连拱隧道施工过程中裂缝分布规律调查及产生原因分析

Investigation and analysis of crack distribution in the construction of multi-arch tunnel

在连拱隧道先行洞施工过程中,岩体开挖卸荷导致隧道围岩向临空面移动,致其拱顶上方和靠近后行洞一侧斜上方向围岩向先行洞临空面方向移动,进而引起围岩卸荷松动,降低岩土体的完整性和稳定性。随着后行洞开挖的进行,先行洞和后行洞相交的三角区域围岩产生二次扰动和卸荷松动,并向开挖一侧产生移动,其由于围岩移动所产生的荷载全部或部分转移到拱腰至拱肩位置的支护结构上,往往会在衬砌上产生数量不等、宽度不均、深度不同、方向各异的裂缝,使二衬出现张裂、压溃、错台等病害,严重影响了施工和运营过程中的交通安全。基于对现场施工过程中的裂缝分布、范围、数量、类型、深度、宽度随施工变化过程中的分布规律展开调查,确定裂缝的形成原因和分布规律,并结合监控量测数据和数值分析结果,阐明裂缝产生的机理,为防止隧道裂缝的发生和隧道施工措施的处置提供理论依据。

During the construction of the advance tunnel of the double arch tunnel,the excavation and unloading of the rock mass causes the surrounding rock of the tunnel to move towards the free surface,which causes the surrounding rock above the vault and the inclined upward direction near the side of the back tunnel to move towards the free surface of the advance tunnel,and then causes the unloading and loosening of the surrounding rock,which reduces the integrity and stability of the rock and soil mass.In the process of tunnel excavation,the surrounding rock in the triangle area where the first tunnel and the second tunnel intersect produces secondary disturbance and unloading loosening,and moves to one side of the excavation.As the surrounding rock moves,all or part of the load is transferred to the support structure from the waist to the shoulder of the arch,there are often cracks with different quantity,width,depth and direction on the lining.The cracks make the secondary lining crack,collapse,dislocation and other diseases,which seriously affect the traffic safety in the construction and operation process.Based on the investigation of crack distribution,scope,quantity,type,depth and width in the process of site construction,the formation reason and distribution rule of cracks are determined,and the mechanism of crack production is clarified in combination with monitoring measurement data and numerical analysis results,so as to provide theoretical basis for the prevention of tunnel cracks and the treatment of tunnel construction measures.