临断层孤岛面冲击危险与断层滑移数值反演——以朝阳煤矿3108工作面为例

Back analysis of rock burst risk and fault slip due to mining in the island panel along fault:A case study of island panel 3108 in Chaoyang Coal Mine

复杂地质构造、开采布局等与冲击地压密切相关,尤其是当孤岛工作面沿平行于断层走向回采时,受断层煤柱与孤岛工作面影响叠加后形成的采场煤岩应力状态及覆岩结构将更为复杂,严重威胁冲击地压矿井的安全高效开采。为探究临近断层处孤岛工作面开采时断层滑移失稳致灾机理,利用FLAC3D中的Fish语言进行2次开发,系统地提出一种孤岛工作面推进过程中采动诱发断层滑移失稳的数值模拟方法。以朝阳煤矿3108工作面为工程背景,建立断层赋存条件下的孤岛工作面开采的数值模型,分析了开采扰动下断层面应力场、位移场和速度场的动态演化特征,确定了断层滑移失稳的判定准则,总结了断层滑移失稳与冲击危险之间的关系,所得结果与现场实际强矿震分布具有较好的一致性。研究结果表明:当工作面远离断层时,断层面不产生滑移失稳,此时采动动载主要源于顶板破断;当工作面向断层推进时,认为当断层面出现剪应力降且剪切位移量大于0.05 m时断层产生滑移。断层滑移型动载可由地震矩、能量和滑移速率等物理参数表示,当动力计算时间为0.03 s时,断层面发生滑移,其地震矩和释放的能量达到峰值。一般当滑移速率峰值达到0.99 m/s以上时可认为断层滑移反作用于采场周围煤岩体的影响较大,断层滑移速率随时间变化先增大后减小,一般在动力计算0.4~0.5 s时,滑移速率达到峰值,当断层滑移结束后,滑移速率会降低至某一值。在整个孤岛工作面的回采进程中,断层滑移速率首先呈现阶梯式跃增趋势,后期表现为线性增长,即断层滑移最易出现在工作面初次来压和见方阶段,易于诱发强矿震和冲击地压。

The relationship between complex geological structure,mining layout and rock burst is a major concern in coal mining.Especially when the island panel mining along the strike direction of fault,the stress state and overlying strata structure induced by the superposition of fault pillar and island panel will be more complex,pose a serious threat to the production and safety of rock burst coal mines.To study rock burst disaster induced by fault slip,the numerical algorithm of FLAC3 D is developed by using Fish language,a systematic approach to numerically simulate an island longwall panel operation is proposed to investigate the dynamic response of fault slip instability.Based on the engineering background of the island panel 3108 in Chaoyang coal mine,a numerical model of island panel mining with fault structure is constructed,the dynamic evolution characteristics of stress,displacement and velocity under mining disturbance are analyzed,the criterion of fault slip instability is determined,the relationship between fault slip instability and rock burst risk is summarized,and the result matches the field observations of strong tremor distribution.The results show that as the mining panel is far from the fault,the fault slip does not occur.At this time,the dynamic load mainly comes from roof fracturing.When mining activities approach the fault,the calculation of the dynamic response of fault slip is performed over the area where the increase of relative shear displacement during dynamic analysis exceeds 0.05 m and where the shear stress along the fault decreases.Dynamic load induced by fault slip can be expressed by seismic moment,energy and slip rate,etc.Dynamic load induced by fault slip can be expressed by seismic moment,energy and slip rate,etc.Numerical results show that when dynamic time is 0.03 s,fault slip occurs,the seismic moment and the released energy reach a peak value.It is generally accepted that as the particle velocity reaches 0.99 m/s,severe damage will be induced in the surrounding rock by fault slip.The slip rate increases and reaches a peak value at a dynamic time of about 0.4 to 0.5 s and subsequently decreases sharply.It is shown that during the initial stage of the mining process,and in a square mining panel,fault slip is more likely to occur,leading to strong tremors and rock bursts,which become more notable in the later stages of the mining of the island panel.