辛安煤矿1402工作面临空窄煤柱采掘响应及动态加固

随着我国煤炭资源去产能整合煤矿的增多,复采工作面临空窄煤柱采动失稳问题日益凸显,已严重制约矿井安全高效生产。为此,针对辛安煤矿复采1402工作面辅运巷道5号钻场临空窄煤柱稳定性控制的工程难题,运用数值模拟与理论分析相结合的方法,探究5号钻场临空窄煤柱稳定性采掘扰动响应特征,提出5号钻场临空窄煤柱动态注浆加固技术方案并开展现场应用和效果检验。研究结果表明:1402工作面辅运巷道掘进对5号钻场临空窄煤柱稳定性影响较小;在1402工作面回采期间,距5号钻场18~6 m范围,临空窄煤柱集中垂直应力由非对称马鞍形分布逐渐过渡为拱形分布;距5号钻场6 m时,临空窄煤柱承载叠加垂直应力超过煤体强度,塑性区完全贯通,极易破坏失稳;现场采用MP364型注浆材料及专用注浆设备对5号钻场临空窄煤柱前后5 m区域进行加固,动态注浆始终超前工作面10 m,通过深孔窥视和气体监测手段验证临空窄煤柱良好的封堵固化效果,保障了工作面安全回采,为我国整合矿井类似条件下煤柱稳定性控制提供借鉴和参考。移动阅读      

Subsidence prediction method of solid backfilling mining with different filling ratios under thick unconsolidated layers

Solid backfill mining for coal pillar recovery in industrial squares has to ensure that the mine infrastructure, such as the shafts and substations, is not degraded or has its utility impaired by that mining. At the same time, it is important to recover as much coal as possible. As a result, it is necessary to predict mining subsidence during solid backfilling mining of coal pillars in industrial squares and to optimize the design of the working faces. At the Baishan coal mine in Anhiu province, China, there are thick layers of unconsolidated overburden above the coal seam so it is not appropriate to use the surface subsidence prediction method of equivalent mining height to predict subsidence during the mining of the coal pillars there. In order to find a reasonable coal pillar recovery scheme for the Baishan mine, a numerical simulation method is used to determine the relationships between the compression ratio of the backfilling material and the surface subsidence prediction parameters. Research was done to determine the appropriate parameters, and based on the final prediction parameters and taking the mandated protection standards for buildings and structures into account, surface subsidence is predicted and a backfill mining scheme for pillar recovery is proposed. The results show that of the six mining schemes considered, scheme 5 is the best scheme for coal pillar recovery in the industrial square at the Baishan mine. The research results are significant for similar mines with thick unconsolidated overburden anywhere in the world.     

黄土丘陵区房柱式开采地表塌陷特征及机理分析——以陕北府谷县新民镇小煤矿为例

通过对陕北府谷县新民镇小煤矿采煤地表大面积塌陷的调查和分析,总结出黄土丘陵区房柱式开采地表的塌陷特征,并以西岔沟煤矿房柱式开采为例,对其两种参数顶板岩梁应力、煤柱载荷、煤柱强度进行分析及对比,结果表明合理设计煤柱和煤房尺寸可以防止采煤地表大面积塌陷。     

基于巨厚岩层-煤柱协同变形的煤柱稳定性

采前煤柱稳定性研究是工作面冲击危险性评估和开采方案设计的关键。以山东某矿深井巨厚砾岩条件工作面开采遗留煤柱为背景,采用案例调研、理论分析、数值模拟和工程实践等方法,对巨厚岩层-煤柱协同变形机制及其煤柱稳定性进行了研究,建立了巨厚岩层-煤柱协同变形的简化力学模型,探讨了引起煤柱变形的主要应力来源和变形形式,推导了在协同变形条件下煤柱的应力-应变关系。以此为基础,综合煤柱煤体应力、围岩稳定性和变形特征等条件,提出了煤柱整体失稳的力学判据。研究结果表明：巨厚岩层-煤柱失稳诱发冲击与煤柱的位置、尺寸和上覆岩层运动或变形关系密切,上覆岩层运动或变形是诱发煤柱失稳的动力因素;巨厚岩层-煤柱的变形主要包括受集中力F压迫的协同挠曲压缩变形和受集中力G作用的重力沉降变形,二者保持内在协调性;巨厚岩层下煤柱整体失稳的工程判据为煤柱煤体平均支承应力p超过其平均极限支承强度Rc（p≥Rc）;评估得到遗留的50 m煤柱具有强冲击危险性,并通过优化开采设计,取得了良好的效果。该研究成果对相似条件煤柱留设及其稳定性分析具有参考意义。     

泾河下综放开采隔离煤柱对覆岩破坏控制作用的物理模拟

根据地质资料,分析了下沟煤矿泾河下特厚煤层大面积综放开采的地质特点,为实现水体下安全回采,确定了在各工作面间留设一定宽度隔离煤柱的开采方案。通过相似材料模拟试验,分析了改本区地质条件下各综放工作面间留设一定宽度隔离煤柱对覆岩破坏的影响。研究证实,隔离煤柱对覆岩破坏起到有效的控制作用。根据试验得出的单工作面最大裂采比,通过最小防水安全煤岩柱垂高的计算,认为地质条件满足泾河下安全回采的要求。且研究成果成功指导了5个工作面安全回采,可为该区及类似条件其他矿井的开采提供参考     

Stability of goaf-side entry driving in 800-m-deep island longwall coal face in underground coal mine

Goaf-side entry driving in underground coal mines could greatly improve coal recovery rates. However, it becomes more difficult to maintain stability, especially in deep coal mines. Pillar width plays a pivotal role in the stability of goaf-side entry driving. To obtain a reasonable and appropriate narrow pillar width, theoretical calculations of the widths of mining-damaged zone and limit equilibrium zone in the pillar are derived according to limit equilibrium theory. Based on the stability issues of goaf-side entry driving in the first island longwall coal face (LCF) at a depth of 800 m below the surface in Guqiao Coal Mine in China, a numerical model is established by FLAC software to analyze the stability of the surrounding rock of goaf-side entry driving during excavation, using various coal pillar widths and support schemes. The results obtained from theoretical calculations, numerical simulation, and engineering practice indicate that an 8-m-wide coal pillar is relatively reasonable, appropriate, and feasible. Field measurements show that deformations of the surrounding rock could be efficiently controlled 31 days after the support schemes were implemented in goaf-side entry driving with an 8-m-wide narrow pillar along the adjacent goaf side with a compaction duration of 10 months. The mining influence range of the overlying LCF on the stability of goaf-side entry driving is found to be the area from 50 m ahead of the LCF to 70 m behind the LCF as it passes over the measurement point.     

矿井初步设计中边界防隔水煤岩柱留设探讨

针对一些矿井初步设计中留设边界防隔水煤岩柱不合理而引发矿井老空水矿难的现实,探讨了影响矿井间边界防隔水煤岩柱安全稳定性的因素,提出应充分考虑煤岩柱受覆岩应力破坏变形、覆岩受采动影响产生岩移破坏等,综合分析计算煤柱有效稳定性弹性核区宽度、覆岩导水裂缝带上限岩柱宽度及其抗静水压能力等,择优选取留设矿井边界防隔水煤岩柱。以济宁煤田济宁二矿与三矿边界煤柱的留设为例,计算其边界煤柱留设尺寸为99.56m,较原设计的40m有较大出入,据此对两矿井边界隔离煤柱进行了相应调整,确保了矿井的安全生产。该方法也可用于矿井留设采区、区段隔离煤柱的计算。     

Improving stress environment in development entries through an alternate longwall mining layout

Most coal mines in China use the longwall mining system. High stresses are frequently encountered around development entries at deep mines. This paper presents an alternate longwall mining layout for thick coal seams to minimize ground control problems. In a conventional longwall panel layout, development entries on both ends of the panel are located along the floor, and a coal pillar (chain pillar) is left between adjacent panels to ensure stability. Gateroads on either end of a longwall panel using the layout proposed in this paper are located at different vertical levels within a thick coal seam or in a geologically split coal seam for improved stability. The headgate entry/ies are driven along the floor while the tailgate entry/ies are driven along the roof. Therefore, a longwall face has a gradually elevated or curved section on one end of the panel. For the adjacent panel, the development entry may be located directly below the development entry of the previous panel or may be offset horizontally with respect to it. Based on physical and numerical modeling approaches, it is demonstrated that the stress environment for development entries employing the longwall layout is significantly improved; ground control problems are therefore minimized.     

Application of artificial intelligence techniques for predicting the flyrock distance caused by blasting operation

Flyrock arising from blasting operations is one of the crucial and complex problems in mining industry and its prediction plays an important role in the minimization of related hazards. In past years, various empirical methods were developed for the prediction of flyrock distance using statistical analysis techniques, which have very low predictive capacity. Artificial intelligence (AI) techniques are now being used as alternate statistical techniques. In this paper, two predictive models were developed by using AI techniques to predict flyrock distance in Sungun copper mine of Iran. One of the models employed artificial neural network (ANN), and another, fuzzy logic. The results showed that both models were useful and efficient whereas the fuzzy model exhibited high performance than ANN model for predicting flyrock distance. The performance of the models showed that the AI is a good tool for minimizing the uncertainties in the blasting operations.     

Geological and geotechnical aspects of underground coal mining methods within Australia

About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate.     

矿柱稳定性影响因素敏感性分析及其应用研究

为研究矿柱稳定性影响因素的敏感程度,以招金大尹格庄金矿为研究背景,从矿柱载荷、强度、失稳形式及影响因素确定四方面推导出两种矿柱形式的安全系数计算公式,设计采用6因素5水平正交试验对矿柱稳定性影响因素敏感性进行分析,并研究主要影响因素与矿柱安全系数之间的函数关系。研究表明,矿柱宽度、矿体开采深度和矿房宽度3个主要因素对矿柱稳定性影响程度是最为剧烈的;矿柱安全系数随着矿柱宽度地增加呈指数形式递增且递增速率不断加大,随矿体开采深度地增加呈幂函数形式递减且递减速率逐渐变缓,随矿房宽度地增加呈负指数形式递减且降低速率逐渐变慢。利用DPS和Matlab建立的矿柱安全系数回归方程得出保证安全生产的合理矿柱尺寸,矿房宽度应不超过8 m,布置条形矿柱宽度应不小于3.6 m,布置方形矿柱宽度应不小于5.9 m。结合采场矿柱布置实际,应用效果较为理想,可为下中段矿体回采矿块布置提供较好的依据。     

Assessment of ground subsidence hazard near an abandoned underground coal mine using GIS

This study constructs a hazard map for ground subsidence around abandoned underground coal mines (AUCMs) at Samcheok City in Korea using a probability (frequency ratio) model, a statistical (logistic regression) model, and a Geographic Information System (GIS). To evaluate the factors related to ground subsidence, an image database was constructed from a topographical map, geological map, mining tunnel map, Global Positioning System (GPS) data, land use map, lineaments, digital elevation model (DEM) data, and borehole data. An attribute database was also constructed from field investigations and reports on the existing ground subsidence areas at the study site. Nine major factors causing ground subsidence were extracted from the probability analysis of the existing ground subsidence area: (1) depth of drift; (2) DEM and slope gradient; (3) groundwater level, permeability, and rock mass rating (RMR); (4) lineaments and geology; and (5) land use. The frequency ratio and logistic regression models were applied to determine each factor’s rating, and the ratings were overlain for ground subsidence hazard mapping. The ground subsidence hazard map was then verified and compared with existing subsidence areas. The verification results showed that the logistic regression model (accuracy of 95.01%) is better in prediction than the frequency ratio model (accuracy of 93.29%). The verification results showed sufficient agreement between the hazard map and the existing data on ground subsidence area. Analysis of ground subsidence with the frequency ratio and logistic regression models suggests that quantitative analysis of ground subsidence near AUCMs is possible.     

大采高综放面区段煤柱合理留设研究

侧向支承压力分布、资源回收率以及煤柱和巷道的稳定性是大采高综放面区段煤柱宽度留设要兼顾的因素,为了确定大采高综放面区段煤柱宽度,以某矿8103面为工程背景,首先,采用理论计算和现场应力监测等方法确定大采高综放工作面倾向支承压力分布规律,得出应力降低区宽度约为8 m,原岩应力区为巷帮侧28 m外。其次,采用工程类比方法确定大采高综放工作面巷帮外侧煤体严重破裂区宽度约为4 m。最后,采用FLAC3D数值软件分析了下区段工作面回采时窄煤柱（6、8 m）和宽煤柱（28、30 m）的应力场、位移场及塑性区特征,获得不同煤柱宽度时巷道和煤柱力学特征。研究表明：当煤柱宽度6 m和8 m时,在采动支承压力下煤柱几乎无承载能力,且巷道变形量较大;当煤柱宽度28 m和30 m时,在采动支承压力下煤柱中央仍有一定的弹性核,煤柱保持稳定且巷道变形量较小。综合考虑资源回收、巷道稳定性、次生灾害控制等因素,确定大采高综放工作面区段煤柱宽度为28 m。     

Research and application of roadway backfill coal mining technology in western coal mining area

In China’s western coal mining area, the traditional room mining technology is facing coal pillar instability, mine earthquake, large-area roof subsidence in the goaf, surface subsidence, water and soil loss, vegetation deterioration, and other environmental problems. To solve the aforementioned problems and to improve coal recovery, the roadway backfill coal mining (RBCM) method was proposed as a solution and its technical principle and key equipment were presented in this paper. In addition, the microstructure and mechanical behavior (strain-stress relation in confined compressive test) of aeolian sand and loess backfill materials were studied for a rational backfill design for underground mines. Further, coal pillar stress, plastic zone change, and surface deformation of the RBCM schemes were studied using the FLAC^3D numerical simulation software, and a reasonable mining scheme of “mining 7 m and leaving 3 m” was determined. The engineering application in Changxing Coal Mine shows that the RBCM method with loess and aeolian sand as backfill materials allows a stable recovery of coal pillars with a recovery ratio of more than 70 %. The maximum accumulated surface subsidence and the maximum horizontal deformation were measured to be 15 mm and 0.8 mm/m respectively, indicating that the targeted backfilling effect can help protect the environment and also control surface subsidence.     

Analysis of sinkhole occurrences over abandoned mines using fuzzy reasoning: a case study

In Korea most of the old mine workings were worked with room and pillar method or sublevel caving method and today they possess great possibility of surface subsidence especially for shallow depth mines. In most of the cases, mine roadways, rooms and pillars are irregular in shape and information about the local geology is uncertain. For these reasons, it is difficult to standardize the estimating method of subsidence especially sinkhole type over abandoned mine area. This paper describes the application procedure for the fuzzy reasoning techniques to analyze the possibility of sinkhole occurrences over abandoned mines. This technique is implemented in software which can simplify the analysis procedure and present the possibility of sinkhole subsidence without having precise information about local geological/mining conditions. This technique has been applied to forecast sinkhole possibilities at Bonghwa site where a massive sinkhole has already been occurred.     

模糊综合评判模型在隐伏矿定位预测中的应用

对于隐伏矿的定位预测,恰当的描述与处理不精确、非线性的控矿因素信息一直是困扰找矿工作者的难题。模糊数学用隶属函数来刻画元素对集合属于程度的连续过渡性,将经典集合的二值逻辑{0,1}扩展为[0,1]区间内的连续值逻辑。基于以上认识,本文利用模糊数学方法,结合AHP(层次分析法),建立了模糊层次综合评判模型,并用于对个旧矿区阿西寨测区5个异常区的综合评价研究。应用实例表明,该方法有效可行,能够给出合理的总体评价结论。     

Floor design in underground coal mines

Summary Floor failure and excessive heave in underground coal mines can jeopardize the stability of the whole structure, including the roof and pillars, due to differential settlements and redistribution of stress concentrations. Besides, floor failure is detrimental to haulageway operation and can lead to unacceptable conditions of high deformation. Thus, the design of any underground opening must consider roof/pillar and floor as one structural system.This paper presents guidelines for the design of mine floors, including the necessary field and laboratory investigations and the determination of the bearing capacity of floor strata. The design methodology is based essentially on a modified Hoek-Brown rock mass strength criterion. The main modifications are the introduction of the concept of the point of critical energy release to account for the long term strength, the inclusion of tensile strength and the adoption of a lithostatic state of stress in the rock mass. The determination of the dimensionless parametersm ands result from correlations with the RMR (rock mass rating) of the Geomechanics Clasification. Nine case histories, both in longwall and room and pillar coal mining, were analyzed with the proposed methodology.     

山西省废弃矿井煤层气地面钻井开发关键问题与对策

随着我国煤炭去产能政策的有力实施,一批资源枯竭及产能落后矿井将陆续关停废弃。废弃矿井仍赋存着大量的煤层气资源,其开发利用是实现煤炭产业清洁安全高效低碳发展、促进煤矿安全生产、优化能源结构、实现温室气体减排等方面的重要举措。基于山西省煤基重点科技攻关(煤层气产业链)项目相关研究,系统阐述了废弃矿井煤层气开发面临着资源量评价不准、钻进体系不健全、井上下联合缺失等关键问题。针对这些问题提出以下几点对策:废弃矿井精准地质探测是采空区地面钻井轨迹设计的重要依据,尤其是炮采等落后采煤工艺的废弃矿井,地球物理勘探精度应达到米级才能有效降低钻遇煤柱风险;优选废弃矿井煤层气地面“L”型钻井思路,即选采空区周边一定距离的保安煤柱作为L型井位,并配套特殊钻进工艺;煤矿企业应将废弃矿井资源开发利用纳入煤矿全生命周期规划,尤其是矿井废弃前应确保煤层气抽采通道畅通,以实现煤层气井“一井多用”的新型井上下联合开采模式,提高废弃矿井煤层气开发效率;采用防回火、各种传感器等装置,并对关键参数设置自动报警停机界限值,从而使废弃矿井煤层气地面开采工艺安全、高效;对不同浓度废弃矿井煤层气,需要采取相应的梯级利用模式,从而提高整体开发利用价值。以山西省废弃矿井为示范区,研究认识对推动全国煤矿区废弃矿井煤层气开发利用具有重要的指导和示范意义。      

Access tunnel convergence prediction in longwall coal mining

Summary The paper describes theoretical andin situ studies of tunnel deformation in longwall coal mining. It develops a method to predict tunnel convergence profiles from the faceline in longwall mining. The method accounts for the effect of panel width, extracted seam height, deformation moduli of the goaf material and coal pillar, depth of cover,in situ structural defects, tunnel shape and tunnel size in addition to the strength characteristics of surrounding strata. The analytical technique has been validated by reference toin-situ deformation measurements in 26 face-access tunnels in Cape Breton Coalfield mines. Based on this method a series of vertical convergence profiles for different depths and extracted panel widths have been presented.     

Numerical Investigation of the Dynamic Mechanical State of a Coal Pillar During Longwall Mining Panel Extraction

This study presents a numerical investigation on the dynamic mechanical state of a coal pillar and the assessment of the coal bump risk during extraction using the longwall mining method. The present research indicates that there is an intact core, even when the peak pillar strength has been exceeded under uniaxial compression. This central portion of the coal pillar plays a significant role in its loading capacity. In this study, the intact core of the coal pillar is defined as an elastic core. Based on the geological conditions of a typical longwall panel from the Tangshan coal mine in the City of Tangshan, China, a numerical fast Lagrangian analysis of continua in three dimensions (FLAC^3D) model was created to understand the relationship between the volume of the elastic core in a coal pillar and the vertical stress, which is considered to be an important precursor to the development of a coal bump. The numerical results suggest that, the wider the coal pillar, the greater the volume of the elastic core. Therefore, a coal pillar with large width may form a large elastic core as the panel is mined, and the vertical stress is expected to be greater in magnitude. Because of the high stresses and the associated stored elastic energy, the risk of coal bumps in a coal pillar with large width is greater than for a coal pillar with small width. The results of the model also predict that the peak abutment stress occurs near the intersection between the mining face and the roadways at a distance of 7.5 m from the mining face. It is revealed that the bump-prone zones around the longwall panel are within 7–10 m ahead of the mining face and near the edge of the roadway during panel extraction.