The controlling effect of thick-hard igneous rock on pressure relief gas drainage and dynamic disasters in outburst coal seams

Intrusive igneous rock is usually found in the overlying strata above mining stopes, and its occurrence, lithology, and distribution play important roles in coal mining safety. Of the numerous coal mine disasters in China, a large number have been caused by magma intrusion. Magmatic activity is intense and widely distributed in the Haizi Coal Mine which has suffered eleven coal and gas outburst accidents and one water inrush accident under a thick-hard igneous rock with 120-m-thick. Based on theoretical analysis, laboratory testing and field observations, we found that under the effect of thermal evolution and entrapment of the igneous rock, the coal pore structure developed, the gas adsorption capacity was enhanced, and the risk of gas outburst increased. The igneous rock, as the main key stratum, will not subside or break for a long time after mining. The closing time of fractures and separations is also prolonged and provides good conditions for gas drainage. The distant penetration borehole for draining pressure relief gas is proposed which can ensure effective gas drainage and reduce the number of rock laneways. However, with the continuous mining of a large area, the igneous rock could suddenly break, instantly releasing a tremendous amount of elastic strain energy, which will easily induce the occurrence of complex dynamic disasters, such as rock bursts, water inrush, gas outbursts, and surface subsidence. Based on the cause analysis of dynamic disasters, a reasonable goaf filling height is proposed for fully eliminating mine disasters under the special geological condition.     

Study on the Fracture of Hard and Thick Sandstone and the Distribution Characteristics of Microseismic Activity

The movement of hard and thick key stratum during underground coal extraction via longwall top coal caving differs from that of other types of overlying strata. Therefore, numerous problems such as roadway instability, rock burst and strong mining-induced mine seismicity will be encountered as a result of the fracture of a hard and thick key stratum. The key to controlling the behavior of strata is to understand the movement and fracture pattern of the hard and thick key stratum. Taking the 103_up02 working face of Baodian coal mine as a case study in this study, according to the in situ measured microseismic data, the rule of fracture of overlying hard and thick sandstone caused by working face mining is studied, and the mechanism of dynamic pressure impact induced by hard and thick strata fracture is explained. Finally, the dynamic pressure control technology is put forward. The research results are of great significance for coal mining under hard and thick strata, mastering the fracture rules of hard and thick strata and predicting dynamic disasters.     

上覆硬厚岩层破断运动及断顶控制

硬厚覆岩的破断与结构将发生显著的变化。针对汝箕沟煤矿二2煤层上覆厚层石英砂岩条件,采用现场实测、数值模拟、理论分析及现场试验等方法,研究了硬厚覆岩裂隙发育特征、破断运动、矿压显现特征及断顶控制技术,为硬厚覆岩工作面灾害防治提供了依据。研究表明,硬厚石英砂岩的微观结构致密完整,呈现大面积悬空、大步距破断运动,引起强烈的支架动载,甚至导致工作面风流逆转、沟通上部采空区隐形火区;硬厚岩层破断运移后产生明显的离层空间,并在开切眼上部和工作面上部及采空区中部形成覆岩主裂隙带,且发育高度大于经验计算数值,甚至与上方采空区沟通诱发灾害;实施开切眼深孔断顶爆破及降低工作面采高,有效缩短了硬厚岩层的初次破断步距,降低了支架动载及主裂隙带高度。     

断层作用下深部开采诱发冲击地压相似试验研究

以典型断层型冲击地压矿井为例,采用相似材料模拟试验方法,基于覆岩空间结构失稳与断层活化耦合致灾原理,分析了巨型逆冲断层下盘煤层开采采场覆岩运动过程、工作面倾向支承压力及断层面的应力变化规律,研究了巨型逆冲断层影响下巨厚坚硬顶板易冲击煤层冲击地压显现特征。试验结果表明：煤层开采诱发巨型逆冲断层冲击灾变过程分为3阶段：第1阶段,受煤层采动影响,上覆岩层发生空间运动,煤体中形成明显高应力集中区;第2阶段,覆岩多层空间结构演化诱发断层活化,断层活化导致空间结构外部岩体回转,给空间结构施加外部载荷,造成空间结构失稳加剧,煤岩体的应力激增,影响范围扩大;第3阶段,断层滑移释放能量,提供动载荷。根据应力监测数据变化规律,划分了逆冲断层的明显影响区域,研究结果为断层影响下煤层开采的防冲策略与设计提供可靠依据。     

Assessment of rigid overlying strata failure in face mining

The method of overlying strata failure assessment of extracted seams is based upon the simultaneous assessment of surface subsidence and seismic activity, considering the spatiatemporal progress of mining, depending on the character of the rock mass. The rigid overlying strata failure assessment results in finding whether a failure of the firm overlying rocks occurred or whether a strutting arch was formed over the mined-out area. The practical importance of the overlying strata failure assessment consists in determining the size of the mined-out area at which the com-plete failure of the rigid overlying strata occurred and in the assessment of the current stress condition of the overlying strata failure. The assessment method is applicable in deep mine workings where thick coal seams are being mined by means of the method of longwall mining with controlled caving. The results of this method are used to amend contemporary known methods of rock-burst protection, namely (regarding the use of surface measurements for the evaluation) in overlying strata areas.     

彬长矿区“井上下”立体防治冲击地压新模式

随着煤矿开采强度的不断增大,矿井逐渐向深部转移,冲击地压灾害日益严峻。而深部冲击地压矿井往往存在一层或多层坚硬厚岩层,这些坚硬顶板厚度较大,整体性强,突然断裂时会释放大量弹性能,易引发冲击地压事故,严重制约矿井安全生产。以陕西彬长矿区孟村矿为例,针对矿区内煤层埋藏深、普遍存在多种坚硬厚岩层的特殊情况,提出针对性治理措施：对顶板上方0～80 m范围内厚度超过10 m的坚硬厚岩层进行破断、弱化处理,对煤层上方0～30 m范围的低位岩层采取顶板深孔爆破预裂措施,对煤层上方30～60 m范围内的中位坚硬岩层采取顶板定向长钻孔水力压裂措施,对煤层60 m以上高位坚硬岩层采取地面水平井分段压裂措施;使高、中、低位顶板产生的裂缝在垂向上实现贯穿,将顶板“切割”成相对规则的“块状”结构,使上覆岩层应力由“硬传递”转化为“软传递”;并结合煤层大直径孔卸压、煤层爆破等煤层卸压措施,形成了区域与局部相结合、煤层与岩层全覆盖的“井上下”立体防治模式。工程实践证明：采用“井上下”立体防治模式后,工作面103 J以上微震事件降低88%,周期来压强度降低23%,来压持续时间缩短61%,防冲效果良好。该技术模式的成功...     

特厚煤层小煤柱沿空掘巷数值分析及应用

沿空掘巷开采技术成功的关键主要取决于采场覆岩稳定的时间和沿空掘巷的位置。采场采动岩体运动导致围岩应力重新分布,动态采场应力作用于围岩并使其状态发生灾变是发生矿山灾害的根本原因。特厚煤层分层综采巷道布置（包括内错、外错和垂直）,合理确定煤柱尺寸、巷道支护方式和参数选择能够最大可能发挥围岩的自承能力,是提高巷道稳定的重要保证。在稳定的内应力场范围内布置小煤柱护巷,能够明显提高巷道围岩稳定状态,减少巷道维护费用。通过理论分析、数值模拟和现场实测等方法,对特厚煤层下分层沿空掘巷小煤柱不同巷道布置设计,通过煤柱的应力、应变和位移进行对比分析,确定特厚煤层下分层沿空掘巷合理的巷道位置和煤柱尺寸及上覆岩层防控技术,并得到工程验证是正确可靠的,从而为特厚煤层小煤柱开采技术提供了重要的科学依据。     

Mining Thick Coal Seams Under Thin Bedrock–Deformation and Failure of Overlying Strata and Alluvium

In underground coal mines, the failure of overlying strata can have disastrous effects where the working face is overlain by thin bedrock covered with thick alluvium. Roof failure under these conditions can cause a massive water and sand inrush. This paper presents a case study for a design to prevent such disasters in the Baodian mine, China. First, the engineering geological and hydrogeological conditions of the overlying lithified strata and the alluvium were obtained from field and laboratory studies. Numerical models were then built with different bedrock thicknesses using distinct-element modelling software. The deformation, failure, and subsidence of the overlying strata during simulated coal mining were studied using these computer models. Finally, the results of the model studies were combined with the geological data to design a reasonable layout for the longwall panel to be mined in the Baodian mine. Initial results showed that the alluvium was somewhat impervious and water-poor. The models showed that the first caving and weighting intervals of the roof decreased with decreasing bedrock thickness, and decreasing bedrock thickness also increased maximum subsidence of the alluvium. The maximum height of the caving zone and the minimum height of the sand-prevention coal and rock pillars were 34 m and 46 m, respectively. Knowing this allowed a somewhat shorter (204 m) but safe working face to be designed. This research provides a good background for the design of safe mines under similar conditions.     

软硬相间岩层底板变形研究

引入损伤变量ω理论,分析水平状软硬相间岩层在竖向应力下的应力-应变关系：再引用弹性模量E和岩层厚度L两个变形参数建立软硬相间岩层底板变形参数方程,得出竖向应力随着底板深度的增加而减小的规律：运用数值模拟软件,建立煤层开采模型,模拟软硬相间岩层底板在采动作用下的变形过程。通过数值分析底板在采动作用下的应力-应变关系和位移特征,发现竖向应力作用下软岩受到的水平应力比硬岩大,竖向应变也比硬岩大,而竖向应力和水平应变变化不大,认为在采动影响下软硬相间岩层底板中的软岩具有吸收更多的应变能来保护软岩下硬岩的变形特点。     

矿井地质动力环境评价方法与冲击地压矿井类型划分研究

冲击地压等矿井动力灾害的发生受多因素影响,是自然地质动力环境条件和开采工程扰动条件耦合作用的结果。冲击地压发生的时间、空间、强度等特征与矿井所处区域地质动力环境有关,由于不同煤田、不同矿区、不同矿井所处的区域地质动力环境存在差异性,致使有些煤矿不具备发生冲击地压的地质动力环境条件,而有些煤矿发生冲击地压的类型也不同。提出矿井地质动力环境评价方法,并构建评价指标体系。在地质动力环境研究中,主要考虑自然地质条件下外部地质体的动力作用对冲击地压的影响效应,确定构造凹地反差强度、矿井区域断块构造运动、断裂构造、构造应力、开采深度、上覆岩层结构特征、本区及邻区判据条件等影响因素为评价指标,根据各因素对矿井的影响程度情况,给出每个因素的不同量化评价值。综合量化评价结果,判定矿井是否具有发生冲击地压的地质动力环境：(1)当综合评价指标值n为0～0.25,表明矿井不具备冲击地压发生的地质动力环境;(2)当综合评价指标值n为>0.25～0.50,矿井具有弱冲击地压发生的地质动力环境;(3)当综合评价指标值n为>0.50～0.75,矿井具有中等冲击地压发生的地质动力环境;(4)当综合评价指标值...     

基于数值模拟的采动影响下覆岩裂隙演化过程分析

以平顶山东部矿区为工程背景,利用岩石真实破裂过程分析软件（RFPA2D）,模拟了采动影响下覆岩介质损伤的动态发展过程。数值模拟结果表明,采动裂隙的形成过程是一个复杂的演化过程,在加载初期覆岩介质损伤小,声发射现象不明显,应力和位移基本上无变化,无明显裂隙产生。随着加载步的增加,覆岩内部介质出现破裂,声发射次数、应力值和位移值不断增加,此时裂隙场处于孕育、不断积累并扩大阶段。当声发射次数、应力值、位移值都达到最大值时,裂隙经过萌生、扩展之后形成宏观裂隙,进而导致煤岩体由弹性状态转变为塑性状态,使覆岩大面积垮落。该数值模拟结果对平顶山东部矿区的开采具有巨大指导意义。     

煤矿地下水库岩体碎胀特性试验研究

鉴于岩石碎胀特性对于煤矿地下水库储水能力及地表沉陷的重要影响,选取神东矿区某矿22615面为工程背景,利用相似材料模型试验探究采空区垮落岩体应力及碎胀系数分布规律,明确垮落岩体应力-碎胀系数关系,并通过岩石压实试验进行验证,揭示饱水岩石压实特性。研究结果表明：沿采空区走向,边界附近老顶悬臂梁结构限制覆岩下沉,垮落岩体应力最低仅为0.32 MPa,碎胀系数最大达1.48;中间区域老顶结构失稳覆岩完全下沉,垮落岩体应力趋于1.5 MPa,碎胀系数降至1.09。沿采空区垂向,垮落岩体应力随高度负相关改变,而碎胀系数成正相关变化。无论沿采空区走向或垂向,垮落岩体碎胀系数与应力均满足负对数关系。与自然岩石相比,受载饱水岩石碎胀系数减幅更为明显,两者相差8.514%,为煤矿地下水库储水量和地表沉降量预测提供了基础理论依据。     

采动覆岩裂隙分布及其空隙率特征

利用弹性薄板理论和关键层理论,对采空区上覆岩层的下沉进行定量描述,研究采动影响下覆岩裂隙的分布特征,得到了基于相对下沉量的覆岩规则移动带空隙率的近似公式。研究表明,覆岩裂隙场内,裂隙数量分布以两边为多,中部较少,在关键层下部的岩层往往产生较大的离层空间;随着岩层深度减小,空隙率逐渐变小,覆岩底部,空隙率曲线沿走向呈现马鞍状,在关键层或者硬岩起作用的区域形态发生改变,曲线形态逐渐变成拱状。其结论可应用于岩体渗流研究及瓦斯综合治理。     

Research on the Evolution Law of Spatial Structure of Overlying Strata and Evaluation of Rock Burst Risks in Deep Well Strip Mining

Strip mining in mines is one of the main mining methods to control surface subsidence and protect the ecological environment. In recent years, strip mining has induced frequent rock burst accidents due to the increase in mining intensity and mining depth. Based on two typical deep strip mining accidents, the characteristics of the changes in spatial structure of the overlying strata caused by strip mining are studied, and the influencing factors of the occurrence of strip mining rock burst are analyzed. A support pressure calculation model is proposed, and estimated and verified in a mine after an analysis of the change law of the overlying strata structure in strip mining and research on the distribution and evolution law of support pressure. Based the above research, a risk evaluation model of the strip mining face is proposed based on the possibility index method, the 4203 working face of a mine is evaluated. Compared with the numerical simulation results, this method is well consistent with the theoretical calculation model. It can be seen that this method has strong practicability and is of great significance for studying the rock burst characteristics of coal seams in strip mining and evaluating the risk of rock burst of coal seams.

     

辽宁省抚顺矿区宏观地质结构及其工程效应分析

抚顺采煤已有百余年历史,由于各种原因造成了一系列地质灾害:滑坡、矿震、地表沉陷和地裂缝等。矿区的中部和西部的形成带状的地表拉裂和建筑物破坏;软岩区形成大面积的地表沉陷,硬岩区形成脆性和线性拉裂,这些现象与矿区地质结构是分不开的。通过对矿区地质结构和矿区地层构造演化研究,认为抚顺矿区地质灾害是发生在花岗岩与火山岩之间的"凹槽"内,是有限的。根据矿区主断层F1、F1A交汇点位置,将矿区地质结构类型划分为三种类型,并通过FLAC二维数值计算对三种类型的典型剖面进行了数值模拟和验证,合理地解释了矿区地质灾害的产生机理和发展趋势,为抚顺矿区地质灾害综合治理和采煤规划提供了科学依据。采用地质结构控制论来研究城市地质灾害提供了新的思路和方法。     

开采上保护层对巨厚砾岩诱发冲击矿压的减冲机制分析

为研究开采上保护层对巨厚砾岩断裂诱发冲击的防治作用,根据跃进煤矿25采区的地质条件和采掘条件,将25110工作面下巷作为研究对象,从理论上分析了动静载叠加诱发冲击矿压的机制以及开采上保护层后的防冲原理,数值模拟研究了未开采上保护时和开采上保护层后在同等强度的动载扰动应力的影响下巷道底板的位移、速度、应力以及塑性区的变化规律,进行相似模拟试验研究了人工震源的作用下未开采上保护时和开采上保护层后巷道底板的加速度和动应力响应规律。结果表明,上保护层开采后能够有效地释放围岩内部的高应力,且采空区顶板自然垮落,形成的软弱松散岩层结构,能够更好地起到对动载扰动应力波的衰减作用,从而降低了冲击矿压发生的可能,一定程度上能够较好地防治冲击矿压。研究成果对巨厚砾岩下冲击矿压的防治具有一定指导意义。     

巨厚坚硬岩层下煤层开采\

以淮北矿业集团巨厚坚硬火成岩岩床下煤层开采发生特大突水事故为例,勘查测试了突水的水文地质工程地质条件,对比国内外其他矿山突水水害特征,认为该突水为一种新的煤矿突水类型——\     

Investigation into the Behaviour of a Support System and Roof Strata During Sublevel Caving of a Thick Coal Seam

Monitoring of strata control parameters and behaviour of a powered support was carried out during an experimental trial of a mechanized longwall sublevel caving face for exploitation of a 7.5m thick coal seam. Field observations indicated that the requirement of support density for underwinning of top coal by sublevel caving under intact strata is different from that for underwinning under broken and fractured rock mass. Analysis of the leg closure observations and support resistance variations during different mining cycles showed rapid increase of the setting load density of the support in relation to the yield load density. This resulted in a large amount of leg closure during mining cycles of the sub level caving face under broken rock strata. Due to operational constraints, the field observations could not provide enough information to visualize the behaviour of the overlying rock strata. Simulation of the field conditions was therefore performed on a physical model to bridge this gap of information. Results of laboratory investigations on the physical model are combined with those of the field to explain the critical behaviour of the support system during sublevel caving under broken rock strata.     

强反射能量屏蔽补偿在渤海C构造中的应用

在渤海海域西南部广泛分布着新生界的溢流相火成岩,高速层的能量屏蔽是造成火成岩发育区下覆地层地震波场信号弱的主要原因之一。传统的自动增益控制方法(AGC)在分时窗滑动补偿下覆地层被屏蔽的弱信号的同时,破坏了火成岩与下覆地层的能量关系,且时窗内火成岩层之间的弱信号也无法得到有效恢复。这里从反射系数与振幅补偿的关系出发,基于模型论证了利用射线追踪提取地震波传播路径上的反射系数来求取补偿因子,进而开展相对振幅补偿过程的有效性。在渤海油田多个构造的振幅补偿结果,较好地恢复了火成岩屏蔽地层的能量损失,且地层间的振幅关系也得到相对保持,取得了较好的实际应用效果。     

地下水位下降对采矿覆岩下沉影响探析

地下采煤会导致地表下沉盆地的形成。然而地下水尤其是承压水的流失即水位降低对地表下沉盆地的形成存在不可忽视的影响，而对两者之间的关系及其过程的力学机理是岩移领域亟待研究的课题之一。矿区地下水位降低的主要原因为承压水通过采动裂隙向下渗流、煤层开采前顶板岩溶含水岩层的疏干以及地面人为钻井取水。根据对一具体矿区地下水位下降对地表沉陷影响实测数据的分析得出，在以采煤为主导条件导致地表下沉的过程中，几乎全部的开采沉陷量中均包含有由于含水层释水而造成的沉陷量。通过对上覆岩层力学机理分析，指出水位降低对覆岩移动、地表下沉的影响是由于一定地质条件下可渗水性岩石的物理力学特性、渗水对其它岩石的软化、释水后原冲积层的压密固结以及水渗透过程中的水岩耦合作用等因素综合作用所致。同时，在以上理论的基础上还探讨性地建立了地下水位下降对地表下沉贡献模型，在此模型基础上可以建立2个或2个以上影响因素对地表下沉的贡献模型。最后以框图形式概括了地下水位下降及其对地表下沉影响的综合过程。