强突煤层群非连续开采应力叠加特征与瓦斯分区精准防治

Precise zoning control of coal seam gas in discontinuous mining face of strong outburst coal seams group

  • 摘要: 随着浅部煤层及易开采煤层资源的日渐枯竭,许多老旧矿井由于煤层复杂瓦斯赋存情况及前期不合理的采掘规划,后续开采的邻近层工作面受应力叠加影响,瓦斯治理困难。以芦岭煤矿Ⅱ944工作面为研究对象,利用数值模拟方法分析了上下突出邻近层非连续回采后遗留煤柱形成的工作面叠加应力分布状态,通过理论分析获得应力集中区渗透率分布特征,基于此提出了“灾害分区,精准防治”关键技术。研究结果表明:Ⅱ944工作面应力分布呈现非连续时空分区分布状态,上下邻近层先后回采留设煤柱的时空顺序发生变化时,会导致中间煤层的低应力集中区转变为强显现的应力集中区、卸压区转变为应力集中区,因此,可将这些区域划分为卸压区、局部卸压区和应力集中区。应力集中区的最大垂直应力达到102 MPa,渗透率大幅降低。瓦斯治理前最大煤层瓦斯压力3 MPa、最大瓦斯含量16.72 m3/t。依据应力分布、渗透率及瓦斯赋存特征,制定了针对性的分区精准瓦斯治理技术,形成保护层卸压−水力造穴−网格式预抽协同治理的工作面瓦斯精准治理模式;局部卸压区域通过网格式穿层钻孔预抽后瓦斯压力降低至0.18 MPa,瓦斯含量降低至2.45 m3/t。应力集中区域通过水力造穴及网格式穿层钻孔预抽后瓦斯压力降低至0.15 MPa,瓦斯含量降低至2.50 m3/t。整个回采期间未发生瓦斯超限事故,实现了非连续开采诱致叠加应力分布下的安全高效开采。上述研究对指导突出煤层群复杂工程条件的瓦斯精准治理工作具有重要意义。

     

    Abstract: As shallow coal seams and easily exploitable coal resources gradually deplete, many old mines face challenges in gas management due to the complex gas occurrence in coal seams and irrational mining plans in the early stages. This results in stress accumulation affecting adjacent working faces during subsequent mining operations. Taking the Lu Ling Coal Mine Ⅱ944 working face as a case study, the author used numerical simulation methods to analyze the stress distribution caused by the residual coal pillars formed after discontinuous mining of upper and lower protruding adjacent layers. The study also obtained the permeability distribution characteristics in stress concentration zones through theoretical analysis, proposing the key technology of “disaster zoning for precise prevention”. The research reveals that the stress distribution of the Ⅱ944 working face shows a non-continuous spatiotemporal zoning pattern. When the temporal sequence of mining and leaving coal pillars in the upper and lower adjacent layers changes, the low-stress concentration zone in the middle coal layer can transform into a prominently stressed concentration zone, and the depressurized zone can transform into a stress concentration zone. These zones can be categorized as depressurized zones, local depressurized zones, and stress concentration zones. The maximum vertical stress in the stress concentration zone reaches 102 MPa, with a significant decrease in permeability. Prior to gas management, the maximum coal seam gas pressure was 3 MPa, and the maximum gas content was 16.72 m3/t. Based on stress distribution, permeability, and gas occurrence characteristics, targeted zoning and precise gas management technologies were developed. This resulted in a working face gas precise management model, involving protective layer depressurization, hydraulic flushing, and grid-pattern pre-drainage. In the locally depressurized zone, gas pressure was reduced to 0.18 MPa, and gas content decreased to 2.45 m3/t after pre-drainage through grid-pattern cross-layer drilling. In the stress concentration zone, gas pressure was reduced to 0.15 MPa, and gas content decreased to 2.50 m3/t through hydraulic flushing and grid-pattern cross-layer drilling. No gas exceedance accidents occurred throughout the entire mining period, achieving safe and efficient mining under the stress distribution induced by non-continuous mining. This research holds significant importance in guiding precise gas management in challenging engineering conditions of protruding coal seam groups.

     

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