深井软底沿空留巷围岩变形及控制分析

为解决深井软底沿空巷道在高应力环境下变形严重等问题,以杜儿坪矿43209工作面为例,针对围岩变形特征,提出了“超前弱化钻孔+顶板高强锚注+反底拱让压填充+底板注浆+巷旁柔模充填体”的支护方案,通过施工超前工作面弱化钻孔,结合注浆及底板填充让压材料,实现柔性支护。现场试验结果表明,采用优化后的支护方案后,顶板位移量由327 mm减小至108 mm,底板位移量由614 mm减小至149 mm,煤帮位移量由294 mm减小至62 mm,巷道收敛率明显减小,达到了良好的效果。

Domino instability effect of surrounding rock-coal pillars in a room-and-pillar gob

To discuss the domino instability effect and large area roof falling and roof accidents of surrounding rockcoal pillars in a room-and-pillar gob,the equilibrium equation for a roof-coal pillar-floor system with the influence of mining floor was developed based on the engineering conditions of the surrounding rock in a room-and-pillar gob in the 3^(-2)coal seam of Tanggonggou mine.The conditions of system instability and the relationship between system stability and system stiffness were analyzed from an energetic point of view.Numerical simulation using the discrete element software UDEC was also carried out to simulate conditions causing the domino effect on surrounding rock-coal pillars in a 3^(-2)room-and-pillar gob.The results show that:if we want the system to destabilize,the collective energy in roof-and-floor must be larger than that in the coal pillar.When the stiffness of the coal pillars and the roof-and-floor are both greater than zero,the system is stable.When the stiffness of the coal pillars is negative but the summed stiffness of the coal pillars and roof-and-floor is larger than or equal to zero,the system is statically destroyed.When the sum of the coal pillars and the roof-floor stiffness is negative,the system suffers from severe damages.For equal advance distances of the coal mining face,the wider coal pillars can reduce the probability of domino type instability.Conversely,the smaller width pillars can increase the instability probability.Domino type instability of surrounding rock-coal pillars is predicted to be unlikely when the width of coal pillars is not less than 8 m.

Criterion of local energy release rate of gob instability in deep mines considering unloading stress path

The stress path characteristics of surrounding rock in the formation of gob were analyzed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analyzing the instability of deep gob was established based on the mechanism of stress relief in deep mining.The energy evolution law was analyzed by introducing the local energy release rate index(LERR), and the energy criterion of the instability of surrounding rock was established based on the cusp catastrophe theory. The results show that the evolution equation of the local energy release of the surrounding rock is a quartic function with one unknown and the release rate increases gradually during the mining process.The calculation results show that the gob is stable. The LERR per unit volume of the bottom structure is relatively smaller which means that the stability is better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meets the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release,transfer and dissipation and that provided an important reference for the study of the stability of deep mined out area.

Unanticipated multiple seam stresses from pillar systems behaving as pseudo gob–case histories

Underground coal mining in the U.S. is conducted in numerous regions where previous workings exist above and/or below an actively mined seam. Miners know that overlying or underlying fully extracted coal areas, also known as gob regions, can result in abutment stresses that affect the active mining. If there was no full extraction, and the past mining consists entirely of intact pillars, the stresses on the active seam are usually minimal. However, experience has shown that in some situations there has been sufficient yielding in overlying or underlying pillar systems to cause stress transfer to the adjoining larger pillars or barriers, which in turn, transfer significant stresses onto the workings of the active seam. In other words, the overlying or underlying pillar system behaves as a ‘‘pseudo gob." The presence of a pseudo gob is often unexpected, and the consequences can be severe. This paper presents several case histories, summarized briefly below, that illustrate pseudo gob phenomenon:(1) pillar rib degradation at a West Virginia mine at 335 m depth that contributed to a rib roll fatality,(2) pillar rib deterioration at a Western Kentucky mine at 175 m depth that required pillar size adjustment and installation of supplemental bolting,(3) roof deterioration at an eastern Kentucky mine at 400 m depth that stopped mine advance and required redirecting the section development,(4) coal burst on development at an eastern Kentucky mine at 520 m depth that had no nearby pillar recovery, and(5) coal burst on development at a West Virginia mine at the relatively shallow depth of 335 m that also had no nearby pillar recovery. The paper provides guidance so that when an operation encounters a potential pseudo gob stress interaction the hazard can be mitigated based on an understanding of the mechanism encountered.

Optimization of gob ventilation boreholes design in longwall mining

Gob ventilation boreholes(GVBs)are widely used for degasification in U.S.longwall coal mines.Depending on geological conditions,30–50%of methane can be recovered from longwall gob using GVBs.A NIOSH funded research at the Colorado School of Mines confirmed that GVBs can efficiently reduce methane at the face.However,GVBs can also draw some fresh air from the face and create explosive gas zones(EGZs).Explosive gas mixtures may be formed in gob areas due to the increased ingress of oxygen from GVBs.It is critical to identify the locations for GVBs for maximizing extraction of methane and minimizing hazards of explosion.This study analyzes the effect of operating parameters and design of GVB on methane extraction,EGZs formation,and face and tailgate methane concentrations.Methane extraction,formation of EGZs,and concentration of methane in working areas are significantly impacted by various factors.These factors include the distance of work face and tailgate from GVBs,diameter of GVBs,vacuum pressure of wellhead,GVB distance from the roof of the coal seam,and number of operating GVBs in a panel.Computational fluid dynamics(CFD)evaluations suggest optimal design and operating parameters of GVBs that can contribute to maximum benefits with minimum risks.

Temperature field simulation of gob influenced by atmospheric pressure

The current temperature field model of mine gob does not take the boundary conditions of the atmospheric pressure into account, while the actual atmospheric pressure is influenced by weather, so as to produce differences between ventilation negative pressure of the working face and the negative pressure of gas drainage in gob, thus interfering the calculated results of gob temperature field. According to the characteristics of the actual air flow and temperature change in gob, a two-dimensional temperature field model of the gob was built, and the relational model between the air pressure of intake and outlet of the gob and the atmospheric pressure was established, which was introduced into the boundary conditions of temperature field to conduct calculation. By means of analysis on the simulation example, and comparison with the traditional model, the results indicate that atmospheric pressure change had notable impact on the distribution of gob temperature field. The laboratory test system of gob temperature field was constructed, and the relative error between simulated and measured value was no greater than 9.6%, which verified the effectiveness of the proposed model. This work offers theoretical basis for accurate calculation of temperature and prediction of ignition source in mine gob, and has important implications on preventing spontaneous combustion of coal.

采空区瓦斯地面井抽采瓦斯来源及储量预测研究

瓦斯是一种混合气体,主要成分为甲烷。对于瓦斯危害事故的防治、治理以及对于瓦斯资源的有效利用一直以来是困扰全世界煤矿生产单位以及研究学者的一大难题。近年来随着瓦斯抽采技术的不断发展,其作为治理瓦斯危害的有效手段被广泛利用,而准确地预测瓦斯储量是该项工作能顺利进行的基础。本文分析了李村煤矿老采空区的瓦斯赋存状态及分布范围,采空区瓦斯主要来自残留煤柱、遗煤和邻近煤岩层。利用分源预测法,通过建立瓦斯储量计算模型,预测06地面瓦斯抽采井采空区瓦斯最大可采资源量为643.2万m3,实际累计抽采量500余万m3。由地面井(钻孔)实际抽采数据可知,该模型对采空区瓦斯储量做出较为准确的预测,为该矿地面井采空区瓦斯抽采工作奠定了较为可靠的理论基础。

千米深井高地压软岩巷道沿空留巷工程案例

结合朱集东矿深井高地压高瓦斯煤层群条件介绍综采工作面沿空留巷工程案例。采用"三高"锚杆+锚索梁初始支护、锚索梁+注浆超前加固、工字钢梁+铰接顶梁辅助支护、膏体材料泵送充填构筑墙体,有效控制了深部沿空留巷帮部及顶板剧烈变形,在960 m埋深条件下成功留巷2 059 m。巷道掘进至扩刷复用全过程中,帮部以扩容鼓出变形为主,变形量为110~450 mm,顶板以弯曲下沉为主,变形量为257~450 mm,底板以剧烈底臌为主,底臌量为1 311~2 500 mm,墙体以发育竖向裂隙为主,变形量为61~90 mm。取得局部地段卧底即满足复用的良好围岩控制效果。

地面钻井抽采采空区煤层气地质风险评估

从是否有气、能否产气、是否盈利出发,对地面钻井抽采采空区煤层气(简称GD)进行了风险识别;构建了GD风险评估指标体系,并借鉴分段绩点法的思想,提出一种统一不同区块进行GD风险评估时判断矩阵的构建标准。

L型井采空区瓦斯抽采技术的应用

为解决寺河矿3313采煤工作面回采过程中上隅角瓦斯浓度高的问题,运用地面井施工新技术,在3313工作面煤层顶板裂隙带施工一口水平井,利用地面瓦斯抽采泵站通过L型井对采煤工作面的采空区瓦斯进行抽采。地面L型抽采井运行后,平均抽采瓦斯纯量为16.74 m^3/min,瓦斯浓度为70%~90%,日均抽采瓦斯纯量约2.4万m^3。在采煤工作面日产量增加约2 500 t的情况下,回风流中平均瓦斯浓度降低约0.11%。

淮南矿区地面钻井抽采瓦斯技术实践

在应用地面钻井抽采矿井采空区瓦斯的过程中,为了提高地面钻孔的稳定性及瓦斯抽采效果,采用CFD数值模拟和考察试验的方法研究了影响地面钻孔抽采效果和服务期限的不同因素.研究结果表明:地面钻井抽采将很大程度上减小工作面回风流的瓦斯含量,且抽采效果受到煤层条件和钻井位置的制约.通过对试验钻井破坏情况分析,钻井布置在靠近回风巷侧30 m以内,可能会提高钻井的稳定性和服务期限.本文对地面钻井抽采采空区瓦斯技术的推广应用具有重要的指导意义.

深孔爆破在深井坚硬复合顶板沿空留巷强制放顶中的应用

为防止深井坚硬顶板沿空留巷的充填墙体在顶板垮落时被压坏,特采取深孔爆破强制放顶来释放顶板压力以提高沿空留巷的护巷效果。通过数值模拟和理论分析的方法,阐述深孔爆破强制放顶的卸压机制。炸药在坚硬岩体中爆破,爆破孔周边的岩体受爆轰应力波作用产生大量裂隙并发生大幅度位移,使爆破孔周围的应力重新分布,厚层顶板垮落,降低了巷旁充填墙体的附加载荷,从而起到护巷作用。最后,在潘一矿东区1252(1)工作面进行超前深孔爆破强制放顶的现场应用,在经历工作面回采和充填留巷稳定阶段后,墙体整体维护效果良好,对类似条件下沿空留巷强制放顶具有很好的借鉴意义。

成庄煤矿采空区煤层气地面井抽采试验

山西晋城矿区主采3#煤层,一般为大采高高强度回采,由此造成工作面瓦斯涌出量大、瓦斯治理压力大等问题。因此,利用采动卸压作用和采空区瓦斯抽采的运移规律,在成庄煤矿施工了采动区地面抽采试验井抽采本煤层采动影响区和采空区煤层气,并运用地面井逐级优化设计方法对试验井的布井位置、井型结构进行了优化。抽采试验结果表明:采空区瓦斯抽采浓度高达50%以上,有效地降低了工作面瓦斯治理压力,试验效果良好。

余吾煤业公司地面钻井抽采采空区瓦斯技术研究及应用

为解决采空区积聚瓦斯涌向工作面,造成工作面和回风流瓦斯浓度超限难题,潞安集团余吾煤业公司根据矿区自身实际情况将瓦斯治理与采矿技术相结合,在N2105工作面开展地面钻井抽采采动影响煤层及采空区瓦斯试验。结果表明:随着工作面推过钻井距离增大,采空区顶板垮落,顶底板裂隙逐渐发育,观测期间瓦斯浓度由初期的12.2%增长到69.4%,瓦斯纯流量从1.32m3/min上升到13.94 m3/min;1个月内累计抽采纯瓦斯总量30.704万m3,产气平稳阶段瓦斯纯流量在9 m3/min以上共13 d,占总抽采期的41.9%。解决回采工作面瓦斯超限的难题的同时,实现了煤与瓦斯共采。

地面垂直采空区抽采钻井井口连接装置故障处理及改进

本文针对地面垂直采空区抽采钻井井口连接装置初期设计不合理采动后易出现损坏现象,介绍了两种处理方法,同时提出了厚薄煤层两种钻井井口连接装置改进方式。

大采高小煤柱沿空掘巷围岩变形规律研究

为解决大采高小煤柱沿空掘巷支护的技术难题,针对谢桥矿1161（3）轨道顺槽的工程技术条件,对其变形特征和破坏特点进行了分析,并运用FLAC3d软件模拟了轨道顺槽在回采期间的受力情况,最终确立了以高强度预应力锚杆、锚索为核心的围岩强化控制技术,优化了支护形式与参数,加强了肩角的支护强度,并进行了井下矿压监测。研究结果表明：在巷道掘进初期,围岩变形速度快,锚杆索支护体系载荷增长迅速;由于厚底煤释放了部分的能量,巷道顶底板整体变形不大;在高支护强度（0.3-0.5MPa）下,回采期间顶板离层最大值为86mm,得到了很好的控制,达到了预期的支护效果。

一种改进的引入修正矩阵的波束赋行算法

提出了一种改进的引入修正矩阵的波束赋行算法。改进的算法在原有的多波束赋行算法(GOB算法)的基础上,通过引入修正矩阵,纠正业务波束在扇区边缘的指向偏差。理论分析和仿真结果表明改进的算法相比原算法提高了业务波束在扇区边缘的指向准确度,对系统性能有一定的提升。

铁法矿区地面垂直采空区井技术

基于对低透气性煤层顶板受采动影响下的移动规律的研究,铁法矿区于1994年通过联合国UNDP项目率先在国内应用地面垂直采空区钻井进行了技术示范。通过对已经施工的21口采空区钻井的应用和研究,铁法矿区对于采空区钻井的布孔原则和理论方面取得了丰富的经验和成果,大量的实践也证明了地面垂直采空区钻井技术在低透气性煤层,尤其在煤层群开采时,是最有效的煤层气开发技术之一。

6阵元智能天线赋形方法性能测试研究

本文研究蜂窝小区6阵元智能天线在不同场景下的天线赋形增益,及不同智能天线赋形算法的性能。实验测试结果表明,对于6阵元智能天线,采用赋形比不采用赋形方式能得到3～5dB的增益,采用特征分解赋性算法(EBB)比固定波束赋形算法(GOB)增益高1～3dB左右。

深井矸石充填工作面沿空留巷围岩控制原理与技术

深井工作面矿压显现剧烈使得沿空留巷存在诸多困难。采用矸石充填采空区可有效限制深部采场覆岩大范围的破断、运动,缓解深井工作面剧烈的矿压显现,为深井工作面沿空留巷奠定基础。通过现场实测和理论计算探讨了深井矸石充填工作面覆岩运动特征,探讨了沿空留巷围岩承载结构及其稳定性。根据新巨龙煤矿2305S-2号工作面实际情况,设计了以矸石墙+钢管混凝土立柱为主的巷旁支护结构,并提出了留巷顶板超前支护、强力护表、深部锚固,巷旁支护结构合理宽度、侧向约束、协同承载,实体煤帮卸应力、防冲击、控片帮的控制方式,留巷底板高应力深部转移的沿空留巷围岩控制原理和先固顶→再护帮→后控底的沿空留巷围岩控制原则。形成了锚杆+W钢带超前支护和长锚索+注浆锚索永久支护的沿空留巷围岩控制技术,成功实现了新巨龙煤矿2305S-2号深井矸石充填工作面沿空留巷。沿空巷道围岩实测发现留巷矸石墙变形不均匀,承载能力增长缓慢,钢管混凝土立柱钻底,顶板锚索易破断等问题。需要进一步加强留巷矸石墙的侧向约束,提高矸石墙承载能力。钢管混凝土立柱底部安装大垫板,控制立柱钻底量,沿空留巷顶板锚索要求具备一定的延伸率,实现长锚索与顶板围岩的协同变形与承载。