构造异常区能量单元切割理论及冲孔–爆破协同增透技术

Study and application of the energy unit cutting theory and punching-blasting synergy permeability enhancement technology in tectonic anomaly areas of coal mines

  • 摘要: 煤矿构造异常区通常具有应力集中、高瓦斯赋存、低渗透性、构造煤发育及致灾能量分布不均匀的特点,是煤与瓦斯突出重点防控区域。水力/气动冲孔技术是构造煤卸荷瓦斯抽采的主要手段之一,相较于常规抽采钻孔,可明显提高卸压半径,但煤层相邻冲孔钻孔之间易形成新的应力集中带,限制和影响瓦斯抽采。采用理论分析,数值模拟和现场实验相结合的方法,研究了冲孔与爆破联合卸压增透降能消突原理。主要研究结论为:① 提出了突出能量单元切割理论及冲爆协同增透技术,结合突出潜能分布和突出启动能量判据,将煤层划分若干个能量单元,进行边界处切割、内部分区治理。针对构造异常区煤体采用先冲孔后可控定向聚能爆破的方式对煤体定向致裂、释放应力,冲孔孔洞为爆破影响范围内煤体移动提供了自由空间,在爆破点处形成了煤体自由面并改变了煤层的连续性,爆生气体与定向应力波可促进应力再平衡。② FALC3D模拟显示,冲孔可以降低孔周煤体应力,随着冲孔半径的增大,卸压半径亦随之增大。且冲孔后会在孔周卸压区外形成一定范围的应力集中带,限制瓦斯流动。③ 阐明了可控定向聚能爆破技术的介质–能量切割原理,爆破改变了被切割单元煤体自由面附近的突出潜能赋存梯度,实现介质切割控制能量切割。单元切割有效增加了采掘工作面前方阻能区长度,降低了低能–高能过渡带内作业风险。④ 利用ANSYS/LS–DYNA软件,模拟了煤层可控定向聚能爆破与冲孔孔洞协同作用,结果表明可控定向聚能爆破实现了对煤体的定向致裂,在聚能方向上侵彻煤体形成较大裂隙。随着时间推移,以冲孔孔洞作为控制孔的孔周产生环向裂隙网,并随着裂隙扩展逐渐与非聚能方向的裂隙贯通,实现对煤体的有效增透。⑤ 冲爆协同增透技术现场试验表明,爆破孔周围10 m范围内冲孔区域煤体应力和排渣量显著降低,单、双根聚能管爆破后的瓦斯抽采纯量分别提高1.76 ~ 4.35倍和1.35 ~ 8.60倍。水力冲孔瓦斯有效抽采半径仅为5 m,冲孔与爆破协同卸压增透影响半径大于10 m,卸压效果提高一倍以上,煤巷月掘进速度提高了20 m。

     

    Abstract: The coal seams in tectonic anomaly areas have high gas content, high geostress, low permeability, the development of tectonic coal, and uneven distribution of disaster-causing energy. These areas are key for preventing and controlling coal and gas outburst accidents. Hydraulic/pneumatic punching technology is one of the main methods for gas drainage in tectonic coal. Compared to conventional drilling for gas extraction, it significantly increases the pressure relief radius. However, new stress concentration areas easily form between adjacent punching holes in the coal seam, limiting and affecting gas extraction. This paper combined theoretical analysis, numerical simulation, and field experiments, this study investigated the principles of energy reduction and outburst prevention using combined punching and controlled energy-accumulating blasting measures. The main conclusions of this paper are as follows: ① This paper proposes an Outburst Energy Unit Cutting theory and a punching-blasting synergistic permeability enhancement technology, combining with the distribution of outburst potential and outburst start-up energy criteria, dividing the coal seam into several energy units, and carrying out cutting at the boundary and internal zoning management. Essentially, this method involves punching holes first, followed by controlled energy-accumulating blasting to create directional fractures in the tectonic areas of the coal seam, releasing stress. The punched holes provide free space for the movement of coal within the impact range of the blasting injection, forming a free surface of the coal at the blasting injection point and altering the continuity of the coal seam. The generated explosive gases and directional stress waves can promote stress rebalancing. This alters the gradient of elastic and gas expansion energy in the coal body, effectively cutting the energy units in tectonic anomaly areas. ② The FALC3D numerical simulation shows that punching can reduce the stress in the coal around the hole. As the punching radius increases, the pressure relief radius also increases. After punching, a certain range of stress concentration forms outside the pressure relief zone around the hole, which limits gas flow. ③ The media-energy cutting principle of controlled directional cumulative blasting technology is clarified. The blasting changes the outburst potential occurrence gradient near the free surface of the coal of the cutting unit, realizing the media-cutting-controlled energy cutting. The unit cutting effectively increases the length of the energy-resistant zone in front of the mining work and reduces the risk of operation in the low-high energy transition zone. ④ A numerical model was constructed based on the fluid-solid coupling algorithm to simulate the synergistic effect of controlled directional energy-focused blasting and punching holes. Results indicate that controlled energy-accumulating blasting achieves directional fracturing of the coal seam, forming larger cracks in the energy concentration direction. Over time, radial crack networks form around the punched holes as the control hole, eventually connecting with cracks in non-energy concentration directions, effectively enhancing permeability in tectonic anomaly areas. ⑤ Field tests show that within a 10-meter range around the blasting hole, the stress and debris amount in the punched area of the coal body significantly decreases. The gas extraction volume after using single and double energy-focused tubes was 1.76 to 4.35 times and 1.35 to 8.60 times, respectively, compared to before blasting. The effective gas extraction radius of hydraulic punching was only 5 meters, while the synergistic pressure relief and permeability enhancement radius of punching and blasting were at least 10 meters, more than doubling the pressure relief radius in tectonic anomaly areas, and the monthly driving speed of coal roadway has been increased by about 20 m per month.

     

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