change process and the acceleration change process during surface subsidence. Then its rationality had been verified through project cases. The results show that the proposed time function model can give a good reflection of the regularity of surface subsidence in mined-out area and can accurately predict surface subsidence. And the prediction data of the model are a little greater than measured data on condition of proper measured data quantity, which is safety in the engineering. This model provides a new method for the analysis of surface subsidence in mined-out area and reference for future prediction, and it is valuable to engineering application.

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.

基于时序InSAR的山西大同煤田地表沉降监测及时空演化分析

[研究目的]地表沉降作为煤矿区主要地质灾害之一,严重影响矿区经济的可持续发展和居民生活的安全稳定,有必要对矿区地表沉降进行快速高效监测。[研究方法]以大同煤田为例,研究使用2020年1月至2021年12月共31景Sentinel-1影像,基于短基线集干涉测量技术(Small Baseline Subset InSAR,SBAS-InSAR)对地表沉降进行监测,获取大同煤田地表沉降速率和累计沉降结果,使用已有研究成果对监测结果的可靠性进行验证,并分析了沉降时空变化特征及演化规律。[研究结果]大同煤田地表沉降分布较广,沉降总体分布趋势与大同煤田矿业管理数据的走向基本一致。沉降主要分布在大同市南郊区西部以及大同市、怀仁市和山阴县交界处,其中塔山矿地表沉降最为严重,大同煤田最大沉降速率为168.03 mm/a,最大累计沉降量为329.12 mm,总沉降面积为270.95 km^(2),且沉降呈现持续增加的趋势,根据沉降趋势推断需要较长时间才能实现地表活动相对稳定。[结论]研究表明了InSAR技术在煤矿区沉降监测的可行性,可为矿产资源管理工作提供新的技术方法,研究结果可为煤矿区沉降监测预警、灾害防控及资源合理开发利用提供科学依据。

半干旱草原露天矿区生态累积效应:评估模型与应用

为揭示半干旱草原露天矿区生态环境质量状况,分离矿区人类活动生态累积效应并识别其演变态势,在厘清矿区生态累积效应概念的基础上,构建适用于半干旱草原的露天矿区生态环境质量评估指数(Surface Mining Areas Eco-environmental Evaluation Index,SMAEEI)以及矿区生态累积效应定量评估模型。选取内蒙古胜利矿区为研究区,量化分析1986—2020年区域生态环境质量和生态累积效应的时空分布规律,以及主要人类活动的生态累积效应差异。结果表明:①SMAEEI适用于半干旱草原露天矿区,能客观呈现各地类生态环境质量高低顺序。35 a间研究区生态环境质量呈极显著下降趋势,且其空间差异显著减弱。露天矿场、城镇扩张区、锡林河湿地及北侧草地生态环境质量出现极显著、显著的退化趋势。②半干旱草原露天矿区生态累积效应定量评估模型能剔除气候因素对生态系统的耦合影响,分离并量化人类活动对矿区生态系统的累积效应,揭示累积的方向、程度和空间范围。35 a间研究区生态服务价值累积量(Change of Ecosystem Service Value Cumulant,COESVC)共减少1186157.03万元,出现负向生态累积效应,生态系统服务功能下降。高度、中度负向累积区集中在湿地和草地退化区、城镇区、露天矿场。③露天开采、城镇建设造成的单位面积负向生态累积效应最明显,前者在单位时间内带来的负向累积变化最剧烈,后者负向累积效应的局部影响程度和偏离度最大;放牧活动引起的负向生态累积效应影响范围最广、总量最大,但局部影响程度最小,生态系统服务功能较其余人类活动更稳定。研究成果可将矿区人类活动引起的生态环境实物量变动转化为价值量描述,为采用货币形式测算矿区生产生活行为的环境损害成本提供可行方法。

西部矿区地下水系统水化学过程及其采动激发效应

煤炭资源开采会破坏含水层结构,扰动地下水系统,产生新的水循环模式。作为煤炭保供生产重心的西部矿区,高强度、规模化的开采加剧了这一扰动,使水岩作用等水化学过程更加剧烈。其背后所蕴含的地下水系统水化学的煤矿开采激发效应,是关系到煤矿安全开采预测预报精度,以及绿色开采地下水环境保护的关键科学问题。鉴于此,以西部榆神矿区曹家滩煤矿为研究实例,利用水文地球化学的原理和方法,从“是什么”、“为什么”和“怎么变”的角度,开展激发效应结果、激发效应过程以及水化学演化趋势3个方面系统性的研究。结果发现:研究区的地下水可以被分为5个聚类,聚类1代表煤矿开采后井田西翼第四系与风化基岩含水层为主的浅层地下水,聚类2代表开采前后地下水的混合,聚类3代表开采前的地下水,聚类4和聚类5主要代表开采后的延安组地下水;煤矿开采后,直罗组、延安组第4段和第5段含水层水样中HCO_(3)–Ca和HCO_(3)–Mg占比上升,井田西翼开采后的浅层地下水水质整体最优,各含水层水质有向好演变的趋势且对煤矿开采的响应不敏感;研究区地下水整体受控于阳离子交替吸附作用,煤矿开采前延安组第4段及以上含水层地下水受控于碳酸盐岩和硅酸盐岩的溶解作用;煤矿开采后的井田西翼浅层地下水受控于碳酸盐岩的溶解作用,直罗组、延安组第4段和第5段含水层地下水主要受控于硅酸盐岩的溶解和FeS2的氧化作用,延安组第1~3段含水层地下水主要受控于蒸发盐的溶解作用;煤矿开采加速了地下水的循环速度、加强了含水层间的水力联系,由此产生的稀释作用与矿井水处理后综合利用的措施是延安组第4段及以上各含水层水化学特征和水质演化的原因;未来应当继续做好矿井水处理后综合利用的工作,并注意直罗组和延安组第5段地下水特征有向浅层地下水演变的趋势,避免今后的涌水水源结果产生误判。

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。

多种物探方法在昌吉硫磺沟地区煤田火烧区勘查中的应用研究

煤层自燃不仅影响周边生态环境,也存在较大的安全隐患。以昌吉硫磺沟地区为例,根据煤层自燃所产生的物理化学变化与周围岩石产生的物性差异,运用无人机红外成像、无人机航空磁测和自然电位法开展勘查,通过对三种方法的成果分析与解译,圈定煤田火烧区的范围,为后期治理等工作提供基础资料。

淮南阜东矿区二叠系砂岩高盐地下水低硫酸盐特征及成因机制

矿区地下水水文地球化学研究对矿井水防治和水资源综合利用具有重要意义。针对安徽淮南煤田阜东矿区二叠系砂岩水低硫酸盐问题,通过水样采集测试,采用多元统计方法,结合水文地质条件分析和硫氧同位素技术,研究砂岩水水化学特征、水-岩作用以及低硫酸盐成因。结果表明:研究区二叠系砂岩水呈弱碱性,TDS平均值为1842.35 mg/L,属于微咸水,水化学类型主要为Cl-Na型、HCO_(3)-Na型和Cl·HCO_(3)-Na型。SO_(4)^(2-)平均质量浓度为37.48 mg/L,明显低于淮南煤田东部潘谢矿区和淮北煤田二叠系砂岩水。主要水-岩作用为蒸发岩(氯盐岩和硫酸盐岩)和硅酸盐岩矿物溶解,存在阳离子交替吸附作用。由于边界阻水断层切割,二叠系砂岩含水层四周均为相对隔水边界,且埋藏较深,富水性弱,水动力条件较差,形成了一个封闭–半封闭的水文地质单元,具有较强的硫酸盐还原环境,有利于硫酸盐细菌还原,脱硫酸作用明显,导致δ^(34)S升高,砂岩水硫酸盐含量偏低。研究成果可为类似条件矿区涌突水水源识别提供依据。

淮南煤田潘集外围地区下二叠统泥页岩储层矿物特征研究

【目的】研究淮南煤田煤系下二叠统泥页岩的矿物组成和页岩气储集层物性,评价淮南煤田不同矿物对页岩气储层的影响。【方法】以淮南煤田潘集外围地区下二叠统上石盒子组、下石盒子组和山西组泥页岩为研究对象,通过X射线衍射实验,探究不同组成成分对页岩气储层的影响。【结果】结果表明:研究区泥页岩矿物组成以脆性矿物和黏土矿物为主,其中脆性矿物中石英占90%以上,其次含少量钾长石和钠长石,黏土矿物以高岭石和伊/蒙混层为主,少量绿泥石和伊利石。【结论】黏土矿物有利于页岩气吸附,研究区石英等脆性矿物含量相对较低,应采取合适的压裂技术进行开采。

宁东煤田枯竭油层回注存储高矿化度矿井水技术思路

宁东煤田地处我国西北干旱-半干旱区,是我国批准建设的14个亿吨级大型煤炭基地之一,目前存在高矿化度矿井水量大、处理技术成熟但成本高、综合利用率低等问题。为实现宁东煤田高矿化度矿井水的低成本资源化回注存储和水文生态环境保护,结合宁东煤田13座煤矿矿井水矿化度高的典型特征,因地制宜地提出在煤油资源重叠区,利用枯竭油层回注存储高矿化度矿井水这种宝贵的非常规水资源的技术思路,即利用枯竭油层孔-裂隙双重结构中储水空间、油田关停初期地层压力亏空和废弃油井/注水井低成本处置高矿化度矿井水经资源化利用后的余量水;系统阐述枯竭油层选择、回注工艺、储水潜力、预处理水质要求和环境的可行性;凝练出基础理论、法律法规政策和实时监测监管的研究展望。结果表明,提出的枯竭油层回注存储技术具有可行性,可实现宁东煤田高矿化度矿井水的低成本资源化处置,“如何精细刻画注水渗流过程”是回注处置技术瓶颈问题,科学实质是高矿化度矿井水-砂岩耦合化学作用下孔裂隙介尺度的枯竭油层注水渗流演化机理。同时,相关法律法规政策和实时监测监管方面亟需完善,以保障枯竭油层回注存储技术的顺利实施。研究旨在为高矿化度矿井水资源化回注存储提供新思路,为煤油气资源开发中二次水资源保护提供参考。

新疆吐哈煤田急倾斜煤层火区精准勘查技术研究——以吐鲁番221团煤矿为例

新疆煤田火区是我国乃至世界上最大的煤田火区,煤火不仅消耗掉大量煤炭资源,同时其燃烧后释放的有毒有害气体也对大气环境造成了严重污染,对国土资源也造成了严重的破坏,极大的影响了当地经济、社会与生态的发展。因此精准勘查火区范围对治理煤田火区具有重要意义。由于各个火区所处的煤田地质条件并不一致,且发火影响因素有差异,所以目前针对火区的勘查手段并没有统一的执行标准,同时通过单一的勘查手段并不能完全准确查明煤田火区的燃烧状况,而为了提高勘测精准程度就需要使用更多的勘查手段,这便使得勘查成本大幅提升。为了平衡好勘查精准程度与勘查成本,本次针对新疆吐哈煤田急倾斜煤层火区采用了综合勘查手段,通过实践研究表明,在控制成本的基础上,本次采用的综合勘查手段有很高的准确度和可靠性,为其他具有类似地质与开采技术条件的煤田火区精准勘查提供了良好的借鉴。

攀枝花宝鼎煤田露头大面积火区探测成果分析

科学分析煤田露头火区燃烧界限,准确判断其影响范围和危害程度,有利于提出有效的治理措施。攀枝花市运用高分遥感、无人机航测等先进技术手段和设备,对宝鼎煤田大面积火区开展了详实的探测,探测出39个火区点位的燃烧状况,形成44.85 km^(2)的光学影像、10.30 km^(2)的热红外影像图和250 km^(2)的遥感影像图,圈定露头火区面积为17.43万m^(2),划定影响范围面积为1285.19万m^(2)。根据探测结果,分析了火区特点、变迁原因及危害,提出按照“分级防治、逐步推进、综合管控”的原则,采取火情监测、火源探测、注水降温、注浆灭火、高温区煤体剥离、黄土覆盖等综合防治措施,推进火区治理进度,为宝鼎煤田露头大面积火区治理提供了基础资料和决策依据。

二连盆地巴彦宝力格煤田伊敏组低煤阶煤层气成藏条件及有利区预测

为了明确二连盆地巴彦宝力格煤田伊敏组煤层气资源潜力,在伊敏组煤层发育及含气性分析基础上,对沉积环境、煤层厚度、构造特征、储层物性、盖层封闭能力及水文地质条件等煤层气成藏条件进行了系统剖析。结果表明:巴彦宝力格煤田伊敏组煤层的煤岩组分以暗煤为主,最大镜质体反射率为0.38%~0.46%,属于褐煤-长焰煤;伊敏组主力煤层为2#、3#、4#、4-1#煤,煤层分布广泛,结构简单,平均厚度为21.33 m,具备丰富的生气物质基础;煤层含气量差异较大,平均含气量为0.79~1.57 m^(3)/t,其中4#煤层含气量最高,4-1#煤层含气性最差;煤层沉积环境以扇三角洲及滨浅湖湖沼相为主,有利于形成广覆式中厚煤层;盆地构造形态简单,煤层主要赋存于向斜,受断裂影响较小,并且顶底板多为分布稳定的厚层泥岩;煤系含水层处于承压水封闭环境,为煤层气赋存提供了良好的保存条件;伊敏组煤层气有利勘探区主要位于中部的巴彦宝力格向斜轴部地区及东北部的五间房向斜轴部地区。研究成果对伊敏组及类似条件的低煤阶煤层气勘探开发具有指导意义。

高温煤岩体电性特征及地球物理数值模拟研究

为指导煤田火区地球物理勘探技术,判断煤火发展的阶段,精准识别隐蔽火区边界,通过分析岩石的导电机理、狭义的煤岩体电性特征,有针对性地展开煤及煤围岩高温电性研究。通过实验测试煤岩体在不同温度下的电阻值,总结出煤岩石电阻率随温度的变化规律及其影响机制;以数值模拟方法为手段,建立煤田火区地电模型并开展瞬变电磁(TEM)正反演计算。结果表明:煤的电阻率随着温度升高而减小,在高温阶段煤的含碳量是影响其电阻率的主导因素;干燥煤围岩的电阻率随温度的升高而降低,热动力条件下自由移动的载流子数量是影响其电阻率的主导因素;高温煤比高温围岩引起的瞬变电磁异常响应幅值大得多,瞬变电磁中心回线装置对于高温火区的耦合效果最佳,火区埋深越浅电性异常效果越明显。