急斜煤层采空区顶板弱化方案优化及效果评价

Scheme optimization and its effect evaluation of void roof weakening in mining steeply inclined coal seams

急倾斜煤层采空区顶板易出现大范围悬顶及突发性垮落,诱发动力灾害,现场采用电磁辐射仪与微震监测,评价原有采空区顶板弱化方案实施效果,并探究水力致裂与切顶爆破耦合弱化方案的可行性,优化弱化方案的工序及参数,分析优化方案实施效果及经济效益。研究表明:原有方案中电磁辐射最大值已超过100 mV,煤岩破碎程度较低;耦合弱化方案简化施工流程,电磁辐射平均幅值仅为17.0 mV,耦合弱化方案显著削弱了顶板应力集中;改变了顶板能量存储释放方式,煤岩微震事件数以Ⅲ,Ⅳ级别事件为主,降低了发生动力性灾害的几率。优化方案实施后,工作面平均月推进量较以往增幅84%,平均单月产量增幅131.2%,工作面平均回采率提升至48.82%,最大单日回采率83.59%,百米实施成本仅为原方案成本的58.96%.研究成果为乌东煤矿动力灾害防控提供重要理论依据。

The void roofs are easy to be hanged in a large scale and collapse suddenly after top-coal caving inducing relevant dynamic hazards.Hybrid monitoring including electromagnetic radiation and microseism is offered for assessing implementation effect of original scheme of void roof weakening in the site.Moreover,Feasibility of coupling weakening combining both hydraulic fracturing and cutting blasting is analyzed.The relative procedures and parameters for the coupling weakening have been determined and the implementation and economical benefits were totally compared with the original scheme.The relevant results indicate that maximum of the electromagnetic radiation exceeds 100 mV in the original scheme and degree of coal-rock mass fragmentation is low.Contrary,the coupling scheme not only simplifies the implementation process,but also weaken stress concentration with average value of the electromagnetic radiation 17.0 mV.Simultaneously,the new scheme alters energy storage-release mode of the void roof availably.The microseism events are mainly focused onⅢandⅣlevel and probability of the dynamic hazards is also reduced.After the coupling scheme implementation,average monthly advance mount increased by 84%than the original data.Average monthly output growth is 131.2%.Average recovery rate and Maximum one-day recovery rate both increase to 48.82%and 83.59%.Besides,implementation cost per 100 meters is only 58.96%of the original cost.All research results would provide important theoretical basis for dynamic hazard prevention and control in Wudong coal mine.