不同侧覆土厚度条件下连拱隧道的偏压特性研究

Study on bias characteristics of multi arch tunnel under different side overburden thickness

起凤山隧道进、出口浅埋偏压严重,上覆土层较薄,稳定性差,开挖扰动后上部土层易发生滑动.后行洞开挖时常会出现围岩变形过大、坍塌、失稳等安全事故.本文结合现场连拱隧道的地质条件和围岩的力学特点,采用理论分析和数值模拟方法对开挖后连拱隧道埋深、侧覆土层厚度与围岩应力和位移的变形规律展开研究,研究结果表明:隧道在竖向方向受到的偏压应力随着埋深的增加而减小,埋深越浅其偏压作用越明显,当埋深超过20 m后偏压作用的偏压应力增加量逐渐减小.对不同侧覆土层厚度的隧道开挖引起的岩体竖向变形特性进行分析,结果表明:竖向位移随侧覆土层厚度的增加逐步减小,当侧覆土厚度超过21 m时,竖向位移受侧覆土厚度的影响较小,基本只受围岩本身岩土性质的影响.

The Qi Feng tunnel entrance and exit shallow buried bias is serious,the overlying soil layer is thin,and the stability is poor.After the excavation disturbance,the upper soil layer tends to slide.The excavation of back holes often causes large deformation,collapse and instability of surrounding rock.In this paper,combined with the geological conditions of the multi arch tunnel and the mechanical characteristics of surrounding rock,the theoretical analysis and numerical simulation are used to study the deformation law of the buried depth,side cover soil thickness and the stress and displacement of the surrounding rock after excavation.The results show that the bias stress of the tunnel under the vertical direction increases with the depth of the buried tunnel.The bias stress of the tunnel in the vertical direction decreases with the increase of the buried depth.The more shallow the buried depth is,the more obvious the bias effect is.When the depth of burial exceeds 20m,the increased amount of bias stress is gradually reduced after the bias is applied.The vertical deformation characteristics of the rock mass caused by tunnel excavation with different thickness of the tunnel are analyzed.The vertical displacement is gradually reduced with the increase of the thickness of the side covering layer.When the thickness of the overlying soil is more than 21m,the vertical displacement is less affected by the thickness of the side cladding soil,basically only by the surrounding rock itself.