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.

Study and application of the influence of inclination angle on the cross-fusion mechanism of high gas thick coal seam

In this study,to better decide the effect of coal seam dip angle upon the dynamic change of the crossfusion in gas transport and storage areas during the progress of working face in the high gas thick coal seam,a two-dimensional physical simulation experiment regarded as the theoretical research was conducted to properly explore the variation law of overburden fracture.The results demonstrated that the boundary of the gas transport zone was located in the region of fracture separation.The boundary of the gas storage area was located in the abrupt penetration zone.Also,according to the information theory,the state of the gas transport and storage areas was determined by the changing trend of the fracture rate and fracture entropy.The mathematical representation model of the dip effect in gas transport and storage areas was established.The criteria upon which the regional location of the gas transport area and gas storage area can be based were put forward.The cross-fusion evolution process of the dip effect in gas transport and storage areas was revealed as well.The research results could provide guidance for realising directional and accurate gas extraction.

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%.

Numerical calculation for gas and strata movement law caused by protection layer mining

According to the problem during mining coal seam with high gas and its control, the theory numerical calculation of gas and strata movement law caused by protection layer mining was studied, with the background of Snake Mountain coal mine. First of all, the basic principle of fluid(gas)-solid coupling was briefly described, and a three dimensional model was established by FLAC software. Secondly, the calculation parameters of fluid-solid coupling were obtained based on the measured data, and the numerical calculation of sublevel mining was carried out in turn. Lastly, initial stress state, gas movement law, deformation law of pore pressure and movement characteristics of rock strata were studied, respectively. The results show that the gas and pressure were greatly reduced with the advance of 4 coal seam working surface, as well as the constant increase of area of goaf. Facilitating gas and the stress were gradually penetrated and released to goaf during the whole process of mining. The gas pressure, the aggregation degree and the surrounding rock pressure of the 1 coal seam and the 3 coal seam were greatly reduced.

低透气性煤层长钻孔爆破增透技术

为改善高瓦斯低透气性煤层的瓦斯抽放效果,提高煤层瓦斯渗透性,以新安煤矿八号煤层为例,应用长钻孔爆破技术对煤层进行松动控制爆破,运用ANSYS/LS-DYNA软件模拟控制孔对煤岩裂隙区的影响过程。结果表明:合理布置控制孔可以增加裂隙区的范围,提高松动爆破的卸压和瓦斯排放效果。当不耦合系数为1.5、控制孔距爆破孔2 m时,裂隙区的范围约为爆破孔径的25倍。

高瓦斯松散煤体复合顶煤巷支护参数优化分析

为解决枣园煤矿23081机巷的支护难题,利用FLAC3D软件建立23081机巷模拟模型,模拟分析了巷道支护方案及参数。结果表明23081机巷顶板宜采用长2400mm锚杆,两帮宜采用长2000mm锚杆,锚杆排距600mm;采用长8300mm的锚索对顶板进行加固,锚索间距1200mm。实践表明支护系统稳定可靠,达到了预期的支护效果。

大倾角松散厚煤层高压深孔注水围岩控制技术优化实践

为提高石炭井焦煤公司4#煤层大倾角综放开采试验面松散厚煤层顶煤整体稳定性,确定了煤层注水的技术方案。通过理论分析和现场实测对注水参数和工艺进行了优化,确定了合理的湿润半径和注水压力,同时又改善了施工机具。通过现场实践,可在顶梁1.5m范围内能形成较硬的粘结层,顶煤稳定性显著提高,工作面开机率由原来的28%提高到了43%。

近距离大倾角综放工作面矿压规律及成因探析

通过对近距离大倾角综放工作面矿压实测数据的分析,获得工作面矿压显现的规律:工作面中部来压步距较小,来压强度较低,并进一步探析了内在的形成原因。由近距离大倾角工作面开采相互影响得知工作面中部和两端呈现两种不同的覆岩结构模型,中部主要承受静载荷的作用,两端承受动载荷的作用。

高瓦斯极松软煤层工作面及上风巷支护实践

芦岭煤矿针对高瓦斯极松软煤层工作面及上风巷特点,优化选择了高瓦斯极松软煤层工作面及上风巷的支护形式,保证了工作面安全生产,给相似条件下的工作面支护提供了借鉴经验。

松散煤层工作面煤壁高压注水防片帮技术研究

针对芦岭煤矿Ⅲ811松散煤层工作面煤壁片帮严重问题,采用工作面煤壁高压注水防片帮技术,综合确定Ⅲ811松散煤层工作面煤壁注水参数,包括注水孔深度10 m、注水孔间距7.5 m、注水压力7.5 MPa。结果表明,芦岭煤矿Ⅲ811工作面注水在采用上述参数40 h(5个检修班)后,两注水孔间煤体能够达到有效湿润范围,注水后减少了煤壁片帮和冒顶,现场应用效果较好。

厚煤层大采高工作面区段煤柱留设及巷道支护技术研究

针对某矿厚煤层开采时区段煤柱留设宽度较大现状,通过巷道围岩松动圈测试、理论计算的方法初步确定了煤柱宽度,由数值模拟对比了不同煤柱宽度下其塑性区及垂直应分布情况,最终确定合理煤柱尺寸。基于此提出了高预应力锚杆支护方案,有效控制了巷道围岩变形,减小煤柱尺寸并采用合理支护方案可有效增加资源回收率,提高矿井经济效益。

松软厚煤层留顶煤动压巷道围岩综合控制技术

针对松软厚煤层留顶煤动压巷道的地质特点,以阳泉某矿81206回风巷为例,在原支护参数分析与支护效果评价的基础上,对支护参数选取原则和巷道围岩控制方法进行研究。通过井下地质力学测试、围岩变形破坏特征分析,提出高预应力全断面锚索支护的综合支护技术,并开发了高强度、大面积护表构件。井下实践表明,"高预应力全断面锚索支护"综合围岩控制技术,能够解决松软厚煤层留顶煤动压巷道的支护难题,保证巷道安全。