柱式采空区蹬空复采充填体高-强协调机制及其临界高度研究

Height-strength coordination mechanism of filling body in pillar goaf and its critical height in kick-off mining

柱式采空区上层遗煤蹬空安全复采的关键在于确保底板煤岩柱的采动稳定性。针对山西朔州中煤金海洋煤业公司6#煤层蹬空开采底板煤柱易失稳诱发上行工作面垮塌的现象,提出地面注浆充填加固底板煤柱工程技术,借助于注浆充填固结体对底板煤柱形成的夹持作用,抑制底板煤柱采动裂缝扩展并提升其承载能力。综合采用数值模拟、理论分析和现场实测,研究不同强度及高度充填固结体夹持作用下底板煤柱采动裂缝及极限承载能力演化规律,并以裂缝数量和峰值强度为指标,定量表征不同强度和高度充填体对底板煤柱采动裂隙扩展的抑制效应和承载能力的强化效应,研究揭示不同充填体高度和强度的"高-强"协同作用及其底板煤柱增稳机制,据此确定柱式采空区注浆充填材料合理强度的配比方案及注浆充填体临界高度,即粉煤灰水泥比为2∶1的混合浆液、固结强度为4 MPa和高度至少为6 m的充填体。论文研究阐明了充填体强度和高度对底板煤柱的耦合增稳机制,可为蹬空安全复采下伏采空区注浆加固提供有益指导,对优质遗煤资源安全复采具有重要意义。

The key to safe re-mining of upper layer coal seam of pillar goaf is to ensure stability of floor coal pillar. In view of floor coal pillars in coal seam 6 of Gold Ocean Coal Company of China Coal Group in Shuozhou, Shanxi prone to lose stability and cause collapse of upper working face, the engineering technology of grouting to strengthen floor coal pillars was proposed. The clamping effect of filling body on floor coal pillars inhibits the expansion of mining fractures of floor coal pillars and enhances its bearing capacity. Evolution law of both mining fractures and maximum bearing capacity of floor coal pillars under the influence of clamping effect of filling bodies with different intensities and heights were studied through numerical simulation, theoretical analysis and field measurement.Moreover, the number of fractures and its peak strength were taken as references, and inhibiting effect of filling bodies with different strength and heights on fracture expansion and its strengthening effect on bearing capacity were quantitatively manifested. The study has revealed the "height-strength" synergy of different filling heights and strengths and its stabilization mechanism for the floor coal pillars. Based on this, reasonable ratio plan of the grouting materials for filling pillar goaf and critical height of filling body are determined: a mixed slurry with a fly ash cement ratio of 2∶1, filling body with a concretion strength of 4 MPa and a height of 6 m. The research results clarify coupling stabilization mechanism of strength and height of filling body, which provides useful guidance for grouting and reinforcement of underlying goaf and is of great significance to safe re-mining of high-quality coal resources.