新建隧道上跨既有线的保护方案比选研究

Comparative Study on the Protection Schemes of New Tunnel Crossing Existing Line

随着城市地下空间开发的发展,新建隧道近接穿越既有隧道的工程屡见不鲜。通过合理的保护措施,控制既有线变形,保障既有线运营安全,是近接穿越施工中的关键问题。以滨海快线福州火车站~东门站区间隧道为工程依托,在FLAC3D数值分析平台上,对新建隧道上跨既有线全过程进行详细的数值模拟,重点关注既有线变形及地表沉降,并对3种保护方案进行比选。结果表明:盾构推进过程中,掌子面附近地表隆起,并随掌子面远去逐渐沉降;既有线拱顶隆起,随着掌子面靠近而逐渐增大,掌子面远离脱出后拱顶隆起回落。采用管幕隔离方案或新建隧道周围MJS注浆加固方案,均能有效减小近接施工对既有线的影响。既有线采用管幕隔离方案加固较没有采用管幕隔离方案,地表沉降减小29%,既有线拱顶位移减小21%;既有线采用周围MJS注浆加固方案较没有采用周围MJS注浆加固方案,地表沉降减小86%,既有线拱顶位移减小26%。综合考虑三种保护方案,推荐采用MJS注浆加固的保护方案。以上研究内容可为此类隧道的设计和施工提供借鉴和参考。

Newly built tunnels approaching to existing tunnels has become more and more popular with the fast development of urban underground space.Through reasonable protection measures,controlling the deformation and ensuring the operation safety of existing line are the key issues in the crossing over construction project.Considering the interval tunnel between Fuzhou Railway Station and Dongmen Station in Binhai Express line,the adjacent construction process of new tunnel crossing existing line is simulated inFLAC3D numerical platform.the deformation of existing line and the ground surface settlement,are well focused,and three protection schemes are then compared.The simulation results show that the ground near the tunnel face uplifts and gradually subsides with the tunnel face moves away.The vault uplift of the existing line gradually increases during the tunnel face approaching,and then falls gradually after the tunnel face leaving away.Both the MJS grouting around new tunnel and the pipe roof separation,can effectively reduce the impact on existing line.Compared to not using the pipe roof separation scheme,the existing line reinforced with the pipe roof separation experienced a 29%reduction in ground surface settlement and a 21%reduction in deformation of existing line.Similarly,compared to not using the MJS grouting around the new tunnel,the existing line reinforced with the MJS grouting around achieved an 86%reduction in ground surface settlement and a 26%reduction in deformation of the existing line.Taking into consideration the three protection schemes,the protection scheme of MJS grouting is recommended for this crossing over construction project.Thees researches can provide some reference for the design and the construction of similar projects.