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.

Technique of coal mining and gas extraction without coal pillar in multi-seam with low permeability

Aimed at the low mining efficiency in deep multi-seams because of high crustalstress,high gas content,low permeability,the compound 'three soft' roof and the trouble-somesafety situation encountered in deep level coal exploitation,proposed a new idea ofgob-side retaining without a coal-pillar and Y-style ventilation in the first-mined key pressure-relieved coal seam and a new method of coal mining and gas extraction.The followingwere discovered:the dynamic evolution law of the crannies in the roof is influenced bymining,the formative rule of 'the vertical cranny-abundant area' along the gob-side,thedistribution of air pressure field in the gob,and the flowing rule of pressure-relieved gas ina Y-style ventilation system.The study also established a theoretic basis for a new miningmethod of coal mining and gas extraction which is used to extract the pressure-relievedgas by roadway retaining boreholes instead of roadway boreholes.Studied and resolvedmany difficult key problems,such as,fast roadway retaining at the gob-side without a coalpillar,Y-style ventilation and extraction of pressure-relieved gas by roadway retainingboreholes,and so on.The study innovated and integrated a whole set of technical systemsfor coal and pressure relief gas extraction.The method of the pressure-relieved gasextraction by roadway retaining had been successfully applied in 6 typical working faces inthe Huainan and Huaibei mining areas.The research can provide a scientific and reliabletechnical support and a demonstration for coal mining and gas extraction in gaseous deepmulti-seams with low permeability.

Research into comprehensive gas extraction technology of single coal seams with low permeability in the Jiaozuo coal mining area

For a low permeability single coal seam prone to gas outbursts, pre-drainage of gas is difficult and inefficient, seriously restricting the safety and efficiency of production. Radical measures of increasing gas extraction efficiency are pressure relief and infrared antireflection. We have analyzed the effect of mining conditions and the regularity of mine pressure distribution in front of the working face of a major coal mine of the Jiaozuo Industrial （Group） Co. as our test area, studied the width of the depressurization zone in slice mining and analyzed gas efficiency and fast drainage in the advanced stress relaxation zone. On that basis, we further investigated and practiced the exploitation technology of shallow drilling, fan dril- ling and grid shape drilling at the working face. Practice and our results show that the stress relaxation zone is the ideal region for quick and efficient extraction of gas. By means of an integrated extraction technology, the amount of gas emitted into the zone was greatly reduced, while the risk of dangerous outbursts of coal and gas was lowered markedly. This exploration provides a new way to control for gas in working faces of coal mines with low permeability and risk of gas outbursts of single coal seams in the Jiaozuo mining area.

Hydraulic drill hole reaming technology with large flow and draining of coal mine gas

This paper takes Zhaozhuang mine in Shanxi province as an example to study the technology of hydraulic reaming drill hole for improving the gas extraction.The influence of the physical properties of coal seam on the hydraulic reaming drill holes and the draining of coal mine gas were analyzed and discussed for different coal structure areas,and the following conclusions were made.Hydraulic drill hole reaming has had a positive impact in Zhaozhuang Mine,and can improve the efficiency of gas extraction to different degrees.The water jet pressure used in hydraulic drill hole reaming mainly depends on the structure of the coal.When the coal seam basically becomes integrated,the critical water jet pressure increases,the discharge becomes relatively easy to achieve,the blocking effect on the gas extraction decreases,and the gas extraction significantly increases after the reaming process.When the coal seam is broken,the critical water jet pressure decreases,the discharge becomes difficult to achieve,the blocking effect on the gas extraction becomes obvious,and the gas extraction changes slightly after reaming.

Progress on the hydraulic measures for grid slotting and fracking to enhance coal seam permeability

A method of hydraulic grid slotting and hydraulic fracturing was proposed to enhance the permeability of low permeability coal seam in China. Micro-structural development and strength characteristics of coal were analysed to set up the failure criterion of coal containing water and gas, which could describe the destruction rule of coal containing gas under the hydraulic measures more accurately. Based on the theory of transient flow and fluid grid, the numerical calculation model of turbulence formed by high pressure oscillating water jet was used. With the high speed photography test, dynamic evolution and pulsation characteristics of water jet water analysed which laid a foundation for mechanism analysis of rock damage under water jet. Wave equation of oscillating water jet slotting was established and the mechanism of coal damage by the impact stress wave under oscillation jet was revealed. These provide a new method to study the mechanism of porosity and crack damage under high pressure jet.Fracture criterion by jet slotting was established and mechanism of crack development controlled by crack zone between slots was found. The fractures were induced to extend along pre-set direction,instead of being controlled by original stress field. The model of gas migration through coal seams after the hydraulic measures for grid slotting and fracking was established. The key technology and equipment for grid slotting and fracking with high-pressure oscillating jet were developed and applied to coal mines in Chongqing and Henan in China. The results show that the gas permeability of coal seam is enhanced by three orders of magnitude, efficiency of roadway excavation and mining is improved by more than 57%and the cost of gas control is reduced by 50%.

低透气性煤层高压脉冲射流割缝-压裂增透技术应用研究

针对盘州平关镇大坪煤矿18采区20号煤层复杂地质条件及瓦斯抽采难题,提出一种高压脉冲射流割缝导向压裂增透技术。为验证该技术效果,分析了其增透技术机理,并设计了4种试验方案进行对比分析。结果表明,采用高压脉冲射流割缝导向压裂方案在瓦斯抽采效果方面显著优于其他方法,与普通抽采、高压脉冲射流割缝、高压水力压裂抽采瓦斯相比,其平均每日抽采瓦斯浓度分别提高了3.01倍、1.41倍和1.67倍;平均每日抽采瓦斯纯流量也相应提升了2.86倍、1.42倍和1.62倍。经过90 d的抽采,该方案的抽采影响半径达到了5.06 m,分别为普通抽采、高压脉冲射流割缝和高压水力压裂抽采方案的2.56倍、1.25倍和1.29倍;在抽采效果相同的条件下,钻孔施工时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了60%、32%和20%,瓦斯抽采达标所需时间分别比普通抽采、高压脉冲射流割缝和高压水力压裂方案缩短了70%、50%和62%。高压脉冲射流割缝导向压裂技术对低透气性煤层瓦斯治理效果较为理想,可供类似矿井借鉴。

利用CO_(2)气相压裂技术提高煤层透气性:以吉宁煤矿为例

为破解复杂低渗高瓦斯煤层瓦斯治理技术难题,本文以山西华晋吉宁煤矿2号煤层2203工作面为研究对象,通过采取CO_(2)气相压裂增透技术,对4组(共12个)抽采钻孔的瓦斯抽采浓度和瓦斯抽采纯量进行分析,得出有效致裂影响范围,进一步评价瓦斯抽采效果和防突效果。结果表明:该地质单元的有效致裂裂缝影响范围为6~7 m;常规抽采孔的瓦斯抽采纯量为0.018 m^(3)/min,与其相比,4组抽采钻孔百米瓦斯抽采纯量平均值为0.179 m^(3)/min,提升了8.9倍;在衰减区域,瓦斯抽采浓度均值64.7%、纯量均值0.150 m^(3)/min,在稳定区浓度,瓦斯抽采均值为73.2%、纯量均值0.188 m^(3)/min,相比稳定区域瓦斯抽采参数更高。该技术有效增大了2号煤层的透气性,提高了瓦斯抽采效率和煤巷掘进速度,减少了钻孔施工投入,缓解了采掘接替紧张的局面。

煤与远程卸压瓦斯安全高效共采试验研究

运用高瓦斯煤层群煤与瓦斯安全高效共采的思想,在淮南潘一矿进行了煤与瓦斯安全高效共采及远程瓦斯抽采的试验研究:首先开采瓦斯含量低、无突出危险的B11煤层,利用其采动影响使处在其上部70m(相对层间距35)的C13煤层卸压,煤层透气性系数增加近3000倍,瓦斯大量解吸并形成了沿顺层张裂隙流动的条件.通过在C13煤层底板沿走向布置的瓦斯抽采巷向C13煤层均匀地打网格式上向穿层钻孔,C13煤层内的卸压解吸瓦斯在煤层残余瓦斯压力和抽采负压作用下沿顺层张裂隙向抽采钻孔汇集,瓦斯抽采率达60%以上,不仅消除了煤与瓦斯突出危险性,而且相对瓦斯涌出量由原来25m3/t下降到5m3/t,工作面日产量由原来的1700t提高到5100t,成功地实现了煤与瓦斯两种资源的安全高效共采.

低透气性煤层群高瓦斯采煤工作面强化抽采卸压瓦斯机理及试验

针对低透气性高瓦斯煤层群首采卸压层瓦斯涌出量大、瓦斯治理困难的现实条件,在模型试验和理论研究的基础上,揭示出煤层群首采关键卸压层开采后采动影响区内顶、底板岩层裂隙的动态演化规律和卸压瓦斯运移规律,发现采空区侧存在"竖向裂隙发育区",弯曲下沉带和底板膨胀变形带内煤体发生膨胀变形,煤层的透气性显著增加。2371(1)工作面煤气共采实践表明,工作面最大绝对瓦斯涌出量70.46m3/min,平均56.71m3/min,瓦斯抽采率达85.2%,其中抽采的高浓度瓦斯比例为67.25%,抽采的低浓度瓦斯比例为32.75%,保证工作面的安全回采,实现了煤与瓦斯安全高效开采。

高压脉冲水射流提高松软煤层透气性的研究

提出了利用高压脉冲水射流钻孔、切缝以提高松软煤层透气性和瓦斯抽采率的新思想.基于岩石动态损伤模型,理论分析和数值模拟了高压脉冲水射流瞬时动载荷、柔性撞击作用下煤体的动态损伤特性及裂隙场的变化规律.结果表明,高压脉冲水射流的冲击效应、剥蚀效应以及震动效应等冲击荷载作用可有效破碎煤体,增大煤体裂隙率和裂隙连通率,提高煤层透气性.研发出了低透气性煤层中的高压脉冲水射流瓦斯抽采系统,在重庆某典型高瓦斯低透气性煤矿进行了成功应用,应用结果表明,高压脉冲水射流有效提高了煤层透气性,平均百米钻孔煤层瓦斯抽放量较原工艺提高了7.8倍.

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.

注气驱替抽采瓦斯技术在高瓦斯突出矿井煤巷掘进中的试验

对于低透气性突出煤层采用常规瓦斯抽采方法，掘进速度较慢。通过分析注空气对瓦斯抽采钻孔增流、煤层瓦斯驱替，以及煤层增透的多重效应，结合山西某矿掘进工作面实际条件，分析了掘进工作面注气驱替强化抽采瓦斯技术及其试验效果。现场实践表明：注气后瓦斯抽采纯量为注气前的1.04～9.44倍，工作面措施效果检验指标KhAh2值分别降低了9．7％和18．1％，月进度提高了110．7％，可为低透气性突出煤层巷道安全快速掘进提供参考。

煤层群煤与瓦斯安全高效共采体系及应用

提出了高瓦斯煤层群煤与瓦斯安全高效共采的概念:在煤层群开采条件下,首先开采瓦斯含量低、无突出危险的首采煤层,利用其采动影响使处在其上部和下部的煤层卸压,煤层透气性成百倍地增加,从而形成高效的瓦斯抽采条件,同时进行的卸压瓦斯高效抽采既解决了由卸压煤层向首采煤层涌出瓦斯问题,保障首采煤层实现安全高效开采,又大幅度地降低了卸压煤层的瓦斯含量,消除了煤与瓦斯突出危险性,为在卸压煤层内实施快速掘进与高效采煤方法提供了安全保障,从而实现了瓦斯与煤炭两种资源的安全高效共采,文中介绍了针对不同卸压瓦斯流动特点的近程、中程和远程卸压瓦斯抽采方法及工程应用实践,最后对高瓦斯煤层群煤与瓦斯安全高效共采体系的应用前景进行了分析。

煤矿瓦斯抽采水胶药柱在煤层深孔爆破中的研究与应用

针对高瓦斯低透气性煤层,从理论上探讨了煤矿瓦斯抽采水胶药柱在煤层深孔中爆破时,炸药爆炸冲击波初始峰值压力和传播到孔壁处的入射压力以及孔壁煤面上的透射冲击压力。建立了炮孔周围煤体中的动态应力场,分析了爆源区径向裂隙区的形成和扩展半径。最后将裂隙区半径应用于煤层爆破孔和抽采孔布置参数设计,提出了高瓦斯低透气性煤层深孔预裂爆破孔和瓦斯抽采孔的合理间距,并进行工程实践。结果表明该方法为高瓦斯低透气性煤层增透,进而为解决煤层瓦斯抽采提供了一条有效的解决方案。

高瓦斯低透气性煤层水力压裂数值模拟研究

针对高瓦斯低透气性煤层,采用RFPA2D-Flow软件,对水力压裂进行了数值模拟研究,再现了水力压裂过程中压裂孔周围裂纹的生成和扩展、渗透性和应力的变化。模拟结果表明:压裂过程中,裂纹规模和剪应力随着注水压力的不断增加而增大,并且剪应力的增加随着钻孔周围裂纹的扩展不断远离压裂孔,压裂孔周围的渗透性有了很大程度的提高,最大主应力和最小主应力随着注水压力的增加而减小。水力压裂的模拟结果对煤矿高瓦斯低透气性煤层的瓦斯抽采工作具有很重要的指导意义。

煤层深孔预裂爆破卸压增透效果数值模拟分析

针对高瓦斯低透气性煤层,对深孔预裂爆破进行了数值模拟分析研究。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,系统地分析了控制孔与爆破孔对于爆破卸压增透效果的影响,提出了高瓦斯低透气性煤层深孔预裂爆破的合理间距,为高瓦斯低透气性煤层的瓦斯抽采效率提出了解决方案。深孔预裂爆破为高瓦斯低透气性煤层增透、进而解决高瓦斯低透气性煤层瓦斯抽采难题提供了一条有效的途径。

低渗煤层高压水射流割缝增透技术试验研究

霍尔辛赫煤矿为高瓦斯矿井，3号煤层为较难抽放煤层，如何有效增加3号煤层透气性、提高瓦斯抽采效果，成为矿方亟需解决的问题。为此，采用自主研发的瓦斯抽采孔水力作业机，开展了低渗煤层高压水射流割缝增透抽采瓦斯技术试验研究。研究表明：经高压水射流割缝后，瓦斯抽采钻孔的平均抽采浓度增加3．87～9．31倍，平均抽采纯量增加2．67～7．33倍，增透效果显著；割缝钻孔出煤量为2．3～3．4 t，使钻孔周围煤体地应力得以有效释放，这也正是瓦斯抽采效果显著提高的主要原因。

我国低透气性本煤层增透技术现状及气爆增透防突新技术

提高煤层的透气性是高瓦斯低透气性矿井瓦斯灾害防治的根本措施。采用文献综述的方法,对我国高瓦斯低透气性本煤层采用的大孔径钻孔、密集交叉钻孔、水力冲孔、水力割缝、水力压裂、深孔爆破等主要技术的增透效果进行评述,指出了各增透方法的优劣及适用性。在充分借鉴深孔爆破和水力压裂增透技术的优点之上,提出了采用高压气体爆破致裂进行高瓦斯低透气性本煤层增透防突的新技术,即气爆增透技术;基于理论分析,揭示了气爆增透新技术的冲击震裂和尖劈压裂增透机理,指出了支撑气爆增透技术工程实践应开展的基础研究工作。

割缝排放低透气性煤层瓦斯过程的数值试验

运用岩石破裂分析系统(RFPA2D-Flow)模拟了割缝排放低透气性煤层内瓦斯的过程,验证了割缝排放煤层内瓦斯是降低低透气性煤层煤与瓦斯突出危险的有效方式。同时,数值试验对难以准确监测的煤层内瓦斯压力和瓦斯渗流场的变化规律进行了较好的模拟,为进一步理解瓦斯排放、煤与瓦斯突出机理等提供理论基础和科学依据。