逆冲断层卸载失稳机理研究

Mechanism of thrust fault rupture causing by unloading effect

  • 摘要: 逆冲断层失稳诱发的冲击地压严重威胁着煤矿的安全,但目前采动条件下逆冲断层的失稳机理仍不清楚,使得断层冲击地压防治工作缺乏科学指导。 为探索逆冲断层卸载失稳机理,基于典型逆冲断层控制型矿区的工程地质概况,分析了逆冲断层冲击地压的显现特征;采用相似模拟和数值模拟手段,研究了开采扰动引起的逆冲断层卸荷效应,阐明了义马矿区逆冲断层卸载失稳的模式及过程;通过实验室实验方法,揭示了单侧卸载过程中逆冲断层失稳瞬态的位移场时空演化规律,建立了断层卸载失稳的力学模型,阐释了断层失稳瞬间的黏滑过程。 研究结果表明:随着开采范围与F16断层距离的减小,断层冲击地压危险性显著增大,冲击地压所释放能量急剧增高;采动引起逆冲断层产生卸荷效应,即开采扰动使得断层带新裂纹萌生并局部离层,断层带上交错出现应力集中区和应力减弱区,断层上段出现逆时针滑移,而下段顺时针滑移;卸荷效应导致断层失稳的过程可分为线性稳态(I)、非线性稳态(II)、亚失稳(III)和失稳(IV)4个阶段;断层卸载失稳瞬间正应变和剪应变总体上呈突降-突增-降低至稳定的变化趋势,且相对于中部和下部,断层上部滑移位移受卸载扰动影响较大;断层卸载失稳瞬间的能量传递过程为:震源单元-围岩杆单元-相邻围岩杆单元-相邻断层带单元等,其黏滑失稳是一系列单元连锁失稳构成的综合结果。 通过本文研究,对逆冲断层卸载失稳的机理形成了新的认识,包括卸载失稳模式、失稳过程、失稳瞬态的能量传递等。

     

    Abstract: Rock burst caused by thrust fault instability,as one of the most common disasters,threatens the safety of coal mines. But it is still unclear on the effect of thrust fault slipping to rock burst,making the prevention of rock burst very difficult. To explore the mechanism of thrust fault rock burst under unloading condition,the features of bursting were analyzed on the basis of engineering and geological conditions of Yima mine. Combining the similar simulation experiment and numerical simulation test, the unloading effect caused by mining disturbance and the fault rupture process were studied. Then the spatiotemporal evolution of displacement field when fault slipped was revealed on the basis of laboratory experiment,afterwards the mechanical model presenting the fault slides was proposed with the stick- slip process. The research results are as follows: ① with the decrease of the distance between the mining area and F16 fault,the risk and released energy of rock burst increase rapidly. ② Mining can cause unloading effect,which is mining disturbance inducing new cracks and partly abscission in the fault,stress concentration and reduction appearance alter- nately in the fault zone,upper part slides counterclockwise and lower part slides counterclockwise. There are four pha- ses,which are linear(I),nonlinear(II),sub-instability(III) and instability (IV) when fault ruptures. ③ The transient normal and shear strain of fault dislocation mainly presents a trend which is sudden drop-sudden increasing-decrea- sing-stability,while the upper part is more unstable than the lower part when the fault slips. Fault rupture is a chain re- action which includes the failures of hypocenter element,surrounding rock bar element,adjacent rock bar element and adjacent fault zone element and so on. New understanding such as the patterns of fault slip under unloading,rupture process and energy transporting etc. ,were described in this paper.

     

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