Based on the continuity hypothesis and Mohr-Coulomb criterion, a criterion to evaluate whether rock mass slippage along a structure surface will occur or not is proposed for a circular tunnel adopting the elastic mechanics method, and the minimum slippage zones of the rock mass under different internal friction angels of the structural surface are predicted. The proposed criterion is verified by the shear displacements of the rock mass along the structural surface with different internal friction angles through UDEC. The impact factors on the minimum internal friction angle to keep the rock mass stable and prevent slippage-including the lateral pressure coefficient, dip angle of the structural surface and the vertical distance from the tunnel center to the structural surface-and the mathematical relation among them are determined, and the impact law for the three factors on the minimum internal friction angle is analyzed. The results show the lateral pressure coefficient, the dip angle of the structural surface mainly influence the minimum internal friction angle of the structural surface that is far from the tunnel and required by keeping the rock mass stable, and the vertical distance only effects the minimum internal friction angle of the structural surface close to the tunnel excavation boundary but has no obvious effect on the region at a distance of more than 2.5 times the excavation radius.%文章利用弹性力学方法,在连续性假设和Mohr-Coulomb滑移准则基础上,推导了圆形隧道围岩沿结构面滑移的判定条件,并预测了结构面不同内摩擦角情况下的围岩最小滑移区域.利用离散元数值方法对该判据进行了验证,结合不同内摩擦角下的结构面剪切位移,证明了该判据的合理性;确定了保持圆形隧道围岩稳定而不出现滑移所需的结构面最小极限内摩擦角的影响因素及其数学关系,其影响因素包括侧压力系数、结构面倾角、以及隧道圆心到结构面垂距,并分析了上述3个因素对结构面最小极限内摩擦角的影响规律.结果表明:侧压力系数和结构面倾角主要影响远离隧道部位为保持围岩稳定所需的结构面最小极限内摩擦角,而垂距只影响靠近隧道开挖边界部位结构面的最小极限内摩擦角,对超过2.5倍开挖半径的区域影响效果不明显.研究结果可对含结构面岩体中隧道加固提供参考.
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