厚煤硬顶条件下综放末采回采效率提高对策研究

Enhancing recovery efficiency during the final mining phase of fully mechanized caving mining under thickcoal hardroof conditions:countermeasures and strategies

针对厚煤硬顶工作面末采期间存在大面积悬顶引起的采动应力集中及回采效率低的问题,以唐家会煤矿61304工作面为工程背景,运用相似模拟试验、理论分析、数值模拟和现场实测等综合研究方法,在分析16.8 m特厚煤层以及15.8 m厚硬基本顶工作面末采期间覆岩垮落规律、悬臂结构力学传递机制、应力演化特征等影响因素的基础上,采用爆破切顶协同控制顶板技术,以达到提高回采率的目的。结果表明:覆岩悬臂结构在回采时期产生超前应力集中,导致末采期间顶煤回收量降低,停采煤柱被迫增加;爆破切顶破坏末采时期悬臂结构,切断超前采动应力传播途径,厚硬基本顶对工作面传递压力减弱,工作面放顶距离延长;悬臂角度与超前应力峰值呈负相关,悬臂长度与超前应力峰值呈正相关,通过破坏悬臂结构缩短悬臂长度可降低超前应力峰值;末采期间爆破切顶后超前应力峰值平均降低约5.76 MPa,停采煤柱缩短20 m,煤炭回收效率提高。工程实践表明,爆破切顶工艺能改善末采时期顶板悬空引起的采动应力集中,有效控制平巷围岩变形,极大提高煤炭回收效率,保障末采期间安全高效回采。

To address the challenges of high mining stress concentration and low mining efficiency caused by largearea suspended roofs during the final mining phase of thick coal hardroof working faces,comprehensive research methods including similar simulation tests,theoretical analysis,numerical simulations,and insitu experiments were employed.The study set the 61304 working face of Tangjiahui Coal Mine as an engineering background and focused on the final mining phase of the 16.8 m extrathick coal seam overlaid by 15.8 m thick hard main roof,taking into account factors such as the collapse pattern of overlying rock,mechanical transfer mechanism of the cantilever structure,characteristics of stress evolution,and other influential factors.In response,a roof collaborative control technology characterized by blasting roofcutting was proposed to enhance the recovery rate.The findings of this study revealed that the cantilever structure of overlying rock caused stress concentration during the mining process,resulting in reduced top coal recovery during the final mining phase and necessitating the increase of stopping-protection coal pillars.By employing blasting roof-cutting,the cantilever structure was destroyed during the final mining phase,thereby reducing the stress transmission path of abutment mining-induced stress and weakening the transmission stress originating from the thick and hard main roof above the working face.Consequently,the caving distance of the working face could be extended.It was observed that the cantilever angle exhibited a negative correlation with the peak abutment stress,while the cantilever length showed a positive correlation.Shortening the cantilever length through the destruction of the cantilever structure helped reduce the peak stress.The average peak abutment stress was reduced by approximately 5.76 MPa through blasting roof-cutting during the final mining phase,leading to a 20-meter reduction in the width of the stopping-protection coal pillar and an improved coal recovery efficiency.Engineering practice demonstrated that blasting roof-cutting could mitigate mining-induced stress concentration resulting from roof suspension during the final mining phase and effectively control the deformation of surrounding rock in the entry.This significantly improved the coal recovery rate while ensuring safety and efficiency during the final mining phase.