Layout and support design of a coal roadway in ultra-close multiple-seams

A roadway within ultra-close multiple-seams(RUCMSs) is one of the most difficult supported coal roadways to deal with in underground coal mines. This is usually due to the unknown stress distributions, improper roadway layout, and unreasonable support parameters. In order to solve this support problem and effectively save RUCMSs from frequent and abrupt disasters(such as serious deformation of the surrounding rock, roof cave ins, and coal side collapse), a comprehensive method is adopted here which includes theoretical analysis, numerical simulation, and field monitoring. A mechanical model was constructed to determine the stress distribution in the coal pillar after two sides of a longwall panel had been mined. Based on this model, the horizontal, vertical, and tangential stress equations for the plane below the floor of the upper-left coal pillar were deduced. In addition, a typical coal mine(the Jinggonger colliery, located in Shuozhou city, Shanxi province, China) with an average distance between its 9# and 11# coal seams of less than 8.0 was chosen to conduct research on the proper layout and reasonable support required for a typical coal roadway located within coal seam 11#. Using FLAC3D(Fast Lagrangian Analysis of Continua in 3-Dimensions) numerical software, eight schemes were designed with different horizontal distances(d) between the center lines of the coal pillar and the roadway in the lower coal seam(RLCS). The simulations and detailed analysis indicate that the proper distances required are between 22.5 and 27.5 m. A total of 20 simulation schemes were used to investigate the factors influencing the support provided by the key bolts(bolt length, spacing, distance between two rows, installation angle, and pre-tightening force). The results were analyzed and used to determine reasonable values for the support parameters. Field results show that the stability and strength of the RLCS can be effectively safeguarded using a combination of researched stress distribution characteristics, proper layout of the RLCS, and correct support parameters.

Numerical simulation and experiment analysis of improving permeability by deep-hole presplitting explosion in high gassy and low permeability coal seam

Created a new damage model for explosive for LS-DYNA3D,taking advantageof the Taylor method aimed at the high gassy and low permeability coal seam,and numericallysimulated and analyzed the deep-hole presplitting explosion.The entire processof explosion was represented,including cracks caused by dynamic pressure,transmissionand vibration superposition of stress waves,as well as cracks growth driven by gas generatedby explosion.The influence of the cracks generated in the process of explosion andthe performance of improving permeability caused by the difference of interval between.explosive holes were analyzed.A reasonable interval between explosive holes of deepholepresplitting explosions in high gassy and low permeability coal seams was proposed,and the resolution of gas drainage in high gassy and low permeability coal seam was putforward.

A Numerical Investigation of the Stress Relief Zones Around a Longwall Face in the Lower Seam for Gas Drainage Considerations

Extraction of a protective coal seam (PVCS)-below or above a coal seam to be mined with the potential of coal andgas outburst risk-plays an important role not only in decreasing the stress field in the surrounding rock mass but alsoin increasing the gas desorption capacity and gas flow permeability in the protected coal seam (PTCS). The PVCSis mined to guarantee the safe mining of the PTCS. This study has numerically evaluated the stress redistributioneffects using FLAC3D model for a longwall face in Shanxi Province. The effects of mining depth, mining height andinter-burden rock mass properties were evaluated using the stress relief angle and stress relief coefficient. Verticalstress distribution, stress relief angle and stress relief coefficient in the PTCS were analyzed as the face advancedin the PVCS. The results showed that the stress relief achieved in different locations of the PTCS varied as the faceadvanced. Sensitivity analyses on the pertinent variables indicate that the stress relief in the PTCS is affected mostby the mining depth followed by the inter-burden lithology and the mining height. Furthermore, the elastic moduliof different layers within the inter-burden rock mass are more important than their uniaxial compressive strength(UCS) and Poisson’s ratio. These observations can guide gas drainage borehole design to minimize the accidentsof coal and gas outbursts.

地面井分层卸压的煤系气合采原理及方式探讨

为了进一步认识制约煤系气合采的因素,提高煤系合层排采各产层的产气贡献,分别从动力、通道和气源条件出发,分析了煤系气合采的必备因素。基于改变地应力状态提高储层导流能力以及分层改变储层流体压力,满足多层合采动力条件的原理,提出了地面井分层卸压的煤系气合采方式。该方式通过在地面进行定向钻井,在目标储层中进行高压水射流作业,人工创造卸压空间(缝、槽、穴等),改变地应力状态,降低有效应力伤害,增加储层导流通道的数量和开度,提高目标储层压降传递速率。待储层压力降至符合煤系气合采动力条件时进行合层排采,从而提高煤系合采各产气层的产气贡献。相较于常规增产改造措施,此方式能够减少煤系气储层在有效应力作用下的储层伤害,且有助于提高储层压降传递效率,增强煤系气的解吸和扩散,降低多层煤系气合采过程中的层间干扰。在以上研究基础上,认为地面井分层卸压的合采方式主要适用于储层地应力大、产层间距小的煤系气储层,且有望在薄互层煤系气储层增产改造及层间干扰严重的叠合共生煤系储层开发领域进行应用推广。

浅埋多煤层群协调绿色开采关键技术研发与实践

西部矿区多煤层赋存条件导致了“采面布局矛盾、覆岩结构多变、地表运移叠加”的突出性、普遍性问题,探索适应多煤层高强度开采的协调绿色开采技术成为西部矿区多煤层安全、高效开采的关键。针对浅埋厚煤层群高强度开采面临的主要技术难题,从多煤层开采时空布局、工作面岩层稳定性控制、重复扰动下的地表沉陷等方面,系统地阐述了浅埋多煤层群协调绿色开采的几项关键技术。研究结果如下:(1)揭示了西部多煤层高强度开采层间相互作用机理,构建了多煤层重复开采扰动定量判据与评价方法,创新提出了以层间最小扰动为目标的“薄、中、厚”煤层交错分布协调开采技术;(2)提出了多煤层工作面岩层稳定控制技术,建立了全覆岩结构破断模型,揭示了全覆岩结构破断条件下的支架与围岩相互作用规律,在此基础上针对多煤层开采工作面支护在不同的位置需要采用不同支护策略的需求,研发了工作面支架抗冲双伸缩立柱和超前巷道支护状态监测系统,实现工作面多区域安全高效稳定支护;(3)通过揭示浅埋多煤层斜交叠置开采下地表动态移动特征和地表裂缝发育规律,给出地表下沉系数的确定方法,研发了塌陷区裂缝“土壤重构–原位充填–微地形改造”组合的治理关键技术,有效防治黄土沟壑区的采煤地表塌陷。上述核心技术在张家峁、柠条塔、红柳林等20余个大型煤矿成功应用,为我国西部矿区高质量、可持续开发提供了技术支撑。

深部高瓦斯煤层爆破致裂增透裂纹扩展规律研究

针对深部高瓦斯煤层在地应力作用下爆破增透时裂纹扩展规律尚不明确的问题,首先根据爆破应力波的传播和叠加,从理论上分析了地应力和爆破荷载耦合作用下炮孔周围的应力分布规律;然后通过室内试验研究了不同地应力条件下单孔爆破裂纹扩展特征,在此基础上,对不同侧压系数下双孔爆破裂纹扩展机理以及贯通过程进行数值模拟研究,并结合ImageJ图像识别软件和LS-Pre-Post软件,以裂纹密度和扩展长度为量化指标表征地应力对裂纹发育程度的影响;最后根据室内试验和数值模拟研究结果,给出考虑地应力影响下的煤层爆破致裂增透爆破孔布置方案建议。单孔爆破室内试验结果表明:地应力可以减小爆破荷载引起的拉应力,从而抑制裂纹扩展;在非静水地应力条件下,与较大主应力方向正交的拉应力受到削弱,导致该方向的裂纹扩展受到抑制,使裂纹优先向高应力方向扩展;双孔爆破数值模拟研究结果表明:侧压系数不为1时,爆生裂纹扩展呈现出方向性,主裂纹倾向于向较高地应力方向扩展,造成爆破裂纹区域呈椭圆形,长轴和较大地应力方向一致。根据室内试验和数值计算结果,在深部煤层进行爆破致裂增透时,宜沿较大地应力方向钻孔,有利于提高爆破致裂增透效果。研究成果对深部高瓦斯煤层爆破增透时了解裂纹扩展机理以及优化炮孔布置方案具有指导意义。

近距离煤层群多重采动覆岩破坏特征及应力传递规律研究

近距离煤层群开采覆岩破坏特征不同于单层煤开采,同时存在层间相互影响的问题。以晋能控股煤业集团燕子山煤矿11#煤层、14-2#煤层、14-3#煤层三层近距离煤层为研究对象,通过进行物理相似模拟实验和数值模拟计算,研究分析了近距离煤层群开采时顶底板围岩的覆岩破坏特征及应力传递规律。研究结果表明:近距离煤层群下行开采过程中,随着采动次数增加,顶板横向裂隙超前发育和纵向裂隙穿层效果更为明显,垮落块度明显减小,来压规律不明显;煤层顶板覆岩因采动产生的应力峰值随采动次数增加而降低;初次采动影响下,稳定后的覆岩应力要明显小于原岩应力,而多次采动稳定后的覆岩应力与该次采动前相近;上覆岩层在多重采动影响下,破坏更彻底,形成台阶式的岩层切落。研究结果可为条件相似的近距离煤层群开采顶底板围岩控制、采空区积水及瓦斯防治提供参考依据。

Experimental Simulation on Dynamic Variation of the Permeability of High-Rank Coal Reservoirs

In terms of the coal reservoir permeability of effective stress, coal matrix shrinkage and gas slippage,we conduct the tests of gas permeability under constant confining pressure and effective stress, as well as illustrate the cumulating method of permeability increment caused by the effects of gas slippage and coal matrix shrinkage.The results show that under the constant confining pressure, gas slippage affecting coal permeability changes to effective stress affecting it mainly. The change point increases with the increase of the confining pressure. The gas slippage effect leads to high permeability under low confining pressure, but coal matrix expansion results in the low value as confining and gas pressures increase. Combined with the drainage process of coalbed methane(CBM)well, the permeability is divided into four change stages based on the above analysis about the three effects, which can improve the change regulation understanding. Four stages are the downward phase under effective stress,the conversion phase of effective stress-coal matrix contraction effect(mainly based on effective stress), the rising stage of the effective stress-coal matrix contraction effect(mainly based on coal matrix contraction effect) and the rising phase of coal matrix contraction-slippage effect(mainly based on slippage effect). Permeability of coal reservoir during the process of drainage and production goes through four stages.

高应力软弱厚煤层沿空巷道矿震风险控制

矿震是深部高应力回采巷道失稳的重要原因,以余吾煤业N2106回风巷为例,开展了高应力软弱厚煤层沿空巷道矿震风险控制研究,研究结果表明:(1)巷道对回采扰动的敏感性极强,最大影响范围为397 m。(2)大能量微震事件密集分布于巷道煤柱帮侧围岩,巷道底煤和两帮是容易出现破坏的部位。(3)巷道失稳破坏的临界应力条件为18.41 MPa,单位长度巷道煤体释放能量为2.29×10^(6)J,顶板释放最大能量为8.6×10^(7)J。(4)提出采用应力和能量的协同控制策略对矿震进行防治设计。

金达煤业9、10号煤层耦合高应力场回采巷道支护研究

金达煤业9、 10号煤层属于近距离煤层,上覆9号煤层基本采空,9号煤层的开采活动导致10号煤层顶板的完整性受到了严重的破坏,由于9号煤层开采形成的保护煤柱在其底板的一定范围内形成了集中应力,从而导致10号煤层工作面顶板极易冒落,且支护困难。因此,针对近距离煤层的开采,探讨了耦合高应力场的巷道支护方式及其参数,提高了矿井生产的安全性。

多煤层复合采动顶底板裂隙带发育规律研究

基于友众煤矿多煤层复合采动顶底板裂隙发育情况,分别采用理论计算、数值模拟和钻孔实测等方法进行研究,计算统计出150202工作面顶板垮落带发育高度分别为40.11~63.09 m、50.2 m、54~57 m,3种方式结果变化范围基本一致。结合矿井地质条件和研究结果可知,15号下煤层采动裂隙带在无构造区域内不会导通上覆3号、6号含水层,在贯穿性断层或陷落柱赋存区域内存在联通导水的可能性。因此,煤矿制定“物探先行、钻探验证、查清构造、上防下采”的防治水原则,为相关类型矿井生产提供依据。

近距离煤层采空区下巷道支护优化设计

针对双马一矿12201运输巷变形破坏严重的问题,结合双马一矿11号和12号近距离煤层实际赋存环境,运用FLAC3D软件分析掘巷、工作面回采围岩应力演化规律。模拟结果显示,在掘巷期间两帮出现不对称应力升高区。工作面回采稳定后,运输巷采空区帮转为应力降低区,而实体煤帮在多重扰动作用下,巷帮侧向支承压力明显升高。根据模拟结果对巷道支护进行优化设计,巷帮采用全锚索支护并且增加锚杆索支护密度。现场实测表明,两帮围岩变形100 d内稳定在300 mm,顶板变形量稳定在200 mm,优化支护方案明显减少了巷道围岩变形量,巷道锚固圈稳定,有效控制围岩变形。

近距离高应力强突煤层群工作面区域瓦斯联合高效治理技术研究与应用

近距离高应力强突煤层群主要受地应力主导的复合动力灾害影响,另加上层理紊乱、煤质极其松软的软分层,极大增加了深部强突煤层诱导煤与瓦斯突出的风险。现如水力冲孔、机械造穴等常规的增透技术,存在着影响范围小、衰减速度快、工作量繁重等缺陷,这导致瓦斯治理工程量大、瓦斯治理成本高且整体瓦斯治理效果较差,严重制约着矿井的生产接替。为解决深部强突煤层群瓦斯治理难题,该文以平衡或消除地应力为切入点,在平煤股份一矿回采区域引入高压注水增透技术。通过工程实践发现,高压注水增透后有效影响半径为26 m以上;平均单孔抽采纯量提高了12.6倍。该工程实践可为近距离高应力强突煤层群瓦斯高效治理技术提供参考。

Coalbed methane desorption characteristics controlled by coalification and its implication on gas co-production from multiple coal seams

In this work,CH4 isothermal adsorption measurements were carried out on 64 coal samples collected from western Guizhou Province of China,and the coalbed methane(CBM)desorption processes were quantitatively analyzed.The results show that the Langmuir volume and the Langmuir pressure are controlled by coalification,and tend to increase as the vitrinite reflectance changes from 0.98% to 4.3%.Based on a division method of CBM desorption stages,the CBM desorption process were divided into four stages(inefficient,slow,fast and sensitive desorption stages)by three key pressure nodes(the initial,turning and sensitive pressures).The fast and sensitive desorption stages with high desorption efficiency are the key for achieving high gas production.A theoretical chart of the critical desorption pressure(P_(cd))and its relationship with different pressure nodes was established.The higher-rank coals have the higher initial,turning and sensitive pressures,with larger difference between pressure nodes.Most CBM wells only undergo partial desorption stages due to the differences in P_(cd) caused by the present-gas content.Under the same gas content conditions,the higher the coal rank,the less desorption stages that CBM needs to go through.During coalbed methane co-production from multiple coal seams within vertically superposed pressure systems,the reservoir pressure,the P_(cd),the initial working liquid level(WLL)height,and coal depth are key factors for evaluating whether coal seams can produce CBM simultaneously.It must be ensured that each production layer enters at least the fast desorption stage prior to that the WLL was lower than the depth of each layer.Only on this basis can all layers achieve the maximum gas production.

高应力区软岩煤层巷道掘进支护优化

基于长平煤矿53101巷掘进期间受地质构造应力影响,围岩出现破碎、巷帮垮落现象,分析了围岩破碎机理,对垮落巷帮采取柔性注浆加固技术,对顶板采取“桁架锚索+L型拉棚+梯形钢棚”联合支护,从现场实际应用效果来看,通过对巷帮及顶板采取联合支护技术后,提高了巷道围岩稳定性,两帮最大收缩量为0.32 m,顶底板移近量为0.21 m,取得了显著应用成效。

抽采瓦斯过程中煤层瓦斯压力演化规律的物理模拟试验研究

利用自主研发的多场耦合煤层气开采物理模拟试验系统,开展了不同地应力水平下抽采瓦斯的物理模拟试验,对抽采瓦斯过程中煤层瓦斯压力演化规律进行了探讨。结果表明:1在抽采瓦斯过程中,煤层瓦斯压力在初期降低较快后期降低缓慢,并且距钻孔越近,瓦斯压力下降速度越快,而与距钻孔出口的距离无关;2在与抽采钻孔垂直的断面瓦斯压力场中,等压线以钻孔为中心呈现圆环形分布,在与抽采钻孔平行的纵面和层面瓦斯压力场中,等压线则以钻孔为对称轴呈现漏斗形分布,且距钻孔及钻孔出口越近瓦斯流速越大;3地应力的增加降低了煤层渗透率,阻碍了瓦斯的运移,使抽采过程中瓦斯压力的降低速度变慢,瓦斯流速减小。

地应力对煤储层渗透性影响及其控制机理研究

针对地应力对煤储层初始渗透性及水力压裂裂缝扩展研究,从煤储层地应力状态影响因素、地应力对渗透率的影响规律及控制机理方面进行分析,总结了国内外地应力对煤储层渗透性影响规律及机制研究的最新进展。研究结果表明:煤储层地应力状态影响因素包括构造作用、埋藏深度和煤岩类型3个方面,其中构造作用和埋藏深度占据主导地位。目前捕获地应力大小多利用水压致裂法和物理试验测试,当前主要研究了现代地应力场特征、实验室模拟、数值模拟不同地应力对煤储层渗透率影响,其实质是对煤储层孔隙-裂隙结构产生变形。区域应力场产生区域性的裂隙系统,控制着煤储层渗透性区域性分布,而局部构造地带控制着不同区块渗透率的非均质性分布。渗透率随着有效垂直应力、有效最大水平主应力和有效最小水平主应力增加均呈负指数减小。相对于地应力差,应力差系数才是影响水力裂缝沿着最大主应力方向扩展的主要因素。

上保护层开采下煤岩强扰动力学行为与渗透特性

保护层开采在低渗透高瓦斯近距离煤层中得到广泛应用,研究保护层开采扰动下的煤岩强扰动力学行为与渗透特性为进一步更加高效安全的开采被保护层煤层提供了理论支持。选取平煤集团十二矿上保护层己14煤层工作面己14-31010和被保护层己15煤层工作面己15-31030为研究对象,进行相似模拟试验和保护层开采过后被保护煤层受力分析。通过相似材料模拟试验获取保护层开采方式下被保护层的受力情况,上保护层开采过程中,煤层压力先增大后减小,采空区重新压实稳定后,应力状态近似恢复到原岩应力状态。通过对保护层开采后的被保护煤层受力分析获取煤层变形后的应力状态,上保护层开采过后,被保护层煤层产生变形,煤层上部分膨胀变形,应力小于原岩应力;下部分煤层压缩,应力大于原岩应力。结合二者的结果获取保护层开采方式下室内试验中被保护层煤层应力加载路径。依据被保护层煤层应力加载路径,设计进行采动耦合应力路径下的煤样渗流试验。试验结果表明:上保护层煤层开采过程中,同等试验条件下,被保护层煤层可承受的上保护层开采扰动应力越大,被保护层煤层开采过程中的煤体破坏应力峰值越大,体积应变越大;被保护层煤层开采过程中,M组煤样和N组煤样应力应变曲线与常规保护层卸荷三轴试验相比,扩容点出现位置明显提前;同等应力状态下,水压越大,煤样的体积应变越大;被保护层煤层开采过程中,M组煤样初始围压为35MPa,围压对渗透率的影响大于轴压的影响,N组煤样初始围压为20MPa,围压、轴压交替对渗透率产生主要影响,渗透率曲线呈现“W”型。两组试验中,扰动应力最大的试样破坏前的渗透率普遍大于其他试样的渗透率。

高瓦斯低透气性煤层深孔预裂爆破增透数值模拟

针对高瓦斯低透气性煤层,采用Taylor方法建立了一个新的LS-DYNA3D爆破损伤模型,对深孔预裂爆破进行了数值模拟研究,再现了爆破过程中,动压冲击震裂、应力波传播与叠加以及爆生气体驱动裂纹扩展的整个过程,分析了爆破孔间距对爆生裂纹和爆破增透效果的影响,提出了高瓦斯低透气性煤层深孔预裂爆破的合理间距为5-6 m,为高瓦斯低透气性煤层的瓦斯抽放提出了解决方案.

黔西多煤层气井递进排采与分隔排采工艺探讨

为了研究黔西多煤层地区递进排采的条件和工艺,提高煤层气井单井产量,基于上二叠统多层叠置含气系统典型煤层气井试井和实测参数,通过设置储层物性变参数序列、定参数序列和基本参数序列,利用COMET3软件数值模拟计算了各方案的产气量、产水量,通过定义递进排采10年累计产气量与主采层单采累计产气量的比值,得出各含气系统适合递进排采的储层压力、渗透率、含气量、孔隙度的临界差值分别为1.14 MPa、1.31×10-3μm2、11.33 m3/t、0.042;递进排采工艺先从下至上套管压裂首排系统和次排系统,系统之间放置封隔器,后排系统采用高能气体处理或其他非压裂改造工艺;设计了多煤层分隔合排工艺,通过增加悬挂套管、连通管实现"气走气路、水走水路",从而避免层间干扰;数值模拟结果表明,6、16、23号煤层10年内分隔合采累计产气量较递进排采有大幅增加。