土岩复合地层中基坑施工对下卧既有隧道变形和裂缝影响的实测与分析

Field Measurement&Analysis of Influence of Foundation Pit Construction on Deformation&Cracks of Underlying Existing Tunnel in Soil Rock Composite Stratum

随着城市建设的发展,基坑工程和既有隧道交叉建设的情况越来越多,控制既有隧道的变形和裂缝发展成为基坑施工的关键。结合上跨既有轨道交通L1的厦门第二西通道工程现场实测数据,研究土岩复合地层中深基坑开挖对下卧既有隧道竖向位移、水平位移、收敛变形和裂缝宽度的影响规律。结果表明:基坑卸荷率与隧道隆起量之间近似呈指数关系,地表堆载导致既有隧道在一定区域内发生沉降;隧道水平位移受到横向刚度的影响具有"转体效应";隧道在竖向隆起段的收敛变形为"竖鸭蛋"形态,且在竖向位移曲线拐点处发生突变;下卧隧道变形的3D特性显著,应根据隧道绝对裂缝宽度调整其他变形控制指标。

With the development of urban construction,there are more&more cross construction of foundation pit engineering&existing tunnel.Controlling the deformation&crack development of existing tunnel has become the key of foundation pit construction.Combined with the field measured data of Xiamen Second West Channel Project spanning the existing Rail Transit L1,the influence of deep foundation pit excavation on the vertical displacement,horizontal displacement,convergence deformation and crack width of the underlying existing tunnel in soil rock composite stratum is studied.The results show that there is an exponential relationship between the unloading rate of foundation pit and the uplift of tunnel,and the surface surcharge leads to the settlement of existing tunnel in a certain area;the horizontal displacement of the tunnel is affected by the transverse stiffness,which has the rotation effect;the convergence deformation of the tunnel in the vertical uplift section is in the shape of vertical duck egg,and there is a sudden change at the inflection point of the vertical displacement curve;the 3D characteristics of the deformation of the underlying tunnel are significant,and other deformation control indexes should be adjusted according to the absolute crack width of the tunnel.