基坑开挖对旁侧既有隧道影响的模型试验研究

Model test study on the effect of foundation pit excavation under single soil layer on existing tunnels

研究基坑开挖对旁侧既有隧道的影响并制定合理的隧道变形及位移控制措施,是当前城市地下空间开发利用过程中的重要课题之一。文章运用模型试验及数值分析相结合的方法,分析了基坑开挖卸载作用下隧道的内力、位移及土压力变化规律和埋入式隔离桩体系对于既有隧道的保护作用。结果表明:基坑开挖导致隧道呈现两端拉伸,上、下压缩的变形趋势,且隧道埋深越浅、距离基坑越近,隧道变形趋势越大;隧道整体发生朝向基坑一侧的位移,距离基坑较近及埋深较浅的隧道位移较大;靠近基坑一侧的隧道围土压力减小,远离基坑一侧的隧道围土压力增大;长度在基坑嵌固深度上、下的隔离桩体系对隧道有很好的保护作用,但长度过长导致效费比不高,长度未超过基坑开挖时的隔离桩体系对隧道的保护作用有限。

It is one of the most important tasks in the development and utilization of urban underground space to study the influence of foundation pit excavation on the side existing tunnels and to formulate reasonable deformation and displacement control measures.Using the method of model test and numerical analysis,this paper studies the internal force,displacement and earth pressure of the tunnel under the action of excavation and unloading of foundation pit,and the protective effect of the embedded isolation pile system on the existing tunnel.The results show that the excavation of the foundation leads to the deformation trend of tension and compression at both ends of the tunnel.The shallower the buried depth of the tunnel is,the closer it is to the foundation pit,the greater the deformation trend of the tunnel.The displacement of the tunnel towards the side of the foundation pit occurs as a whole.The displacement of the tunnel near the pit and shallower buried depth is larger,the surrounding earth pressure of the tunnel close to the pit decreases,and the surrounding earth pressure of the tunnel far away from the pit increases.The separation pile system with the length above and below the embedded depth of the pit has a good protection effect on the tunnel,but the length is too long.The long-term cost ratio is not high and the length of the isolated pile system is no longer than the excavation of the foundation pit.