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.

RESEARCH ON DEEP COAL SEAM MINING FLOOR STARTA WATER BURSTING INFLUENCED FACTORS BASED ON ANALYTIC HIERACHY PROCESS

Deep coal seam mining floor strata water bursting is a complicate nonlinear system, whose factors are coupling and influencing themselves. It built the analytic structure model for deep coal seam mining floor strata water bursting, the judgment matrix was found by the expert scoring method, the contribution weights of the influenced factors were given out by the equation analytic process. The thirteen controlling factors and five main controlling factors were put award by analyzing weights, so the result was basically conform to the field practice. The expert scoring method and analytic process can convert the objective fact to the subjective cognition, so it is a method that can turn the qualitative into the quantitative. This can be relative objectively and precisely to study the question of many factors and grey box.

Comprehensive evaluation of water-inrush risk from coal floors

Lower groups of coal seams are presently being mined from water-inrush from coal floors in order to have safe production in the Yanzhou coal mining area. We need to evaluate the risk in the lower groups of coal seams in mines. Based on a systematic 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 affecting 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。

近距离煤层采空区下综放工作面巷道合理位置研究

近距离煤层综放工作面开采空间大,采动强度高,下位煤层回采巷道受上煤层采动影响存在应力集中、巷道支护困难等问题,因此近距离煤层综放工作面巷道合理位置的选取对后期支护控制起到关键性作用。以西露天煤矿2煤层和1煤层1分层为研究对象,综合考虑了上煤层开采时的底板应力降低区域和下煤层开采时的极限平衡区域,确定了下煤层巷道的合理位置应在距离实体煤柱内错22.79 m以上的区域。基于上述理论计算结果,分析了上煤层开采后底板应力分布规律及不同内错距下巷道围岩变形破坏特征及规律,结果表明:①距离采空区底板越近,应力最大值与最小值相差越明显;②随着内错距不断增大,围岩应力和应力集中系数呈现急剧降低-缓慢增大-稳定的趋势,在内错距20~25 m内应力及应力集中系数相对较小;③巷道围岩塑性区范围呈现先减小后增大的趋势,当巷道处于内错20,25 m时巷道围岩破坏相对较小;④巷道变形量随着内错距增大而逐渐减小,当内错距增加至25 m时,巷道围岩移进量基本保持不变;⑤确定巷道合理内错距为20~25 m。工程应用结果表明:巷道采用内错距24 m布置时,巷道围岩松动破坏深度及变形量均在可控范围内,进一步证明了该内错距的合理性。

近距离煤层采掘关系对下位巷道围岩变形规律影响研究

近距离煤层上煤层工作面与下位煤层巷道采掘关系发生变化时,巷道围岩变形失稳机理会更加复杂,而目前针对上煤层工作面与下位煤层巷道推进方向不同时巷道受载动态演化规律及失稳特征的研究较少。以陕北能东煤矿近距离煤层为研究对象,采用理论分析、数值模拟与现场实测相结合的方法,对上煤层工作面回采后下位煤层巷道的稳定性进行了研究。理论分析得出,上煤层工作面开采后所产生的底板裂隙深度为22.5 m,未发育至下位煤层巷道。按采掘空间位置关系将回采工作面与巷道分为相向、相交、背向3个状态,数值模拟当巷道与工作面的空间位置关系发生变化时下位煤层巷道围岩的变形情况,结果表明:①上煤层工作面与下位煤层巷道的采掘关系为相交与背向推进时,巷道围岩应力呈先增后减再增的趋势,在推进距离为90 m时,最大应力为6.5 MPa,应力集中系数为1.49,在推进距离为100~110 m时,巷道围岩应力降低幅度最大,降低了53.2%,在推进距离为150 m时应力最小,为0.95 MPa,之后不断增大,直到恢复至原岩应力。②巷道围岩位移量在推进距离为100~150 m时增长幅度较大,在150 m时顶板位移量达到最大,为0.036 m,随着巷道越接近边界煤柱,其巷道位移量越小。现场实测结果表明:上煤层工作面过下位煤层巷道时,巷道位移量显著增长,顶板最大位移量为3.41 cm,与数值模拟结果一致;相交推进过程中若地质条件简单可以适当加快推进速度,减小上煤层工作面开采对下位煤层巷道的影响。

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。

特厚煤层回采巷道底鼓力学特性及控制研究

针对特厚煤层回采巷道底鼓难以治理的难题,以陕西陕煤曹家滩矿业有限公司(以下简称“曹家滩煤矿”)122110回采巷道作为研究背景,通过现场观测得到特厚煤层回采巷道围岩变形特征,采用理论分析的方法研究区段煤柱上覆关键层破断结构及巷道底鼓机理,通过数值模拟的方法得到底鼓控制措施。研究表明,巷道两侧非对称集中应力导致底板产生非对称底鼓,特厚煤层回采覆岩破断形成不同的承载结构。基于关键层破断特征构建了特厚煤层“下位台阶上位铰接”结构力学计算模型,得到区段煤柱上方载荷计算式;根据滑移线理论建立了巷道非对称底鼓的力学模型,得到了底板破坏深度及位置计算式。由理论计算和数值模拟,得出切槽卸压的底鼓治理措施并计算了切槽参数。通过在曹家滩煤矿现场试验表明,采用3 m×0.5 m(深×宽)切槽方案后,底板平均底鼓量为128.4 mm,较未切槽前减小了81.8%,能够满足综放工作面正常回采需求,可为类似地质工况条件提供参考。

近距离煤层下分层巷道变形破坏机理及控制技术

以铺龙湾煤业81021巷为工程背景,探究近距离煤层下分层巷道变形破坏机理及围岩控制机理,分析近距离煤层下分层巷道修护补强方案,并结合现场工业性试验优化相关支护技术参数。研究结果表明:81021巷两帮表现为剪涨滑移扩容破坏和帮-顶底板界面剪切滑移破坏,两帮煤岩体破碎,帮与顶、底板岩层交界面处发生显著的整体性剪切滑移;两帮变形进一步导致巷道顶板下沉和强烈底臌,顶板及肩窝等处围岩破碎;81021巷采用锚注一体化支护技术后,巷道围岩总体位移量不大,围岩较为稳定,围岩的承载性能得到显著强化和提升,支护安全性和可靠性大大提高。

上薄下厚煤层群上行开采可行性研究

上行开采可有效缓解矿井接续紧张,延长矿井服务年限。以某矿典型的上薄下厚煤层群开采为例,综合采用理论分析、数值模拟等方法对B_(5)煤层上行开采可行性展开研究。结果显示,B_(4)^(2)煤层、B_(5)煤层层间岩层为含单一煤层结构,B_(5)煤层处于在B_(4)^(2)煤层开采后形成的裂隙带范围内,B_(4)^(2)煤层开采后,上覆岩层形成铰接岩梁结构,随着工作面推采,铰接岩梁结构不断向前传递,B_(5)煤层可以保持较好的完整性和连续性。采用4种判别方法对该矿水平采区范围内B_(5)煤层是否具备上行开采的可行性进行验算,明确了B_(5)煤层部分区段具备上行开采的可行性,为高效开采提供了理论依据。

特厚煤层坚硬顶板井下定向深孔水力压裂卸压防冲技术

为进一步解决坚硬难垮顶板导致的冲击风险升高问题,以文家坡矿为例,提出了一种井下定向深孔水力压裂卸压防冲技术,并在4106工作面开展了试验研究,结果表明:提前对厚硬顶板进行卸压处理,岩层强度和完整性大大降低,有利于根本上消除冲击地压对安全生产的严重威胁。压裂期间泵压-时间曲线呈现锯齿状,定向深孔水力压裂能够使得裂缝起裂与扩展,实现顶板有效致裂。在水力压裂作用下,工作面微震活动平稳变化,高级别能量微震事件频次占比显著降低,未超过冲击危险预警临界指标,工作面顶板活动性及微震能量释放保持在较稳定状态,围岩积聚能量能够有序释放,冲击风险显著降低。

深部煤层巷道底鼓注浆加固实践

为解决原相煤矿深部煤层巷道底鼓的问题,以10208工作面轨道顺槽为工程背景,结合现场地质条件对巷道底鼓类型进行分析,依据朗肯土压力理论,对巷道底板受力进行了力学分析,并研究了底鼓的发生机理。采用了巷道顶板、两帮、底板整体考虑的支护理念,确定利用注浆技术对底板进行加固,并对注浆参数进行合理设计。实践表明,10208轨道顺槽进行底板注浆加固后,有效控制了底鼓现象,且保证了顶板和两帮的稳定性,巷道变形量能够满足工作面的安全生产。

厚煤层泥岩底板巷道底鼓控制技术应用分析

山西汾西正旺煤业31103综放工作面运输巷受矿压、底板软岩等多因素影响底鼓问题突出,给巷道使用及采面正常回采带来困难。若采用巷道底板卸压槽、底板注浆以及底板锚索等方式治理底鼓,则面临耗时长、影响巷道正常使用等问题。经分析研判,决定采用降低运输巷围岩应力为主的底鼓控制技术,即通过切顶卸压改善运输巷围岩受力与降低底板受力的方法。结合现场实际,拟定了切顶卸压技术实施方案,实际应用后,巷道底鼓量控制在102 mm以内,底鼓问题得到有效控制。

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。

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。