复杂坚硬岩层条件下特厚煤层综放开采矿压分级预测

Prediction on weighting classification of fully-mechanized caving mining under extremely thick coal seam

顶板事故发生起数和死亡人数长期以来在我国煤矿各类事故中占有很大比例,特别是覆岩存在多层坚硬岩层时,其覆岩结构具有系统性、复杂性,易造成强烈的矿山压力显现,甚至诱发矿井动力灾害。因此,亟需提出适用于复杂坚硬岩层条件下矿压分级预测方法,为坚硬岩层控制提供理论支撑。基于复杂坚硬岩层条件下特厚煤层综放开采矿压显现特征,确定了不同空间位置坚硬岩层具有不同的矿压控制作用,即低位坚硬岩层控制小周期来压、中位坚硬岩层控制大周期来压、高位坚硬岩层控制强矿压显现;基于板壳力学、塑性力学理论,结合不同空间位置坚硬岩层的控制作用,建立了坚硬岩层“多层位板式结构”系统模型,根据结构形式将坚硬岩层划分为近场悬臂结构和远场砌体结构,揭示了复杂坚硬岩层破断运动过程具有渐进、复合等特征;建立了一套坚硬岩层破断尺度判据,形成了复杂坚硬岩层条件下的矿压分级预测方法。以大同矿区石炭系特厚煤层综放开采矿井为工程背景开展了矿压分级理论预测,通过分析现场矿压监测、微震监测数据,证实了复杂坚硬岩层条件下的矿压分级预测方法的适用性。研究成果一定程度上实现了复杂坚硬岩层的可知、可控,但不同坚硬岩层控制的结构破断时能量是如何传递至采场范围并引起动力显现的机理尚未完全阐明,该问题的研究可为坚硬岩层的精准控制提供理论支撑。

The numbers of roof accidents and deaths have long occupied an important position in various types of coal mine accidents in China,especially when there are multiple hard stratum in overburden.The structures of multiple hard stratum are systematic and complex,which can easily causes strong strata behavior,even induces dynamic disasters.Therefore,there is an urgent need to develop a method for predicting weighting classification under complex hard rock formations in order to provide a theoretical support for the control of hard rock formations.In this paper,based on the characteristics of fully mechanized top coal caving mining under the conditions of complex hard rock layers,it is determined that the hard rock layers in different spatial positions have different pressure control effects.That is,the low-level hard rock layer controls small-period weighting,the medium-level hard rock layer controls large-period weighting,and the high-level hard rock layer controls strong strata behavior.Based on the theory of plate and shell mechanics and plastic mechanics,a“multi-layer slab structure”system model of hard rock layers was established,and the hard rock layers were divided into near-field cantilever structures and far-field masonry structures,according to the structural form.It reveals that the process of breaking motion of complex hard rock layer has the characteristics of gradual and compound.The criterion of breaking scale of hard rock layer is established,and the method of grading prediction of rock pressure under the condition of complex hard rock layer is formed.Based on the engineering background of fully mechanized top coal caving mining in the Carboniferous ultra-thick coal seam of Datong mining area,the theoretical prediction of weighting classification was carried out.The applicability of the rock pressure classification prediction method under complex hard rock formation conditions was verified by analyzing on-site rock pressure monitoring and micro-seismic monitoring data.The research results have achieved a certain degree of knowability and controllability of complex hard rock formations.However,the mechanism of how energy is transferred to the working face causing dynamic appearance is not fully understood when the structure controlled by different hard rock formations is broken.The study of this problem provides a theoretical support for the precise control of hard rock formations.