Analysis of the Harmfulness of Water-Inrush from Coal Seam Floor Based on Seepage Instability Theory

A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the distribu-tion of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D). The permeability parameters of the coal seam floor are described given the relationship between permeability parameters. Strain and the water-inrush-indices were calculated. The wa-ter-inrush-index was 67.2% when the working face was pushed to 100 m,showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m,showing that water-inrush is quite probable. The results show that as long-wall mining is pushed along,the failure zone is enlarged,the strain increased,and fissures developed cor-respondingly,resulting in the formation of water-inrush channels. Accompanied by the failure of the strata,the perme-ability increased exponentially. In contrast,the non-Darcy flow β factor and the acceleration coefficient decreased ex-ponentially,while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly.

Prediction and control of rock burst of coal seam contacting gas in deep mining

By analyzing the characteristics and the production mechanism of rock burstthat goes with abnormal gas emission in deep coal seams,the essential method of eliminatingabnormal gas emission by eliminating the occurrence of rock burst or depressingthe magnitude of rock burst was considered.The No.237 working face was selected asthe typical working face contacting gas in deep mining;aimed at this working face,a systemof rock burst prediction and control for coal seam contacting gas in deep mining wasestablished.This system includes three parts:① regional prediction of rock burst hazardbefore mining,② local prediction of rock burst hazard during mining,and ③ rock burstcontrol.

Application of A New Anchor Cable Mounting Rod in the Lower Soft Coal Seam of Splitting and Merging Coal

To obtain the deep displacement of the coal seam in the working face,multi-point displacements were installed in the coal seam, but the installation of multi-point displacement is differen tunder different geological conditions. This paper is based on the splitting and merging of 7_1 coal and 7_2 coal in Huaibei Mining(Group) Co., Ltd., and analyzes properties of the roof andcoal in the 7_2 coal of the lower coal seam of bifurcation area, and calculates the damage depth of the floor in the process of 7_1 coal mining. The multi-point displacement meter installation is often challenged by hole collapse, stuck pole and broken installation rod in 7_2 coal of the soft coal seam of bifurcation area, as a result, the base points can't be installed in the specified location. In view of this, this paper adopts a new anchor cable mounting rod which can install the whole base points to the specified location without stuck pole or broken mounting stem. All the basic displacement data can be obtained, and the law of mine pressure appearance in stope and tunnel can be accurately controlled, which can be used to maintain the stability of roadway and the safety of stope.

Comprehensive evaluation of water-inrush risk from coal floors

Lower groups of coal seams are presently being mined in the Yanzhou coal mining area. We need to evaluate the risk from water-inrush from coal floors in order to have safe production in the lower groups of coal seams in mines. Based on a system-atic collection of hydrogeological data and some data from mined working faces in these lower groups, we evaluated the factors affecting water-inrush from coal floors of the area by a method of dimensionless analysis. We obtained the order of the factors af-fecting water-inrush from coal floors and recalculated data on depths of destroyed floors by multiple linear regression analysis and obtained new empirical formulas. We also analyzed the water-inrush coefficient of mined working faces of the lower groups of coal seams and improved the evaluation standard of the water-inrush coefficient method. Finally, we made a comprehensive evaluation of water-inrush risks from coal floors by using the water-inrush coefficient method and a fuzzy clustering method. The evaluation results provide a solid foundation for preventing and controlling the damage caused by water of an Ordovician limestone aquifer in the lower group of coal seams in the mines of Yanzhou. It provides also important guidelines for lower groups of coal seams in other coal mines.

Lateral Stress Concentration in Localized Interlayer Rock Stratum and the Impact on Deep Multi-Seam Coal Mining

To explore the impact of lateral stress concentration in interlayer rock stratum on the exploitation of protected coal seam, a field experiment was carried out in a multi-seam mining structure. Lateral stress redistribution and interlayer rock failure behavior were surveyed. Then an assistant numerical investigation was implemented to evolve the effect of liberated seam mining and its influence on stress reconstruction in surrounding rock mass. The cause of lateral stress concentration and its impact were discussed finally. Key findings turn out that a certain lateral stress increases in interlayer rock stratum and concentrates on its lower region. Lateral stress concentration and interlayer rock failure are interactional. The former is an inducing factor of the latter;the latter promotes the increase of concentration degree. Extent of lateral stress concentration increases to the maximum as seam distance is about 50 m. But the efficacy of liberated seam mining decreases as the seam spacing gets larger. Protected seam mining is then classified based upon the impact of lateral stress concentration, which helps to prevent the rock burst hazard and then to achieve a reliable mining in deep mines.

Roadway failure and support in a coal seam underlying a previously mined coal seam

The influence of an upper,mined coal seam on the stability of rock surrounding a roadway in a lower coal seam is examined.The technical problems of roadway control are discussed based on the geological conditions existing in the Liyazhuang Mine No.2 coal seam.The stress distribution and floor failure in the lower works after mining the upper coal is studied through numerical simulations.The failure mechanism of the roof and walls of a roadway located in the lower coal seam is described.The predicted deformation and failure of the roadway for different distances between the two coal seams are used to design two ways of supporting the lower structure.One is a combined support consisting of anchors with a joist steel tent and a combined anchor truss.A field test of the design was performed to good effect.The results have significance for the design of supports for roadways located in similar conditions.

深部近距离煤层群下分层巷道分区支护技术

为实现深部近距离煤层群下分层巷道安全,以张双楼煤矿21916工作面为工程背景,分析了工作面冲击地压影响因素,划分了21916工作面掘进期间巷道冲击危险区域;建立了煤层合并区域下分层回采巷道数值模型,研究了9煤层21916工作面巷道内错7煤采空区不同距离时应力和位移分布规律,确定了下分层巷道合理位置;基于冲击危险区域划分结果,提出了分区支护技术,并设计了支护参数。现场实测表明,下分层巷道最大两帮移近量为164 mm,最大顶底板移近量为84 mm,顶板深部和浅部的离层量不大于3 mm,帮部锚杆和顶部的锚索受力变化较小,顶锚杆受力从8 kN增加到12 kN后趋于稳定,表明21916工作面巷道布置合理,分区防冲支护技术合理,支护质量与效果显著。研究结果可为类似条件工作面防冲支护提供借鉴。

深部软岩巷道支护对策研究

深部软岩围岩稳定性控制问题日益突出。以东周窑煤业为研究区,通过现场勘察获得了巷道变形破坏特征;通过数值模拟分析了巷道变形、围岩倾斜与软弱层位置之间的关系,得出了软岩巷道的变形破坏特征影响因素;基于数值模拟结果,提出了深部软岩巷道支护新型设计方案。结果表明,新型支护方案控制效果良好,对类似工程具有指导意义。

复杂条件下大倾角综采面顶板管理技术研究与应用

文章以某矿2505W工作面为对象,结合大倾角煤层矿压显现规律及底板破坏深度理论,开展采场顶板“三带”现场观测,并与现场实际观测结果进行对比验证。结果表明:(1)在水泥与水玻璃作用下,煤层伪顶与直接顶裂隙得到有效填充与固结,强度未得到有效提高,但完整性得到加强,杜绝了破碎顶板对正常推采的影响;(2)采用液压岩石劈裂技术,可实现过断层期间岩石打眼与破碎平行作业,对工作面顶板无扰动,比爆破作业每循环节省43%时间;(3)实现平均日循环6刀,比传统爆破法过断层及铺网、打锚带、剥帮等顶板管理方式推采效率提升1倍以上。针对工作面受上覆及下伏煤层采动影响、断层切割顶板导致顶板破碎等问题,文章提出了用水泥与水玻璃超前预注浆加固顶板、液压岩石劈裂机替代钻爆法等顶板管理关键技术。

特厚煤层大断面软岩巷道底鼓治理措施与效果

以斜沟矿特厚煤层大断面软岩巷道反复强底鼓工程实际为背景,综合运用理论计算与现场监测方法,结合巷道底板岩层特性,判断巷道底鼓类型,引用巷道极限平衡理论,计算得出巷道极限平衡区最大深度为11.05 m,设计“双应力壳-梁”控制巷道底鼓措施。现场应用的监测结果表明,采用新的控制措施后,巷道底鼓量最大为17.49 cm,巷道底板围岩控制措施取得较好效果。

深部煤层不同类型隐伏构造致灾规律研究

深部开采过程中,矿井地质类型复杂,在“三高一扰动”条件下,隐伏构造附近极易引发煤与瓦斯突出等煤岩动力灾害。为明确隐伏构造诱发动力灾害的机制,以平煤股份八矿为工程背景,数值模拟研究了不同采掘方向正、逆断层及两者同时存在时的应力-应变演化特征及致灾规律,分析了不同隐伏构造对掘进头的影响。结果表明:掘进遇单一断层,应力-应变集中在工作面前方及断层内部,掘进遇正断层更易产生应力集中,且应力集中区域范围更大,在同等掘进距离下,逆断层主应变略大于正断层;随着掘进距离的增加,当掘进距离增加至15 m时,应力-应变集中区逐渐重合,最终在断层区域形成应力-应变叠加区;掘进遇多断层,应力集中在工作面前方、两断层之间的构造煤上。遇正-逆断层、逆-正断层,叠加应力-应变分布特征表现出差异性,遇正-逆断层,叠加应力-应变主要分布在正断层附近,而遇逆-正断层,两断层之间构造煤中应力-应变也显著增加。逆断层及逆断层主导的多隐伏构造附近,应变能增长速率更大,更有利于应变能积聚,煤与瓦斯突出危险性增加。在采动应力、断层构造应力及煤岩体中的静应力三者的共同作用下,最终引发煤与瓦斯突出等煤岩动力灾害。多隐伏构造较单一构造更易产生应力集中,煤岩动力灾害危险性增加。

浅埋煤层群上下层位土层与基岩层协同隔水稳定性研究

浅埋煤层顶板突水是由于导水裂隙带贯穿隔水层而引起的,随着煤层群的下行开采,土层与基岩层的协同隔水机理亟待明确。为了分析隔水土层在煤层群下行开采工程背景下的破坏机理,以便准确预测煤矿顶板突水问题,以陕北神府矿区韩家湾煤矿2−2、3−1和4−2煤下行开采为研究背景,通过原位钻孔取心试验得出不同埋深的隔水土层性质的差异;通过建立上层位隔水土层渗透扩展力学模型来描述裂隙发育形态;采用土−岩复合隔水层力学模型,在“给定变形”条件下计算下层位隔水土层处于整体稳定状态时的力学判据。研究表明,隔水土层根据其性质不同可以分为上层位隔水土层和下层位隔水土层;通过比较总载荷与上层位隔水土层抗拉强度的大小,当总载荷小于等于上层位隔水土层抗拉强度时裂隙不再向下发育从而得出裂隙发育长度;在“给定变形”条件下,当下层位隔水土层长边中部位置处产生的拉应力小于或等于拉伸强度阈值时,下层位隔水土层整体结构处于稳定状态,不会产生拉伸破坏;根据韩家湾煤矿地质情况进行数值模拟,模拟结果与理论分析结果相吻合。研究可为相似地质条件下顶板突水预测提供参考。

不同底板岩性条件下煤柱宽度对巷道底鼓影响

为探究深部开采中不同底板岩性条件下煤柱留设宽度对巷道底鼓影响机理,以赵庄煤业3104巷为工程背景,采用理论分析、数值模拟、现场试验的方法,研究了深部厚煤层中回采巷道煤柱宽度参数变化,对不同岩性底板的承载应力场分布、最大破坏深度、破坏形态的影响。结果表明:巷道底鼓量及煤柱宽度与底板强度系数呈力学负相关;留设12 m煤柱时,3种岩性底板均无法支承上覆岩层载荷;留设16 m和20 m煤柱时,泥岩底板条件下破坏层位向巷道右侧煤岩体更深处转移,细砂岩、砂质泥岩底板载荷功能良好,破坏层位分布在巷道左侧及支护体围岩表层;提出了3104巷支护改进方案,有效降低了巷道底鼓。

倾斜特厚煤层上分层开采时下分层煤体载荷及渗透率演化规律研究

为了得到倾斜特厚煤层上分层开采时下分层煤体载荷及渗透率演化规律,以新疆硫磺沟煤矿9-15(06)工作面为研究对象,构建了采空区底板应力传递模型,模拟了随着上分层推进时下分层煤体载荷演化过程,并以此为下分层采集煤样应力路径,开展了下分层含瓦斯煤应力加卸载实验,得到了下分层煤体渗透率演化规律。结果表明:随着上分层推进,下分层煤体垂直应力经历了原岩应力、应力增加至支承应力峰值、支承应力峰值后卸压、应力升高恢复稳定;沿煤层倾向,下分层煤体进入采空区后,由倾斜上部至下部,煤体应力最大恢复程度逐渐增加;下分层煤体渗透率经历了初始渗透率、渗透率下降、渗透率上升、渗透率突增、渗透率降低恢复稳定;不同位置煤体进入采空区后,渗透率最大恢复程度随应力最大恢复程度的升高而增加。研究结果为揭示下分层煤体瓦斯涌出时空演化规律奠定了基础。

煤层群上下保护层开采围岩应力时空演化规律及应用研究

为实现煤层群上下保护层开采被保护层卸压瓦斯高效抽采,采用数值模拟方法研究上下保护层开采后围岩应力分布及演化规律,根据卸压范围分布实现卸压瓦斯抽采钻孔精准布置。研究结果表明:上下保护层双重开采,有效降低被保护层的应力,卸压范围增大。下保护层开采后被保护层倾斜上下边界卸压角分别为87°、72°,走向卸压角为63°;上保护层开采后被保护层倾斜上下边界卸压角分别为76°、79°。卸压抽采钻孔瓦斯浓度从卸压前的30%~40%增加到卸压后90%以上,单孔瓦斯流量从卸压前0.03~0.08 m^(3)/min增加到卸压后的1.1~1.85 m^(3)/min,瓦斯纯流量呈现数10倍增加,但工作面推过150 m左右,抽采数据快速降低,卸压瓦斯抽采存在显著的空间和时间效应。研究结果可促进多重保护层开采卸压瓦斯抽采技术发展。

近距离煤层开采底板应力演化规律及围岩稳定性研究

为了研究近距离煤层开采诱发围岩失稳问题,以贵州林东煤业龙凤煤矿5#、9#煤层回采巷道为工程背景,采用数值模拟的方法分析了上位煤层开采过程中底板应力演化规律及周围回采巷道变形破坏特征。研究结果表明:距底板不同法向距离的垂直应力在横向上呈对称分布且变化规律基本一致,纵向上的分布随着深度的增加呈线性增长趋势;当工作面分别推进不同距离时,巷道呈现不同的变形破坏特征;相邻区段回风巷与下位9#煤层回风巷围岩应力增加,且围岩应力呈非对称性分布,9#煤层运输巷处于卸荷区,但围岩力学性质劣化程度高,围岩承载力降低;处于应力增高区的巷道围岩以剪切破坏为主,处于卸荷区的巷道围岩以拉伸破坏为主。

受断层控制的下组煤开采底板变形特征及突水危险性探究

为了探究杨村煤矿十采区下组煤17煤层首采10703工作面断层突水危险性,在系统分析其地质及水文地质条件基础上,确定了该工作面属于典型的受断层控制的带压开采范畴,主要突水含水层为十三-十四灰和奥灰。在此基础上,建立了集完整和有断层于一体的10703工作面所在区域的三维工程地质模型,采用数值模拟方法对比模拟获得了16上和17煤两薄煤层依次开采后受断层控制的底板变形破坏深度和特征。在此基础上,采用安全带压系数法系统评价了完整和有断层条件下十三-十四灰和奥灰对10703工作面带压开采突水危险性,结果认为均是安全的,与突水系数法结果进行了比较。研究结果对该工作面带压开采底板水防治具有很好的参考价值。

开采扰动下深井松软岩层巷道围岩变形特征及防控技术研究

针对深井松软煤巷围岩变形破碎、巷道支护困难等问题,以城郊煤矿21106工作面沿空巷道为工程背景,通过理论分析、数值模拟及现场试验,综合探究了巷道围岩变形破坏机制及防控策略。研究发现顶板横向受力、巷道等效跨度、厚硬顶板是巷道围岩损伤破坏影响因素。横向受力增大、等效跨度增长以及围岩强度降低都会加剧围岩破坏程度。基于巷道变形破坏主控因素,提出煤柱侧向切顶+注浆加固并对破碎区域补充锚索强化支护的防控策略,对后续工作面巷道支护提出全长锚固+顶板外侧补充2排锚索+煤柱侧补充2排锚索、顶板外侧补充2排锚索+煤柱侧向切顶2种防控方案。不同方案下巷道围岩变形及应力监测结果表明,方案二防治效果更佳,为深井松软围岩巷道变形控制提供了合理依据。

穿越采空区L型瓦斯抽采水平井钻进关键技术

为了深部煤层开采之前能够高效超前抽采瓦斯,保障深部煤层安全开采,L型水平井钻进技术成为地面瓦斯抽采的主要方法之一。针对穿越采空区L型瓦斯抽采水平井钻进施工存在的诸多困难,主要从井身结构设计、穿越采空区氮气钻进技术、水平段钻进轨迹控制技术3个方面,进行了穿越采空区L型瓦斯抽采水平井钻进关键技术研究。将关键技术研究成果成功应用于了M矿区1口穿越采空区L型地面瓦斯抽采井,高效顺利完钻了该井施工,使得目标深部煤层水平段钻进的钻遇率约为90%。