A study of the mechanism and regularity of failures in the surrounding rock of a deep buried bias tunnel embedded in geologically bedding strata: taking one tunnel of the Zhengwan line as an example
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摘要:
处于薄—中层倾斜层状岩体中的深埋隧道常会产生地质顺层偏压的问题，导致隧道局部塌方、偏压变形及支护结构破坏。本文以郑万线某隧道为例，采用理论分析、数值模拟方法对深埋顺层隧道的破坏机理及不同结构面参数下的破坏规律展开了研究。研究结果表明：（1）深埋顺层偏压隧道洞周围岩将根据其切向应力与结构面夹角的不同发生岩层拉裂破坏、结构面剪切破坏及岩体自身破坏，其中切向应力与结构面平行位置，即反倾侧拱腰及顺倾侧拱脚位置主要发生拉裂破坏，此处围岩塑性区范围最广，围岩位移最大，围岩处于极不稳定状态；（2）顺层偏压隧道的破坏规律与结构面强度参数有直接关系，围岩塑性区范围及围岩位移均随着结构面摩擦角的增大而降低，且降低趋势逐渐放缓，当结构面摩擦角达到岩体摩擦角后，结构面摩擦角继续增加对围岩稳定性影响较小；（3）围岩塑性区及围岩位移场偏压分布特征随结构面倾角的变化而整体旋转，且对于隧道底部而言，结构面最不利倾角为0°，此时隧底最大上鼓量大于其他倾角下的最大上鼓量；对于隧道拱部而言，最不利倾角为40°，此时洞周最大收敛值大于其他倾角下的最大收敛值，最不利位置位于反倾侧拱腰。
Abstract:Deep buried tunnels embedded in geologically bedding thin to medium thick strata often have the bias problem of geological bedding, which leads to partial collapse, bias deformation and support structure damage of tunnels. This paper takes one tunnel of the Zhengwan line as an example and examines the mechanism and regularity of failure in tunnels embedded in geologically bedding strata by using the methods of theoretical analysis and numerical simulation. The result show that (1) the surrounding rocks of the deep buried tunnel embedded in geologically bedding strata will undergo tensile fracture of rocks, shear failure of structural plane and failure of rock mass according to the angle between the tangential stress and structural plane. The tangential stress is parallel to the structural plane, and the tensile fracture of rocks mainly occurs. A the plastic zone of surrounding rock here is the widest, the displacement of surrounding rock here is the largest, and the surrounding rock is in an extremely unstable state. (2) The failure regularity of the tunnels embedded in geologically bedding strata is directly related to the strength parameters of the structural plane, the range of plastic zone and displacement of the surrounding rock decreases with the increasing friction angle of the structural plane, and the decreasing trend slows down gradually. When the friction angle of the structural plane exceeds the friction angle of rock mass, the continuous increase in the friction angle of the structural plane has little effect on the stability of the surrounding rock. (3) The bias distribution characteristics of the plastic zone and the displacement of the surrounding rock rotates wholly with the change in the dip angle of the structural plane, and for the bottom of the tunnel, the most unfavorable inclination of the structural plane is 0°, the maximum heave of the tunnel bottom is greater than that under other dip angles; for the tunnel arch, the most unfavorable inclination of the structural plane is 40°, the maximum convergence value around the tunnel is greater than that under other dip angles, and the most unfavorable position is at the inverted arch waist.
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