盾构隧道重叠下穿地铁隧道施工变形规律研究

Study on construction deformation law of shield tunnel overlapping through the subway tunnel

为研究近接重叠下穿既有隧道的盾构施工对地表和既有隧道的影响,以长沙地铁3号线下穿地铁1号线的盾构隧道工程为依托,采用Midas/GTS NX软件建立三维模型,考虑土仓压力、注浆压力、注浆量和掘进速度影响下,探究新建隧道施工对地表沉降和既有隧道位移的影响。研究结果表明:土仓压力增大会减少地表沉降量,且掌子面前、后各3.5倍隧道洞径区间内完成了90%的竖向变形;增大注浆压力和注浆量均可减少既有隧道的竖向位移,但注浆量对既有隧道竖向变形的控制作用较注浆压力的大,当研究区间的注浆压力和注浆量分别提高了1.5倍、0.6倍时,既有隧道竖向变形分别降低了0.5、0.9 mm;盾构掘进速度增大,地层所受扰动增大,地表最大沉降量和既有隧道最大竖向位移也增大。研究成果可为类似工程施工提供技术指导。

In order to study the influence of shield construction on the surface and existing tunnel,based on the shield tunnel project of Changsha Metro Line 3 underpass Metro Line 1,the threedimensional model was established using the Midas/GTS NX software.Considering the soil bin pressure,grouting pressure,grouting amount and excavation speed,the influence of new tunnel construction on surface settlement and existing tunnel displacement was explored.The results show that the increase of soil bin pressure will reduce the surface settlemen,and 90%of the vertical deformation is completed in the interval of 3.5 times the tunnel diameter in front and behind of the tunnel working face.Increasing the grouting pressure and grouting amount can reduce the vertical displacement of the existing tunnel,however the control effect of grouting amount on the vertical deformation of the existing tunnel is greater than that of grouting pressure.The grouting pressure and grouting amount in the study section are increased by 1.5 and 0.6 times respectively,the vertical deformation of the existing tunnel is reduced by 0.5 and 0.9 mm respectively.With the increase of shield excavation speed,the greater the disturbance to the stratum,the greater the maximum surface settlement and the maximum vertical displacement of the existing tunnel.The research results can provide technical guidance for the similar engineering construction.