矿震扰动下采区煤柱应力偏量集中区诱冲机制及防治方法

The mechanism of rockburst in district coal pillar with high deviatoric stress and mining tremors impact and its prevention methods

以张双楼矿西一采区生产地质条件为工程背景,基于应力偏量、等效应力、Mises强度准则、能量释放速率分析了煤岩冲击失稳的充要判别准则,揭示了采区煤柱覆岩结构、应力偏量、矿震事件随工作面回采演化规律,并探讨了矿震扰动下采区煤柱冲击危险防治方法.结果表明:煤岩冲击失稳充要条件为开采活动及矿震扰动引起的应力偏量超过煤岩体强度极限,且单位时间内煤岩系统释放弹性能量与矿震应力波输入能量之和大于煤岩系统稳态破坏消耗能量;随着采区工作面持续开采,采区煤柱两侧覆岩形成"T"型悬臂结构并不断损伤破坏;以标量应力偏量第二不变量J2表征应力偏量σ′_(ij),煤柱区应力偏量前期呈"M"型分布并逐渐向单峰型转变,屈服破坏区逐渐向煤柱中部扩展;以矿震频次、能量、震源位置表征应力波扰动σ_(ij)~d,矿震扰动以低能量事件为主,且主要集中于正回采工作面及采区煤柱区域.根据分析结果,提出矿震扰动下采区煤柱切顶爆破、扩大采区煤柱宽度、跨上山开采、大直径钻孔卸压等防冲方法.

The mechanism of rockburst during mining was analyzed on the base of deviatoric stress, equivalent stress, Mises criterion and energy balance theory. Additionally, the overly- ing strata movement, deviatorie stress and mining induced tremor activity in relate to active mining, as well as the rockburst prevention methods, were studied with the geological condi- tion of Zhangshuanglou coal mine. The results show that two criteria should be satisfied for causing rockburst, firstly the overlap deviatorie stress caused by gob and tremors surpasses the strength of coal, secondly the overall energy release ratio of elastic energy cumulated in coal and dynamic energy induced by tremors surpasses the energy consume ratio of steady fractu- ring. As the excavation processing, the overlying strata would break and form T-shape struc- ture around the district coal pillar. Taking the second invariant of deviatoric stress （J2） to re- ! I present the deviatoric stress （ali）, it is noticed that a0 has a M-shape over the coal pillar and transfers to n-shape as the mining processing, which means the plastic fracture zone is exten- ding to inner pillar zone. The dynamic stress was analyzed in terms of seism frequency, energy and seismic focus, it is found that the majority of tremors have low energy and their focus gath- ered in mining zone and district coal pillar zone. Accordingly, several methods are proposed to prevent rockburst, such as overlying strata bursting, extending the width of coal pillar, over- lying strata mining and large stress-relief borehole.