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阶梯状断层上盘工作面回采期间应力演化规律研究

Study on stress evolution law during coal winning of hanging wall working face of step fault

  • 摘要: 工作面开采至复杂地质区域时随构造应力变化而形成应力增高区,煤岩体内易积聚大的弹性应变能,其应力场、能量场分布及动态演化对井下冲击地压等动力现象有显著诱导影响。利用UDEC数值模拟软件,研究工作面上盘开采过阶梯状断层(组合正断层)时超前支承应力的分布及演化规律,并结合能量分布、断层活化对阶梯状断层上盘工作面回采期间冲击危险区域及等级进行综合判识。结果表明:工作面向断层开采时具有应力阻隔效应,在开采盘出现应力集中现象,阻隔效应加剧了弹性应变能积聚,是诱导工作面冲击地压发生的重要因素;在过首条断层后向下一条断层开采期间,工作面超前支承应力相对较小,但两断层间顶板区域能量增高,存在潜在冲击危险;工作面向阶梯状断层推进时,工作面前方近断层顶板沉降变形易引起断层活化,当工作面与断层距离小于20 m时,阶梯状断层活化明显。研究结果可为相似阶梯状断层条件下冲击地压预测及危险区域划分、工作面布置、开采顺序选取等提供参考。

     

    Abstract: When the working face is mined under complex geological areas, the stress-concentrated area is formed with the change of tectonic stress, and a large amount of elastic strain energy is easily accumulated in the coal rock. The distribution and dynamic evolution of stress field and energy field have a significant induction effect on the dynamic phenomena such as underground rock burst. In this study, the UDEC numerical simulation software was used to study the distribution and evolution law of the advanced support stress when the working face was mined over the step fault (combined normal fault). Combined with the energy distribution and fault activation, the dangerous area and grade of the impact during coal wining of hanging wall working face of step fault were comprehensively identified. The results show that the working face has a stress barrier effect during fault mining, and gradually forms a stress concentration in the mining plate. The barrier effect aggravates the accumulation of elastic strain energy and is an important factor inducing the occurrence of rock burst in the working face. During the mining period from the first fault to the next fault, the advance abutment stress of the working face is relatively small, but the energy in the roof area between the two faults increases, presenting a potential impact risk. When the working face is advancing towards the step fault, the subsidence deformation of the near-fault roof in front of the working face is easy to cause fault activation. When the working face is less than 20 m away from the fault, the step fault activation is obvious. The research results can provide reference for the prediction of rock burst and the division of dangerous areas, the layout of working face and the selection of mining sequence under the condition of similar step faults.

     

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