特厚煤层沿空掘巷力源结构特征与围岩协同控制策略

Characteristics of stress sources and comprehensive control strategies for surrounding rocks of gob-side driving entry in extra thick coal seam

14~20 m特厚煤层小煤柱沿空掘巷围岩控制是当前煤矿巷道支护领域的难题之一.以山煤国际晋北矿区典型的19 m特厚煤层孤岛综放面小煤柱沿空掘巷工程为研究对象,分析了特厚煤层覆岩应力拱、断裂拱大结构特征以及基本顶侧向破断运动规律,建立了特厚煤层沿空掘巷“双力源”结构模型,揭示了“双力源”传递作用机理及其对沿空掘巷围岩稳定性的影响规律,提出了“远场弱化-近场强化”协同控制治理策略,开展了19 m特厚煤层8 m小煤柱沿空掘巷围岩控制现场试验.结果表明:特厚煤层沿空掘巷强矿压显现源于小煤柱侧Ⅰ型力源和实体煤侧Ⅱ型力源叠加作用;采用小煤柱侧(Ⅰ型)和实体煤侧(Ⅱ型)力源结构“水力压裂+深孔爆破”复合弱化后,基本顶周期来压步距降低了约69.6%,有效阻断了采动应力向围岩传递;通过“远场弱化-近场强化”协同控制技术,有效控制了特厚煤层沿空掘巷掘进与回采期间围岩稳定.研究成果为14~20 m特厚煤层小煤柱工作面安全高效开采提供了一定的理论依据与技术支撑.

The control technology for surrounding rocks of gob-side driving entry in 14—20 m coal seams is one of the challenges in the field of roadway support.A gob-side entry driving with small pillar in fully mechanized caving face around goaf of 19 m coal seam in Shanxi Coal International Energy Group Co.,Ltd.,was selected as the research object.The structural characteristics of stress arch and fracture arch of the overlying rocks,as well as the lateral fracture movement characteristics of the main roof were analyzed.A dual-stress-source model for the gob-side entry driving of the thick coal seam was proposed to reveal the transmission mechanism of the stress sources and its impact on the stability of the surrounding rocks.Moreover,a comprehensive control strategy of far-field-weakening and near-field-strengthening was proposed.An industrial test of the surrounding rock control for the gob-side entry driving with 8 m coal pillar in 19 m extra thick coal seam was conducted on site.The results show that the strong stress of the gob-side entry driving is caused by the superposition of modeⅠstress source from the small coal pillar side and modeⅡstress source from the entity coal side.The pressure step distance of the main roof is reduced by about 69.6%after implementing the weakening technology of hydraulic fracturing and deep blasting at the small coal pillar side(modeⅠ)and entity coal side(modeⅡ),effectively blocking the transmission of mining stress to the surrounding rock.Meanwhile,combined with the strengthening support technology,the stability of the gob-side entry driving is effectively controlled.The research results have theoretical and engineering guidance significance for safe,efficient,and high recovery mining of 14—20 m thick coal seams.