深部孤岛工作面区段煤柱冲击地压的试验研究

以冲击启动理论为基础,结合覆岩空间结构思想,采用相似模拟试验方法,研究了孤岛工作面上覆岩层空间结构特点及采动围岩应力场的分布、变化规律,进一步探讨了孤岛工作面区段煤柱冲击地压发生机理。结果表明,两侧充分开采的孤岛工作面上覆岩层呈"C"型覆岩空间结构,工作面承受上部岩层及两侧采空区上覆岩层转移过来的部分岩层重量,在工作面两侧形成应力集中区域,导致采动围岩应力场达到极限平衡状态,该集中应力可视为采动围岩近场极限平衡系统的静载荷。孤岛工作面开采过程中"C"型覆岩空间结构逐渐演化形成"W"型空间结构,极限平衡系统静载荷发生转移和改变,最终由上下区段煤柱全部承担上覆岩层重量,系统载荷增至最大,处于临界失稳状态。"W"型覆岩空间结构大面积失稳,为系统提供了外动载荷,系统在动载荷的扰动下突破平衡极限,从而发生区段煤柱冲击。最后,基于孤岛工作面应力分布规律确定了区段煤柱的合理尺寸。

Experimental study on the rockburst of the coal pillar in the deep isolated workface

The paper is inclined to present its experimental study on the rockburst of the coal pillar section in the deep isolated workface in coal mining practice based on the rookburst initiating theory and the idea of overlaying strata of the spatial structure.For the study purpose,we have made a dynamic simulation test method by studying the spatial structure characteristic features of the overlaying strata and the distributive rule of the surrounding rook stress in the isolated mining workface so as to be able to monitor the coal stress in the process of mining by using a BW-0.5 micro-stress detector and a YJZ-2 intelligent digital strain testing system.In proceeding with our study,we have made an examination of the rockburst mechanism of the coal pillar section in such workface ulteriorly from a distance far away through analyzing the spatial and temporal evolutionary regularity of the surrounding rock stress.The results of our experimental studies show that,the spatial structure of the overlaying strata tends to be in a letter "C" form when both of the isolated workface sides have been almost wholly mined out and resulted in a goaf,which has to be supported and propped merely by the weight of the upper strata and some of the metastasized overburdened rock of the goaf.In such a case,it seems to be natural for the stress field of the surrounding rocks to be fooused on the two sides of the workface.What is more,the space structure in the letter "C" form may gradually evolve into a letter "W" one in the process of mining.Thus,the said isolated section and the limit equilibrium system of the static load shift would gradually turn to be a section of the coal pillar and take over all the weight of the overburdened rock.It is in this manner that the static load shift may increase to the maximum limit,with the system turning to be in a critical state of instability.Furthermore,the obvious instability of "W" space structure would lead to the transfer of the original static balance and the breakdown of the original balanced limit,thus leading to the rockburst of the coal pillar.Besides,we have also made an analysis of the size of the coal pillar section based on the isolated face stress distribution regularity,arriving at a conclusion that the reasonable size of the section coal pillar should be made between 0-5.0 m,which can help to eliminate the likely rockburst risk effectively.