软土场地深大基桩近距离试桩对既有地铁隧道影响分析

Analysis of Influence of Short Distance Test Pile on Existing Subway Tunnel in Soft Soil Field

本文在实测和理论分析的基础上,对杭州软土地基某工程深大试桩对邻近隧道影响进行了分析。研究了桩-隧距、套管成桩工艺等因素对既有地铁隧道位移变化的影响,以及施工后的发展变化规律和主要影响因素。大直径基桩施工会使邻近隧道产生位移,合理选择套管成孔方式对邻近隧道的影响远小于成桩后期的影响;套管拔出会明显增加邻近隧道在基桩施工期间及工后的位移;套管成孔阶段与成桩阶段的隧道最大水平位移变化量、成桩全过程的隧道最大沉降量与桩-隧距呈明显负相关趋势。当桩隧-距/桩长≤0.2时,宜采用全套管工艺进行大直径基桩施工,其中桩隧-距/桩长小于0.08时,可保留套管;桩隧-距/桩长在0.2~0.33时,可采用半套管工艺进行施工。

On the basis of actual measurement and theoretical analysis,the influence of a deep test pile on the adjacent tunnel of a project in Hangzhou soft soil foundation was analyzed.The influence of factors such as pile-tunnel distance and casing pile forming technology on the displacement change of existing subway tunnel were studied,as well as the development and change rule after construction and the main influencing factors were analyzed.The construction of large diameter foundation piles cause the displacement of near neighbor tunnel.The influence of reasonable selection of casing perforation method on adjacent tunnel is much less than that in the late stage of pile formation.The removal of casing will obviously increase the displacement of adjacent tunnel during and after foundation pile construction.The maximum horizontal displacement of the tunnel in the stage of casing hole formation and pile formation and the maximum settlement of the tunnel in the whole process of pile formation are negatively correlated with the pile-tunnel distance.When the piletunnel distance/pile length is less than 0.2,it is appropriate to adopt the whole casing technology for large-diameter foundation pile construction.When the pile tunnel distance/pile length is less than 0.08,the casing can be retained.When the pile tunnel-distance/pile length is between 0.2 and 0.33,the half-casing technology can be used for construction.