浅埋偏压小净距隧道施工扰动空间效应研究

Spatial mechanical effect of disturbance in shallow tunnel construction with bias pressure and small clearance distance

为揭示浅埋偏压小净距隧道施工对隧道围岩的扰动规律,以义东高速防军隧道为工程背景,基于有限元软件MIDASGTSNX建立隧道进口小净距段三维模型并分析其空间效应,采用预留核心土法模拟隧道洞口段动态施工过程,研究了隧道围岩位移场和应力场演化特征与规律。结果表明:隧道开挖后,地表沉降呈现明显的非对称现象且先行洞和后行洞开挖前期对地表沉降位移影响较大;隧道开挖面空间约束的作用范围为开挖面前后1~1.5倍洞径;开挖面前后0.5倍洞径范围为强影响区,0.5~1倍洞径范围为弱影响区;后行洞开挖对围岩主应力偏压比影响较小,后行洞开挖后拱脚位置受偏压影响较大,隧道施工时应及时封闭支护结构,还应对应力集中位置重点监测。

In order to understand the disturbance effect of shallow-buried bias voltage and small clearance distance tunnel construction on tunnel surrounding rock,taking the Yidong High-speed Defense Army Tunnel as the engineering background,a three-dimensional model of the tunnel entrance small clearance distance section is established based on the finite element software MIDAS GTS NX,and its spatial effect is analyzed.The dynamic construction process of the tunnel entrance section is simulated using the reserved core soil method,and the displacement field and stress field evolution characteristics and laws of the tunnel surrounding rock are studied.The research results show that after tunnel excavation,the ground settlement shows obvious asymmetry,and the pre-excavation of the leading and trailing tunnels has a greater impact on the ground settlement displacement.The spatial constraint range of the tunnel excavation face is 1~1.5 times the tunnel diameter in front and behind the excavation face,and the range of 0.5 times the tunnel diameter in front and behind the excavation face is the strong influence zone,while the range of 0.5~1 times the tunnel diameter is the weak influence zone.The influence of the trailing tunnel excavation on the main stress bias ratio of the surrounding rock is relatively small,but the position of the arch foot is greatly affected by the bias after the trailing tunnel excavation.The support structure should be closed in a timely manner during tunnel construction,and the stress concentration position should be monitored.