基于锚固力学效应巷道围岩稳定性分析

Stability analysis of surrounding rock under anchorage mechanics effect

  • 摘要: 为了分析巷道在锚杆支护时锚杆和围岩耦合作用下形成的锚固承载层对巷道围岩稳定性的影响,根据围岩应力分布曲线特点,将巷道围岩划分为塑性区和弹性区进行研究。结合Mohr-Coulomb准则,分析锚杆在施加预紧力时引起容重的变化,可求解得到锚固承载层范围内切向应力的解析表达式,由静力平衡方程推导计算出锚固承载层外边界所能提供的等效支护力以及在等效支护力作用下巷道围岩塑性区的应力、半径和巷道位移计算解析表达式。通过上述所求的计算解析表达式结合全长锚固锚杆的预紧力、长度、间排距来分析3者对巷道围岩的力学效应影响。研究结果表明:等效支护力对巷道围岩的稳定性有一定的影响,在等效支护力的作用下,对巷道围岩应力分析可知,围岩应力峰值发生变化,且位置向巷道壁转移;全长锚固锚杆预紧力越大,锚杆长度越长,间排距越密,锚固承载层范围内的等效支护力越大,对巷道围岩的稳定性越有利;锚固承载层厚度与等效支护力的大小成正比,随着等效支护力的增大,巷道围岩的塑性区范围和巷道表面位移都会明显下降,等效支护力对围岩的稳定性有着很好的抑制作用。通过FLAC3D数值模拟对理论分析结果加以验证,根据模拟锚固承载层作用下的塑性区半径和巷道表面位移分析可知,数值模拟与理论分析结果基本一致。

     

    Abstract: In order to analyze the influence of anchor bearing layer formed under the coupling effect of anchor and sur- rounding rock on the stability of roadway surrounding rock,the surrounding rock was divided into plastic zone and elas- tic zone according to the stress distribution curve of surrounding rock. Combined with Mohr-Coulomb criterion,in ana- lyzing the change of volume force caused by bolt pre-tightening force,the analytical expression of the tangential stress within anchor bearing layer can be obtained. From the static equilibrium equation,it can derive the equivalent support- ing force provided by the anchor bearing layer boundary and the calculation analytical expression of the stress,radius and roadway displacement within the plastic zone of roadway surrounding rock under the action of equivalent supporting force. The mechanical effects of the pre-tightening force,length and row spacing of the full-length anchor bolt on roadway sur-rounding rock were analyzed by the above calculated analytical expressions. The results show that the equiv-alent support force has a certain influence on the stability of roadway surrounding rock. Under the effect of the equivalent support force,the stress analysis of roadway surrounding rock shows that the stress peak value of surround- ing rock changes and the position shifts to the roadway wall. The greater the pre-tightening force of the full-length an- chorage bolt,the longer the length of the bolt and the denser the row spacing,and the greater the equivalent support force within the range of the anchorage bearing layer,the better the stability of the roadway surrounding rock. The thickness of anchor bearing layer is proportional to the size of the equivalent support force. With the increase of the e- quivalent support force,the plastic zone range and surface dis-placement of roadway surrounding rocks will decrease significantly,and the equivalent support force has a good inhibitory effect on the stability of surrounding rocks. The theoretical analysis results were verified by FLAC3D numerical simulation. According to the plastic zone radius and roadway surface displacement anal-ysis under the action of the simulated anchorage bearing layer,the numerical simu- lation results were basically consistent with the theoretical analysis results.

     

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