倾斜层状节理岩体隧道开挖围岩应力拱效应研究

    Research on stress arching effect of surrounding rock in excavation of inclined layered jointed rock mass tunnels

    • 摘要: 地下工程岩体开挖应力拱效应对地下开挖空间的围岩自稳具有重要影响。针对倾斜层状节理岩体隧道的围岩应力拱效应,利用二维离散元程序(UDEC)开展一系列数值试验模拟隧道开挖后围岩应力拱特征,通过对比室内模型试验结果验证数值程序正确性,进而研究不同的岩层倾角、单一块体尺寸和侧压系数条件下围岩应力拱区的变化规律,同时结合砌体梁结构力学模型和推力线理论,讨论这些影响因素对倾斜层状节理围岩应力拱形成的作用机理。研究结果表明,倾斜层状节理岩体隧道顶板应力拱区的轴线方向大致与倾斜的层理面垂直,且随岩层倾角的增加而逆时针旋转;当岩层倾角超过60°时,应力拱效应基本消失,隧道顶部两个层理面间的块体群倾向于发生整体性滑落;应力拱区随单一块体尺寸和侧压系数的增加而近似线性减小;节理岩层推力线的拱度随上覆荷载和岩层跨度的增加而增大,而提高作用于岩层的水平推力会降低推力线拱度,有利于砌体梁结构稳定和应力拱形成。研究结果可为节理岩体隧道开挖稳定性评估与控制提供理论支持。

       

      Abstract: The stress arching effect of rock excavation in underground engineering has an important influence on the self-stability of the surrounding rock in the underground excavation space. Aiming at the stress arching effect of surrounding rock in inclined layered jointed rock mass tunnel, a series of numerical tests are carried out using a two-dimensional discrete element program (UDEC) to simulate the stress arching characteristics of surrounding rock after tunnel excavation. The correctness of the numerical program is verified by comparing the results of laboratory model tests, and then the variation of stress arch zone of surrounding rock is studied under different strata inclination angle, single block size and lateral pressure coefficient. At the same time, the mechanism of these factors on the stress arching of the surrounding rock of inclined layered joint is discussed based on the structural mechanics model of masonry beam and the thrust line theory. The results show that the axial direction of the stress arch of the roof of the inclined layered jointed rock mass tunnel is roughly perpendicular to the inclined bedding plane, and it rotates counterclockwise with the increase of the inclination angle. When the inclination angle of the strata is more than 60°, the effect of the stress arch basically disappears, and the block group between two laminar surfaces at the top of the tunnel is inclined to undergo a monolithic sliding. The stress arch zone decreases approximately linearly with the increase of single block size and lateral pressure coefficient. The camber of the thrust line of the joint stratum increases with the increase of overlying load and the span of the stratum, but increasing the horizontal thrust on the stratum will reduce the camber of the thrust line, which is conducive to the stability of the masonry beam structure and the stress arch. This study can provide theoretical support for the stability assessment and control of tunnel excavation of jointed rock mass.

       

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