大断面隧洞上穿既有隧洞结构安全分析

为分析丽水机场沙溪排水隧洞上穿既有玉溪引水隧洞工程可能造成的影响,采用有限元模拟法,综合考虑了大断面隧洞开挖引起的围岩应力重分布和爆破振动影响,研究了新建大断面隧洞自身的围岩受力和变形特征,及新建隧洞开挖、爆破施工引起的既有隧洞衬砌受力变形及动力响应。结果表明,在完成开挖后,新建排水隧洞的最大位移发生在拱顶处,围岩及衬砌结构受力变形满足设计要求;既有隧洞沿竖向发生隆起变形,最大隆起量为6.3mm,横向拱腰处发生向内的水平位移,最大水平位移为0.76mm,最大值均发生在隧洞交叉点处;既有隧洞衬砌结构最大压应力为30MPa,无拉应力,满足衬砌结构抗压和抗拉强度要求;新建隧洞爆破施工导致既有隧洞的最大质点振动速度满足爆破安全规程规定,说明新建大断面隧洞采用分层分块小断面控制爆破施工技术可有效控制爆破施工对临近结构的影响。

Structural Safety Analysis of Large Section Tunnel Passing Through Existing Tunnel

To analyze the possible impact on the existing Yuxi diversion tunnel caused by the Shaxi drainage tunnel of Lishui airport passing over,finite element analysis is used to study the stress and deformation characteristics of surrounding rock of the new large section tunnel and the stress deformation and dynamic response of the existing tunnel lining caused by the excavation and blasting construction of the new tunnel,with considering the stress redistribution of surrounding rock and the impact of blasting vibration caused by the excavation of large section tunnel.The results show that after the excavation,the maximum displacement of new construction drainage tunnel occurs at the vault,and the stress and deformation of the surrounding rock and lining structure meet the design requirements.The existing tunnel is uplifted along the vertical direction with the maximum uplifted amount of 6.3mm.The horizontal displacement is inward at the transverse arch waist with the maximum horizontal displacement of 0.76mm.The maximum value occurs at the intersection of the tunnel.The maximum compressive stress of the existing tunnel lining structure is 30MPa,no tensile stress,which meets the requirements of the compressive and tensile strength of the lining structure.The blasting construction of the new tunnel results in the maximum particle vibration speed of the existing tunnel meeting the requirements of the blasting safety regulations,which indicates that the blasting construction technology of the new large section tunnel with layered and block small section control can effectively control the impact of the blasting construction on the adjacent structures.