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急倾斜煤岩互层巷道变形特征及机理研究

Study on deformation characteristics and deformation mechanism of steep coal rock interbedded roadway

  • 摘要: 针对急倾斜煤岩互层巷道的变形问题,采用现场实测与数值模拟实验方法,运用围岩稳定性联合监测设备,分析急倾斜煤岩互层巷道围岩裂隙分布特征、锚杆拉力变化、巷道变形及其应力分布规律。结果表明:B8急倾斜煤岩互层巷道的平均水平主应力24.3 MPa,约为垂直地应力3.08倍。当岩层过渡到煤层后其孔壁较为破碎,随钻孔深度增加孔壁逐渐产生剪切错动。急倾斜煤岩互层巷道存在非对称性的变形特征,南帮帮鼓0.60~1.00 m大于北帮的0.20~0.40 m,两帮变化呈现出“收敛期-趋于稳定期-稳定期”的阶段性趋势,其巷道“收敛期”存在5 d左右的蠕变特征,单日变形量为0.10~0.20 m,为此施工作业应避开巷道的5 d左右的收敛期。返修阶段的巷道变形对锚杆造成破坏,使得南帮锚杆锚固力30 kN时被拉出,至巷道变形稳定相对后,90处锚杆中共有15处存在锚杆质量较低的情况,占比达到16.67%。由于急倾斜煤岩层地质因素的影响,巷道围岩的垂向裂隙较为发育,在水平应力的作用下,软弱夹层极易发生结构面间的错动变形,加之岩层内部的挤压力作用,继而产生岩层的离层变形,最终导致巷道南帮帮鼓大变形现象。两帮呈现巷道底鼓南高北低的不对称变形特征,南帮变形失稳后,使得巷道北帮岩层承受覆岩作用较大,应力集中效应较强。研究结果为急倾斜煤岩互层巷道的变形控制提供了科学依据。

     

    Abstract: In view of the deformation problem of steeply inclined coal-rock interbedded roadway, the field measurement and numerical simulation experiment methods were adopted, and the surrounding rock stability joint monitoring equipment was used to analyze the distribution characteristics of surrounding rock cracks, the change of bolt tension, the deformation of roadway and its stress distribution law in steep coal-rock interbedded roadway. The results show that the average horizontal principal stress of the B8 steeply inclined coal-rock interbed roadway is 24.3 MPa, which is about 3.08 times of the vertical in-situ stress. When the rock layer transitions to the coal seam, the hole wall is relatively broken, and the hole wall gradually produces shear dislocation with the increase of the drilling depth. The steeply inclined coal-rock interbedded roadway has the characteristic of asymmetric deformation, and the heave of the south is 0.60-1.00 m, which is larger than that of the north. The changes of the two sides show a phased trend of "convergence period- nearly stable period-stable period". The "convergence period" of the roadway has the creep characteristic of about 5 days, and the daily deformation is 0.10-0.20 m. Therefore, the construction operation should avoid the convergence period of about 5 days in the roadway. The deformation of the roadway in the repairing stage caused damage to the bolts, causing the bolts to be pulled out when the anchoring force of the south side bolt was 30 kN. After the roadway deformation was stable and relatively stable, 15 of the 90 bolts had low quality bolts, accounting for 30 kN, which reached up to 16.67%. Due to the influence of geological factors in the steeply inclined coal stratum, the vertical cracks of the surrounding rock of the roadway are relatively developed. Under the action of horizontal stress, the weak interlayer is prone to dislocation and deformation between structural planes. The layer separation deformation of the rock stratum occurs, which eventually leads to the large deformation of the roadway.. The two ribs present the characteristics of asymmetrical deformation of the roadway floor heave that is high in the south and low in the north. After the deformation and instability of the south side, the rock strata of the north side of the roadway is subjected to greater overburden and stronger stress concentration effect. The research results provide a scientific basis for the deformation control of the steeply inclined coal-rock interbedded roadway.

     

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