承压煤岩低气压渗流灾变

为探索含低压瓦斯煤层的瓦斯异常涌出灾变成因与机理,对目前该领域的文献进行了分析与总结,并通过工程案例实证分析,证明了此种灾变的存在;在流固耦合实验系统上,按背景工程约束与加载条件开展含低气压煤样承压物理试验,得到了灾变全程应力-声发射-流量实验数据及试样外表破坏情况;用UDEC,按背景工程边界与加载条件开展气-固耦合离散元数值试验,得到了灾变全程应力-应变--流速-位移速率等实验数据及试样内部破裂情况.研究结果表明:3种研究方法获得了一致性较高的结果,0.4 MPa气体压力下,煤层承压过程应力-煤-气耦合作用,可以导致发生喷出气体的灾变,在煤矿现场多表现为瓦斯异常涌出超限;在单自由度边界条件下施加单向压载,承压煤岩弹性变形前期,气体沿原生裂隙和孔隙呈常速稳态渗流;弹性变形后期,原生裂隙和孔隙被压密,气体呈减速稳态渗流;屈服阶段,扩容新生裂隙产生,气体呈加速非稳态渗流;达到极限荷载或峰后不久,发生气体喷出灾变;采、掘作业面正常通风条件下,气流瓦斯浓度持续降低,是煤层发生瓦斯异常涌出的警示信息,应引起高度重视.     

两软一硬煤层突出控制因素与发生规律

针对两软一硬煤层特殊的瓦斯地质条件,以云盖山井田一矿二1煤层为例,探寻了两软一硬煤层煤与瓦斯突出的控制因素,分析了掘进工作面掘进期间突出预测指标的分布特征,总结归纳了"两软一硬"煤层煤与瓦斯突出发生规律.研究结果表明,由于地质构造变动,云盖山一矿二1煤层产状变化较大,煤层倾角发生急剧变化的地带,地应力集中;受层间滑动构造的影响,煤层厚度变化较大,具有突然增厚、变薄以至尖灭、挤灭现象;二1煤层构造软煤呈连续层状发育.因此,在煤层薄、厚交接处(煤层急剧变化带),小断层附近,应力集中,瓦斯积聚,煤体破坏严重,易发生突出.此项研究,可为地质条件类似矿井开展瓦斯地质研究和瓦斯灾害防治工作提供方法借鉴和理论指导.     

新安煤田煤与瓦斯突出特征及控制因素分析

为了掌握煤与瓦斯突出的特征和控制因素,提高煤矿防突工作的针对性,本文通过统计分析了新安煤田内义煤集团的4个煤与瓦斯突出矿井近年来发生的瓦斯动力现象,综合分析得出新安煤田煤与瓦斯突出具有以小型突出为主、突出前有预兆并受作业方式诱导、突出点附近瓦斯质量体积和瓦斯压力高、易发生在掘进工作面和煤层变化带的特征;分析总结了埋藏深度、瓦斯赋存、地质构造、煤层厚度变化、构造软煤、作业工艺是控制新安煤田煤与瓦斯突出的主要因素,为该煤田防治煤与瓦斯突出提供了理论指导.     

新安煤田煤与瓦斯突出特征及控制因素分析

为了掌握煤与瓦斯突出的特征和控制因素,提高煤矿防突工作的针对性,本文通过统计分析了新安煤田内义煤集团的4个煤与瓦斯突出矿井近年来发生的瓦斯动力现象,综合分析得出新安煤田煤与瓦斯突出具有以小型突出为主、突出前有预兆并受作业方式诱导、突出点附近瓦斯质量体积和瓦斯压力高、易发生在掘进工作面和煤层变化带的特征;分析总结了埋藏深度、瓦斯赋存、地质构造、煤层厚度变化、构造软煤、作业工艺是控制新安煤田煤与瓦斯突出的主要因素,为该煤田防治煤与瓦斯突出提供了理论指导.     

掘进煤巷应力仿真和延时煤与瓦斯突出机理研究

掘进煤巷工作面应力“三带”分布对延时突出起着关键作用．采用岩石破裂过程RFPA^2D分析软件数字仿真了煤巷掘进工作面应力状态及“三带”分布范围，分析了渗透力对瓦斯突出的作用．结果表明：充分卸压带为2m，部分卸压带为2～6m，集中应力带为6～18m．由于掘进工作面煤层应变软化，卸压带宽度随时间延长而展宽；当煤体水平承载能力小于水平载荷时，煤体脱离，在重力作用下冒落、掉渣．此时水平载荷转移到深部煤体，使处于临界状态的深部煤层破坏．这是一个正反馈的加速过程，最后水平载荷形成应力破坏波，造成煤体的快速拉裂破坏，形成煤与瓦斯突出．     

九里山矿14区放顶煤开采瓦斯涌出规律分析

分析了焦作矿务局九里山矿放顶煤工作面沿底掘进及开采期间各生产工序瓦斯涌出规律.与顶分层开采对比,放顶煤开采相对瓦斯涌出量降低,绝对瓦斯涌出量增加倍数小于产量提高倍数,各生产工序以放煤时瓦斯涌出量最大;沿顶掘巷的平均瓦斯涌出量是沿底掘巷的1.25倍,沿底掘进不增加突出危险性.     

煤的孔隙结构与煤岩动力失稳特征的相关性

以冲击倾向性煤层和煤与瓦斯突出煤层作为研究对象,基于压汞法和液氮吸附的实验结果,综合分析了煤样的孔隙结构特征;依据包括煤岩孔隙结构特征在内的物理力学参数,建立了数值模型,从煤层应力分布和应变能的角度讨论了煤的孔隙结构与煤岩动力失稳特征之间的相关性.液氮吸附和压汞实验表明:忻州窑煤样的孔隙主要是开放型孔,赵各庄煤样的孔隙含半开放型孔隙较多,且含有一定量的墨水瓶孔;忻州窑煤样的孔隙含量,尤其是渗流孔隙的含量远大于赵各庄煤样,因此忻州窑煤层中瓦斯更容易释放.数值模型的计算结果表明:在上覆岩层应力和水平应力相同条件下,忻州窑煤层中煤壁附近区域的水平应力比赵各庄煤层低,垂直应力高于赵各庄煤层,煤壁附近的煤体易发生压剪破坏;上覆岩层应力和水平应力相同(6 MPa)时,赵各庄煤层受扰动后应变能密度变化量接近忻州窑煤层应变能密度变化量的2倍,可见赵各庄煤层更易积聚应变能.     

瓦斯压力对煤体冲击指标影响的实验研究

基于突出和冲击地压的主要区别——瓦斯参与程度的不同,从实验的角度出发,利用瓦斯气体密封系统,研究了单轴压缩条件下(有效围压为0)瓦斯对煤体冲击指标的影响规律,提出了鉴别非典型动力灾害的实验方法.结果表明:瓦斯的存在,降低了煤体的冲击倾向性,实验所取煤样在瓦斯压力为0时具备弱冲击倾向,而在2MPa时已无冲击倾向性;但随着瓦斯压力的增加,发生煤与瓦斯突出的几率则不断增加.     

演马庄煤矿突出煤层炮采放顶煤工作面防治煤与瓦斯突出的方法和措施

介绍了演马庄煤矿2702工作面突出煤层炮采放顶煤效果检验的方法和防止煤与瓦斯突出所采取的措施,提出突出煤层炮采放顶煤工作面瓦斯抽放是防止煤与瓦斯突出的有效手段,当工作面有煤与瓦斯突出危险时,采取恰当的防突措施,能够降低煤与瓦斯突出的危险程度,可供同类工作面回采时借鉴.     

红菱煤矿开采保护层对 煤岩体透气性的数值模拟

以红菱煤矿保护层开采为工程实例,通过开采11#煤层,对存在煤与瓦斯突出的7#煤层和12#煤层进行 卸压,利用FLAC3D数值模拟中小同步开挖的渗透率变化情况,对保护层开采过程中煤岩体的渗透性进行了分 析,得出了煤岩体透气性变化规律。结果表明:煤岩体的透气性随着工作面推进不断增强;开采保护层上覆岩体 的渗透率明显比底板岩体的渗透率大;卸压效果越好,渗透率越大。     

Gas-solid coupling laws for deep high-gas coal seams

A better understanding of gas-solid coupling laws for deep, gassy coal seams is vital for preventing the compound dynamic disasters such as rock burst and gas outburst. In this paper, a gas-solid coupling theoretical model under the influence of ground stress, gas pressure, and mining depth is established and simulated by using COMSOL Multiphysics software. Research results indicate that under the influence of factors such as high ground stress and gas pressure, the mutual coupling interaction between coal and gas is much more significant, which leads to the emergence of new characteristics of gas compound dynamic disasters. Reducing the ground stress concentration in front of the working face can not only minimize the possibility of rock burst accidents, which are mainly caused by ground stress, but also can weaken the role of ground stress as a barrier to gas, thereby decreasing the number of outburst accidents whose dominant factor is gas. The results have a great theoretical and practical significance in terms of accident prevention, enhanced mine safety, disaster prevention system design, and improved accident emergency plans.     

Reservoir reconstruction technologies for coalbed methane recovery in deep and multiple seams

Multiple coal seams widely develop in the deep Chinese coal-bearing strata. Ground in situ stress and coal seam gas pressure increase continuously with the increase of the mining depth, and coal and gas outburst disasters become increasingly severe. When the coal is very deep, the gas content and pressure will elevate and thus coal seams tends to outburst-prone seams. The safety and economics of exploited firstmined coal seams are tremendously restricted. Meanwhile, the multiple seams occurrence conditions resulted in different methane pressure systems in the coal-bearing strata, which made the reservoir reconstruction of coal difficult. Given the characteristics of low saturation, low permeability, strong anisotropy and soft coal of Chinese coal seams, a single hydraulic fracturing surface well for reservoir reconstruction to pre-drain the coalbed methane(CBM) of multiple seams concurrently under the different gas pressure systems has not yet gained any breakthroughs. Based on analyses of the main features of deep CBM reservoirs in China, current gas control methods and the existing challenges in deep and multiple seams, we proposed a new technology for deep CBM reservoir reconstruction to realize simultaneous high-efficiency coal mining and gas extraction. In particular, we determined the first-mined seam according to the principles of effectiveness and economics, and used hydraulic fracturing surface well to reconstruct the first-mined seam which enlarges the selection range of the first-mined seam. During the process of mining first-mined seam, adjacent coal seams could be reconstructed under the mining effect which promoted high-efficiency pressure relief gas extraction by using spatial and comprehensive gas drainage methods(combination of underground and ground CBM extraction methods). A typical integrated reservoir reconstruction technology, ‘‘One well for triple use", was detailed introduced and successfully applied in the Luling coal mine. The application showed that the proposed technology could effectively promote coal mining safety and simultaneously high-efficiency gas extraction.     

Rock burst risk evaluation based on equivalent surrounding rock strength

On-site investigations consistently show that the rock burst inherent to coal seams varies greatly with coal seam thickness. In this study, impact factors related to coal seam thickness and surrounding rock strength were analyzed and a corresponding rock burst risk assessment method was constructed. The model reflects the influence of coal seam thickness on the stress distribution of surrounding rock at the roadway. Based on the roadway excavation range, a stress distribution model of surrounding roadway rock is established and the influence of coal seam thickness on rock burst risk is analyzed accordingly. The proposed rock burst risk assessment method is based on the equivalent surrounding rock strength and coal seam bursting liability. The proposed method was tested in a 3500 mining area to find that it yields rock burst risk assessment results as per coal seam thickness that are in accordance with real-world conditions. The results presented here suggest that coal seam thickness is a crucial factor in effective rock burst risk assessment.     

电磁辐射法预测煤与瓦斯突出原理

研究了瓦斯对电磁辐射（ＥＭＥ）的影响规律及影响机制,对电磁辐射法预测煤与瓦斯突出原理进行了探讨,研究结果表明：煤体变形破裂时,电磁辐射与煤岩体的载荷及变形破裂过程密切相关,煤体中的瓦斯能使电磁辐射增强,瓦斯在煤体中的流动及冲击能产生电磁辐射;电磁辐射强度和脉冲数两项指标综合反映了工作面丧方煤体的突出危险程度,用电磁辐射法预测预报煤与瓦斯突出是可行的,煤岩电磁辐射技术在预测煤与瓦斯突出和冲击地压等方     

高瓦斯煤层群保护层开采卸压效果数值模拟

为合理选择保护层,针对高瓦斯突出煤层群安全开采问题,分析了保护层开采的保护作用机理,即保护层开采可对被保护层起到卸压增透作用,改善被保护层的瓦斯抽放效果是解决煤与瓦斯突出问题及瓦斯灾害的重要技术手段;卸压对煤与瓦斯突出及瓦斯问题的解决具有决定作用.针对某矿高瓦斯突出煤层群生产地质条件,采用FLAC3D数值软件模拟2个非突出煤层作为保护层开采时的卸压效果,并对其进行了分析比较,研究结果可为保护层的合理选择提供参考依据.     

Time-domain characteristics of overlying strata failure under condition of longwall ascending mining

Ascending mining is one of the most effective ways to solve problems of water inrush, gas outburst and rock burst in coal seams mining. In order to reveal the law of motion and spatiotemporal relationship of overlaying strata, field measurement has been done in a mine. Long distance drillings were constructed from 4# coal seam to 6# coal seam at several certain typical positions, and movement and failure law of overlying strata after mining was analyzed by drilling video and observing the fluid leakage. Besides, we also analyzed the spatiotemporal development law of overlying strata failure with different mining heights and time intervals in the lower coal seam. The results show that: ascending mining is significantly affected by time-domain characteristics of overlaying strata failure after the lower coal seam’s mining, height equations of caving zone and fractured zone are given in this paper, and the feasibility of ascending mining was compartmentalized concretely according to the spatiotemporal relationship. Research methods and conclusions of this paper have certain referential significance for the study of ascending mining, mining under water, mining under building, mining under railway and stress-relief mining.     

Comparing potentials for gas outburst in a Chinese anthracite and an Australian bituminous coal mine

Gas outbursts in underground mining occur under conditions of high gas desorption rate and gas content, combined with high stress regime, low coal strength and high Young’s modulus. This combination of gas and stress factors occurs more often in deep mining. Hence, as the depth of mining increases, the potential for outburst increases. This study proposes a conceptual model to evaluate outburst potential in terms of an outburst indicator. The model was used to evaluate the potential for gas outburst in two mines, by comparing numerical simulations of gas flow behavior under typical stress regimes in an Australian gassy mine extracting a medium-volatile bituminous coal, and a Chinese gassy coal mine in Qinshui Basin (Shanxi province) extracting anthracite coal. We coupled the stress simulation program (FLAC3D) with the gas simulation program (SIMED II) to compute the stress and gas pressure and gas content distribution following development of a roadway into the targeted coal seams. The data from gas content and stress distribution were then used to quantify the intensity of energy release in the event of an outburst.     

Characteristics and dominant controlling factors of gas outburst in Huaibei coalfield and its countermeasures

In order to master the main characteristics and controlling factors of gas disasters in Huaibei coalfield, based on data analysis, experimental determination and theoretical research, we analyzed the geological evolution and gas parameters in Huaibei mining area. The results show that Huaibei coalfield is located in Xu-Su arcuate tectonic circle, and the coal seam and gas occurrence took on bipolar-distribution. The dominant controlling factors of gas outburst were tectonic structures, tectonic stress, magma intrusion and mining depth. The geological conditions of Huaibei coalfield were very complicated, and almost all the outburst accidents occurred in tectonic structure zones. The horizontal tectonic stress played a dominant role in outburst accident. The thermal evolution and trap effect of magma intrusion controlled the physical characteristics of coal, gas occurrence and outburst. With the increase of mining depth, the possibility of gas outburst accidents increased significantly. After carrying out several effective regional measurements, the gas control effect was obvious and could ensure safety and high efficiency mining in outburst coal seams.