浅埋偏压对连拱隧道施工力学效应的影响及处治措施

Construction Mechanical Effect of Multi-arch Tunnel and Treatment Measures under Shallow Unsymmetrical Loading

浅埋偏压赋存条件是诱发连拱隧道大变形灾害的重要因素。以某浅埋偏压公路连拱隧道工程为背景,借助数值模拟方法对比研究不同开挖方案条件下偏压连拱隧道围岩、支护结构及曲中墙力学行为变化规律,并结合现场实测数据分析偏压洞口失稳灾害原因及处治措施。研究结果表明,围岩水平位移和竖向位移呈非对称分布,施工阶段埋深较大侧围岩变形受偏压荷载作用影响更为显著;不同开挖方案条件下中墙水平应力分布差异不明显,而竖向应力分布差异较大,中墙墙脚(拱脚)位置出现水平压应力集中现象;方案Ⅱ条件下隧道初期支护拱顶水平和竖向位移均约为方案Ⅰ的1.40倍以上,且方案Ⅱ更易引起埋深较大侧隧道中墙墙体因遭受附加偏压荷载作用而发生压裂破坏;针对浅埋偏压洞口大变形诱发原因,给出相应的防治措施,加固处治效果显著。研究成果可为浅埋偏压隧道施工变形控制和灾害防治提供科学参考。

The occurrence of shallow biased pressure is an important factor to induce the large deformation of multi-arch tunnel.Based on a shallow biased multi-arch tunnel project,the mechanical behavior of surrounding rock,support structure and middle wall of multi-arch tunnel under different excavation schemes were analyzed and compared by numerical simulation method,and combining with measured data the instability causes of portal section of biased multi-arch tunnel and its treatment measures was analyzed.The results show that the horizontal displacement and vertical displacement of surrounding rock are asymmetrically distributed,and the deformation of surrounding rock on the side with larger buried depth is more significantly affected by the action of unsymmetrical loading in the construction phase.The horizontal stress distribution of middle wall is not obvious,while the vertical stress distribution is quite different under different excavation schemes,and the phenomenon of horizontal compressive stress concentration occurs at the middle wall foot(arch foot).The vault horizontal and vertical displacements of primary support under the excavation schemeⅡare increased 1.40 times compared with the excavation schemeⅠ,and the excavation schemeⅡwill easily cause the middle wall on the side with larger buried depth suffer from additional unsymmetrical loading and even structural damage.According to the causes of large deformation of shallow biased tunnel,the corresponding prevention measures are proposed,and the effect of reinforcement is remarkable.The research results can provide reference for the deformation control and hazard prevention of shallow biased tunnel construction.