大断面小净距公路隧道施工影响分析

以佛羊岭隧道工程为研究背景,采用上下台阶法进行施工,以FLAC3D有限元软件为计算平台,建立大断面小净距公路隧道有限元模型,对隧道模型进行数值模拟分析。研究地表沉降、围岩与衬砌结构应力,并提出相应的监控和加固对策。数值分析结果表明:先行隧洞上部地表沉降比后行隧洞大,后行隧洞的施工会增大先行隧洞竖向位移,使先行洞的最大主应力和最小主应力出现不同幅度的增加,隧道衬砌结构应力集中于拱腰至拱脚范围区域,先行洞支护结构对于后行洞开挖起到稳定岩体的作用,后行隧道的开挖会使中夹岩柱出现应力集中,在施工时应注意对隧道围岩采取加固措施。分析结果能够为大断面小净距公路隧道的设计和施工提供科学依据。

Impact analysis on construction of large section and small spacing road tunnel

The construction project of Fo Yangling Tunnel was taken as the research background, the construction was carried out by using benching tunneling construction method. The fast Lagrangian analysis of continua 3D (FLAC3D) finite element software was used as the calculation platform to establish the finite element model of tunnel with large section and small clear distance. The tunnel model was numerically simulated and subsidence, stress of surrounding rock and lining structural were analyzed. And the corresponding monitoring and reinforcement measures were put forward. The results of numerical analysis showed that the settlement of the upper part of the advance tunnel was larger than the subsequent tunnel. The construction of the subsequent tunnel increased the vertical displacement of the advance tunnel, which caused the increase of maximum principal stress and the minimum principal stress. The stress of tunnel lining structure was concentrated in the area from arch waist to arch foot. The support structure of advance tunnel played the role of stabilizing rock mass in the excavation of subsequent tunnel, and the excavation of the subsequent tunnel would make the stress concentration of the middle rock. In the construction, attention should be payed to the surrounding rock and reinforcement measures should be taken. The analysis results could provide a scientific basis for the design and construction of large section and small spacing road tunnel.