基于强度折减法的浅埋偏压隧道——边坡联合地层稳定性研究

Research on Formation Stability of Shallow Buried Partial Pressure Tunnel and Slope based on Strength Reduction Method

为了解决当浅埋偏压段的隧道与软弱夹层相交时,边坡与隧道联合地层稳定性安全问题,通过理论分析和FLAC 3D有限差分数值模拟方法研究了在基于抗剪强度折减法的理论基础下,将抗拉强度进行折减,即抗拉剪强度同步折减法,采用该理论对不同软弱夹层倾角和不同软弱夹层与隧道的相对位置下进行模拟,分析边坡与隧道联合地层的安全系数变化规律和塑性区发展过程。结果表明:地层的失稳形式主要分为受隧道稳定性控制和受隧道稳定性和边坡稳定性共同控制两种。且在考虑抗拉剪强度同步折减下,由隧道底部产生的剪切屈服区和地表顶部的张拉屈服区发生贯通相连,边坡逐渐失稳滑移。修正后的M-C准则因考虑了抗拉强度的折减,更符合岩土体破坏类型,结果较M-C准则更为准确。

In order to solve the problem of the stability and safety of the combined stratum of the slope and tunnel when the tunnel in the shallow buried and shallow unsymmetrical pressure section intersects with the weak interlayer,the tensile strength is reduced based on the theory of shear strength reduction,namely the synchronous reduction of tensile shear strength,through theoretical analysis and FLAC 3D finite difference numerical simulation method,This theory is used to simulate different dip angles of soft interlayer and different relative positions of soft interlayer and tunnel,and analyze the variation law of safety factor of slope and tunnel combined stratum and the development process of plastic zone.The results show that the formation instability can be divided into two types:tunnel influence and tunnel and slope influence.Considering the synchronous reduction of tensile shear strength,the shear yield zone generated at the bottom of the tunnel is connected with the tensile yield zone at the top of the surface,and the slope gradually loses stability and slides.The modified M-C criterion is more accurate than the M-C criterion because it considers the reduction of tensile strength,which is more consistent with the failure type of rock and soil mass.