上下立交隧道施工优化与动态近接分区

Construction optimization and dynamic proximity zoning of upper and lower interchange tunnels

为优化在建交叉隧道施工顺序,对不同近接施工影响程度进行动态分区以便于施工管理。以在建的珠海大横琴山一号隧道与珠机城际隧道交叉段为工程背景,其中珠机城际隧道(断面小)在上方,而大横琴山一号隧道(断面大)在下方,应用数值仿真软件建立“先上后下”及“先下后上”2种施工工况模型。对比分析不同施工顺序下立交隧道纵向位移、横断面位移、拱顶沉降、仰拱位移、塑性区及支护结构应力等变化规律。讨论地层围岩位移分区准则与既有结构强度分区准则。研究后行隧道掌子面施工至交叉点不同距离时,先行隧道位移以及结构强度的动态分区情况,其中红区为特危险区、黄区为危险区、白区为注意区。研究结果表明:“先下后上”施工比“先上后下”施工要好;现场采纳了此方案,先施工下方大横琴山隧道,然后再施工上方珠机城际隧道。“先下后上”施工时,上部隧道开挖至交叉点前6 m至交叉点后12 m对下部隧道影响明显;并以下部隧道距中轴线前18 m至中轴线后10 m范围内作为特危险区,同时上部隧道开挖至距中轴线前后0.25D(D为开挖隧道跨度)范围内需加强监控量测,以保证隧道安全。“先上后下”施工时,以上部隧道距中轴线前27 m至中轴线后13 m作为特危险区,同时下部隧道开挖至距中轴线前1D至距中轴线后0.25D范围内时需加强监控量测,保证隧道安全。

In order to optimize the construction sequence of cross tunnels and carry out dynamic zoning of the impact of different adjacent construction to facilitate construction management,Dahengqinshan No.1 Tunnel and Zhuji intercity tunnel were taken as the engineering background.Zhuji intercity tunnel with a small cross section was above while Dahengqinshan No.1 tunnel with a large cross section was below.Two construction condition models of“top-down first”and“top-down first”were established by numerical simulation software program.The variation laws of longitudinal displacement,cross-sectional displacement,vault settlement,inverted arch displacement,plastic zone and support structure stress under different construction sequence were compared and analyzed.The dynamic zoning of the displacement and structural strength of the first advancing tunnel was investigated when the tunnel face of the latter tunnel is constructed to the intersection at different distances.The red zone was the special danger zone,the yellow zone was the danger zone,and the white zone was the attention zone.The results show that the construction of‘first down and then up’is better than that of“first up and then down”;this scheme is adopted at the site.The Dahengqinshan tunnel below is firstly constructed,and then the Zhuji intercity tunnel above.During the construction of“first down and then up”,the area from 18 m in front of the lower tunnel to 10 m behind the central axis is taken as the extremely dangerous area.At the same time,when the upper tunnel is excavated to 0.25D(D is the excavation tunnel span)before and after the central axis,the monitoring and measurement should be strengthened to ensure the safety of the tunnel.During the“up and down”construction,the upper tunnel should be 27 m in front of the central axis to 13 m behind the central axis as the extremely dangerous area.At the same time,when the lower tunnel is excavated to the range of 1D in front of the central axis to 0.25D behind the central axis,the monitoring and measurement should be strengthened to ensure the safety of the tunnel.