Analysis of the Risk of Water Breakout in the Bottom Plate of High-Intensity Mining of Extra-Thick Coal Seams

In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site monitoring means combining borehole peeping and microseismic monitoring, combined with the theoretical analysis to analyze the danger of water breakout in the bottom plate. The results show that: 1) the theoretically calculated maximum damage depth of the bottom plate is 27.5 m, and its layer is located above the Austrian ash aquifer, which has the danger of water breakout;2) the drill hole peeping at the bottom plate of the working face shows that the depth of the bottom plate fissure development reaches 26 m, and the integrity of the water barrier layer has been damaged, so there is the risk of water breakout;3) for the microseismic monitoring of the anomalous area, the bottom plate of the return air downstream channel occurs in the field with a one-week lag, which shows that microseismic monitoring events may reflect the water breakout of the underground. This shows that the microseismic monitoring events can reflect the changes of the underground flow field, which can provide a reference basis for the early warning of water breakout. The research results can provide reference for the prediction of sudden water hazard.

Behaviors of overlying strata in extra-thick coal seams using top-coalcaving method

Accidents such as support failure and excessive deformation of roadways due to drastic changes in strata behaviors are frequently reported when mining the extra-thick coal seams Nos.3e5 in Datong coal mine with top-coal caving method,which significantly hampers the mine's normal production.To understand the mechanism of strata failure,this paper presented a structure evolution model with respect to strata behaviors.Then the behaviors of strata overlying the extra-thick coal seams were studied with the combined method of theoretical analysis,physical simulation,and field measurement.The results show that the key strata,which are usually thick-hard strata,play an important role in overlying movement and may influence the mining-induced strata behaviors in the working face using top-coal caving method.The structural model of far-field key strata presents a 'masonry beam' type structure when'horizontal O-X' breakage type happens.The rotational motion of the block imposed radial compressive stress on the surrounding rock mass of the roadway.This can induce excessive deformation of roadway near the goaf.Besides,this paper proposed a pre-control technology for the hard roof based on fracture holes and underground roof pre-splitting.It could effectively reduce stress concentration and release the accumulated energy of the strata,when mining underground coal resources with top-coal caving method.

Prediction of upper limit position of bedding separation overlying a coal roadway within an extra-thick coal seam

Failure of the surrounding rock around a roadway induced by roof separation is one major type of underground roof-fall accidents.This failure can especially be commonly-seen in a bottom-driven roadway within an extra-thick coal seam("bottom-driven roadway"is used throughout for ease of reference),containing weak partings in their roof coal seams.To determine the upper limit position of the roof interlayer separation is the primary premise for roof control.In this study,a mechanical model for predicting the interlayer separation overlying a bottom-driven roadway within an extra-thick coal seam was established and used to deduce the vertical stress,and length,of the elastic,and plastic zones in the rock strata above the wall of the roadway as well as the formulae for calculating the deflection in different regions of rock strata under bearing stress.Also,an approach was proposed,calculating the stratum load,deflection,and limiting span of the upper limit position of the interlayer separation in a thick coal seam.Based on the key strata control theory and its influence of bedding separation,a set of methods judging the upper limit position of the roof interlayer separation were constructed.In addition,the theoretical prediction and field monitoring for the upper limit position of interlayer separation were conducted in a typical roadway.The results obtained by these two methods are consistent,indicating that the methods proposed are conducive to improving roof control in a thick coal seam.

Numerical Study on an Applicable Underground Mining Method for Soft Extra-Thick Coal Seams in Thailand

The EGAT Mae Moh Mine is the largest open pit lignite mine in Thailand and it produces lignite about 16 million tons annually. In the near future, the pit limit of the mine will be reached and underground mine will then be developed through the open pit in the depth of 400 - 600 m from the surface. However, due to the challenges for underground mining such as poor geological conditions, extra thickness (20 - 30 m) of coal seams, and weak mechanical properties of coal seams and the surrounding rock, the success possibility of underground mining and an applicable underground mining method is being investigated at the present. The paper discusses the applicability of multi-slice bord-and-pillar method for the soft extra thick coal seams in the Mae Moh mine by means of numerical analyses using the 3D finite difference code “FLAC3D”.

Strata behavior in extra-thick coal seam mining with upward slicing backfilling technology

Based on the character of upward slicing backfilling mining and the condition of Gonggeyingzi coal mine in Inner Mongolia,this paper describes the studies of the strata behavior and the stress distribution in the process of backfilling mining in extra-thick coal seams.This was achieved by setting up and analyzing the elastic foundation beam model using the ABAQUS software.The results show that:(1) With the gradual mining of different slices,the roof appears to bend continuously but does not break.The vertical stress in the roof decreases and the decreasing amplitude reduces,while the tensile stress in the roof grows with the mining slices and the maximum tensile stress will not exceed the allowable tensile stress.(2) The front vertical stress at the working face exceeds the rear vertical stress and both show a trend of decrease with decreasing amplitude of decrease.(3) The slices mined early have more influence on the surrounding rock than the later ones.Similarly,the strata behavior experiences the same trend.The field measured data show that the roof does not break during the mining process,which is consistent with the conclusion.

复杂煤层组隧道围岩与支护结构施工力学行为

隧道开挖穿越倾斜煤系地层时,容易出现因围岩变形过大而导致的坍塌,严重时进而诱发瓦斯突出、爆炸等次生灾害发生。为保证富煤隧道安全高效施工,以天城坝隧道为背景工程,采用数值模拟软件FLAC^(3D)结合现场监测的方法,探究五种厚度下复杂煤层组的围岩变化规律以及施工工法的适用性。研究结果表明:①随着煤层厚度的增大,煤层组围岩变形均越来越大,变形在开挖步数50 m左右处达到峰值。②对比分析两种工法下五组煤层围岩变形量和初期支护应力,三台阶预留核心土法相较于三台阶法能有效降低围岩变形。③将三台阶预留核心土开挖模拟结果与现场实测数据对比,拱顶和仰拱数据差值率分别为5.69%和5.68%,均在允许范围内。这说明三台阶预留核心土法施工能有效控制隧道施工对洞周围岩的扰动,可保证复杂煤层组隧道的安全高效开挖。

Demonstration Project of Safe and Efficient Mining Operations in Extra-thick Coal Seam

Mineable coal reserves in thick and extra-thick seams account for 44% of the total deposit in China. Fullymechanized top-coal caving technology is a new mining method of safe and efficient underground operations in extra-thick seams in China. The development of fullymechanized top-coal caving technology in China, which was successfully applied in Face 8105 in Tashan Coal Mine, Datong, Shanxi, China, is analyzed in this paper.Studies on movement pattern of top-coal and roof from fully-mechanized top caving face in 14–20 m extra-thick seams have been carried out. A series of key technologies were successfully developed, including strata control technology, equipment for high-efficient and high-recovery top caving operations, and safety guarantee technology for low gas occurrence and high gas emission. As a result, the fully-mechanized top-coal caving Face 8105, with large mining height in Tashan Coal Mine, has achieved a recovery rate of 88.9% and an average equipment operation rate of 92.1%. With coal production of 10.84 Mt in 2011,the demonstration project is a technology and equipment breakthrough for fully-mechanized top-coal caving face in extra-thick coal seams with large mining height.

复杂地质条件下急斜厚煤层巷道变形特征

在急倾斜煤层的综放开采过程中,巷道变形与失稳对安全生产影响极为严重。乌鲁木齐矿区地质条件极为复杂,主采煤层均为急倾斜特厚煤层,地压活动强烈,煤岩接触带巷道局部变形、冒顶与底鼓严重,且有局部垮塌现象。通过对大洪沟矿+555B1～B6巷道围岩松动范围进行监测分析与评价,其巷道总体稳定性较好,因其处于煤带转折附近,地质构造复杂,煤层错位、松散、破碎。

开滦矿区复杂煤层综合机械化放顶煤开采技术

回顾了开滦(集团)有限责任公司复杂煤层综合机械化放顶煤开采的发展历程。介绍了放顶煤开采的3种类型,即一次采全厚放顶煤开采、预采顶分层网下放顶煤开采以及倾斜分段分层放顶煤开采。从中位放顶煤和低位放顶煤开采等方面分析了开滦集团公司在放顶煤开采技术上的探索、改革与发展过程以及在各个阶段所取得的成果,并着重阐述了特厚煤层低位放顶煤、厚煤层轻型支架放顶煤、急倾斜厚煤层微型支架放顶煤和大倾角特厚煤层放顶煤等低位放顶煤开采技术的结构与技术特征。最后介绍了开滦集团公司在生产过程中所积累的放顶煤开采工艺参数的选择以及放顶煤安全开采的影响因素等方面的研究成果。

赵庄矿软煤层大采高煤壁片帮主要影响因素研究

针对赵庄矿复杂地质条件下软煤层大采高工作面煤壁片帮严重的问题,通过对比3个盘区不同工作面煤壁片帮情况,对片帮机理和影响煤壁片帮的主要因素进行综合分析。找到工作面煤壁片帮的主要自然因素为3#煤层松软,节理裂隙发育,加之地质构造复杂,受岩层产状影响工作面倾斜仰采区域较多。支架初撑力、采高和工作面推进速度是影响工作面煤壁片帮的主要生产技术因素。对上述原因,提出了相关改进措施,确保了煤矿安全生产。

卸压开采抽采瓦斯理论及煤与瓦斯共采技术体系

针对低透气性、高吸附性、高瓦斯煤层群安全高效开采技术难题,以淮南矿区为主要试验研究基地,应用岩石力学、岩层移动、"O"形圈、瓦斯流动等理论,研究卸压开采采场内岩层移动及应力场分布规律、裂隙场演化及分布规律、卸压瓦斯富集区及运移规律等科学规律.针对不同煤(岩)层和瓦斯地质条件,探索出卸压开采抽采瓦斯理论,建立了卸压开采抽采瓦斯、煤与瓦斯共采技术体系.创新了低透气性、高瓦斯煤层群安全高效开采矿井设计理论,解决了煤与瓦斯共采重大工程技术难题.

复杂地质条件近水平煤层石门揭煤瓦斯治理技术

针对复杂地质条件近水平煤层的赋存特点,提出了控制层位、煤层预抽、边掘边抽、金属骨架、排放卸压5步复杂地质条件近水平石门揭煤方法;该方法在祁南煤矿南大巷石门揭煤中得到了应用,并取得了良好的效果。

复杂特厚煤层综放工作面煤柱应力分布规律研究

为了掌握塔山煤矿3—5号煤层综放面煤柱应力分布及巷道变形规律，在深入调研目前煤柱压力显现情况的基础上，通过在2个综采放顶煤工作面回风巷布置应力观测区，在测区内安装GYW25型钻孔应力传感器和KJ216-F2本安型监测分站，动态监测煤柱内应力变化，同时进行了巷道围岩变形观测。观测分析结果表明：在8208工作面回采期间，煤柱应力波动较大，峰值位置位于距8210工作面一侧25m，距8208工作面一侧13m附近；在留设38m区段煤柱的情况下，8208工作面前方100m范围内回风巷顶底板累计移近量达到1000～1400mm，两帮达到600～1000mm；在回采与掘巷相向施工条件下，38m煤柱是安全的、合理的；从8210工作面回风巷煤柱应力峰值位置分析，可以将煤柱减小到30～35m。

采煤机滚筒截割复杂煤层的突变分析

为研究采煤机滚筒截割复杂煤层时载荷的变化规律,在构造复杂煤层结构形式的基础上进行了实验研究。根据实验载荷建立了截割载荷的本构模型,并建立了不同结构形式煤层的力学模型。同时,根据井下实际工况建立了滚筒截煤的力学模型,基于突变理论建立了截割过程的尖点突变力学模型,获得了滚筒截煤的刚度和能量条件。分析结果表明:煤层的阻侵刚度需大于采煤机牵引系统的刚度,否则采煤机将出现强烈的振动,使得传动系统损坏;同时,煤层破碎所需的能量应不大于截割滚筒的能量释放率,否则采煤机滚筒将出现堵转现象,严重时截割电机将被损害。

清水营煤矿大倾角煤层赋存特征综合分析

全面了解复杂条件下大倾角煤层赋存特征是实现大采高开采安全开采的前提。清水营煤矿大采高工作面岩体节理与裂隙发育,富含水。基于现场地球物理勘探的基础上,完成了矿区工程地质特征的综合调查,分析了岩层岩性、构造、地震物理特征以及煤岩的物理/力学参数,为大采高安全开采提供了地质保障。

地形复杂地区煤层地温等值线绘制方法初探

查明井田内的地温分布状况是煤田地质勘探的重要任务之一,特别是石灰岩较发育地区及地形切割严重地区,由于岩溶较发育,形成的喀斯特峰丛地貌对煤层埋藏深度影响较大,煤层埋深无规律变化是影响煤层地温不均匀的主要因素。查明煤层地温的分布情况是龙永煤田生产建设中的一个重要问题。探讨了福建山区地貌与喀斯特峰丛地貌条件下的煤层底板地温等值线绘制方法。

淮南矿区高瓦斯煤层群深井开拓实践

淮南矿区近年来采取分区开拓、分区通风、分水平开拓、分水平通风开拓方式,使建井工期、达产工期大为缩短,安全生产状况大为改观,取得了经济效益和安全效益双丰收,为复杂地质条件高瓦斯煤层群深井开采提供了必要的技术储备和借鉴经验。

大倾角极复杂煤层采煤方法研究

黄兰矿区属典型的急倾斜"鸡窝状"极复杂煤层,煤层在走向和倾向上均变化很大,在厚度和倾角上也变化很大,赋存极不稳定。煤层一般在走向或倾向方向上30m内就会有变化,而且相对稳定的主采煤层也很难有在100m内不发生变化的情况。针对此复杂条件,提出"先探后采,采探结合"的开采理念,通过优化巷道布置及通风路线优化设计,开发出三种适于这类大倾角极不稳定"鸡窝状"煤层的开采方法,解决了此条件下大倾角煤层的安全开采问题,为具有南方特色的煤矿开辟了新路子。

湖南煤矿复杂煤层条件下实施综采对策

以湖南煤矿实施综合机械化开采工艺为工程背景,从煤矿开采技术条件、中小型地质构造探测技术、复杂煤层回采巷道布置、巷道快速掘进技术、综采过断层技术、采面快速搬家技术等方面分析了湖南煤矿复杂煤层条件下实施综合机械化采煤工艺存在的问题,并提出了解决这些问题的对策.研究结果表明,在现已成功实施普通机械化采煤工艺的采煤工作面是完全可以实施综合机械化采煤工艺的,值得从政策、资金等方面予以支持.

我国煤矿井下复杂地质条件下钻探技术与装备进展

针对我国煤矿井下碎软煤层、坚硬岩层、冲击地压地层、破碎带、水敏性地层等复杂地质条件下钻探技术需求和存在的问题,总结了碎软煤层本煤层钻进与筛管护孔、碎软煤层梳状钻孔定向钻进、复杂顶板高位钻孔定向钻进、全断面硬岩穿层钻进、冲击地压卸压钻进等技术与装备方面的研究和应用情况。提出了碎软煤层双管护孔定向钻进及碎软煤层旋转定向钻进技术与装备的研究思路,有助于提升碎软煤层钻进的钻孔深度、护孔筛管直径和钻进效率等,而碎软煤层定向钻进技术与配套装备的完善也将促进碎软煤层瓦斯抽采模式的变革。防冲防突钻孔机器人的研究是煤矿井下复杂地质条件下钻探技术与装备的发展趋势,可为无人化矿井建设奠定基础;除此之外,还应着力解决好局部复杂地层对钻进的影响,更好地促进智能化钻探技术装备的进步,为煤矿安全高效生产提供保障。