红层盾构隧道交叠下穿运营地铁隧道影响分析

Analysis on the influence of shield tunnels in red stratum overlapping and underneath passing existing subway tunnels

针对红层新建地铁盾构隧道与既有隧道长距离交叉下穿时,既有隧道的变形问题,以长沙市轨道交通3号线下穿长沙地铁1号线工程为背景,采用FLAC3D有限元差分软件进行数值模拟,结合实测数据,研究施工参数对地层变形和既有隧道变形的影响。研究结果表明:土仓压力增大,有助于减小不均匀沉降,沉降差值比随着土仓压力的增大逐渐趋于平稳。土仓压力在0.24 MPa附近变动时,既有隧道的轨向不均匀沉降模式发生较明显的改变。随着同步注浆压力的增大,交叉点处拱底竖向位移值逐渐减小,且轨向不均匀沉降差值比与同步注浆压力成正比。分析土仓压力和注浆压力对既有隧道轨向不均匀沉降的影响规律,建议土仓压力值范围为0.08-0.13 MPa,注浆压力值范围为0.2-0.5 MPa。通过实测数据分析表明:土仓压力和注浆压力取建议值时,各监测断面盾构掘进过程中,管片和轨道板的不均匀沉降均在控制范围内,该结果可为类似工程施工提供参考。

In order to control the deformation of existing metro tunnel induced bythe long distance overlapping and underneath passing new metro shield tunnel in red stratum,based on the project of the line 3 underpass the line 1 of the rail transit in Changsha,the FLAC3D finite difference software was used for numerical simulation, combining with monitoring data, the influence of construction parameter on the deformation of stratum and existing tunnel. The results show that,with the increase of the chamber earth pressure,the uneven settlement can be reduced,and the settlement difference ratio gradually tends to be stable. The uneven settlement of the existing tunnel in the rail direction changes significantly, when the soil bunker pressure fluctuates around 0.24 MPa. With the increase of synchronous grouting pressure,the vertical displacement of arch bottom at intersection point decreases gradually,and the difference ratio of uneven settlement in rail direction is proportional to the synchronous grouting pressure. The recommended value of the chamber earth pressure is 0.08- 0.13MPa,and the value of synchronous grouting pressure is 0.2-0.5 MPa,resulted from the analysis of the influence of chamber earth pressure and grouting pressure on uneven settlement of existing tunnel rail. The uneven settlement of segment and track slab at monitoring section is within the control range during shield tunneling, when the chamber earth pressure and grouting pressure are calculated according to the recommended value that is got from the monitoring data analysis. The results can provide reference for similar project.