双线盾构近距下穿既有地铁地表位移规律研究

Research on the Ground Displacement Law of Double-track Shield Tunneling under-crossing Existing Metro

研究目的:为明确西安地铁5号线南稍门——文艺路区间隧道盾构下穿既有2号线施工过程中地表位移的规律,采用FLAC3D研究盾构下穿过程中地表沉降与地表水平位移的变化,对比不同工况下的地表沉降及水平位移,从而给出盾构施工的合理参数。研究结论:(1)盾构下穿施工的地表沉降曲线及水平位移均与普通盾构施工有着显著差异,处于既有隧道周围一定范围内土体的地表位移受既有隧道的影响,其沉降及水平位移曲线量值及形状均发生较大改变;(2)随着盾构施工参数(土仓压力与注浆压力)的增大,地表沉降量不断减小,当土仓压力超过0.18 MPa、注浆压力超过0.16 MPa后,调整施工参数已难对地表沉降起到显著效果,最终确定了0.18 MPa(土仓压力)、0.16 MPa(注浆压力)的施工参数建议值;(3)通过现场监测,地表沉降测线上最大沉降量均满足规范要求,表明施工参数建议值对地表沉降起到了较好的控制效果;(4)本研究成果可为其他地铁盾构下穿施工提供参考。

Research purposes:In order to clarify the law of ground displacement during the construction process of tunnel shield between Nanshaomen and Wenyilu of Xi′an Metro Line 5 undercrossing the existing Line 2,this paper used FLAC3 D to study the changes of ground settlement and ground horizontal displacement in the process of shield underpass,compared the ground settlement under different working conditions,and gave the reasonable parameters of shield construction.Research conclusions:(1)The surface settlement curve and horizontal displacement of the shield tunneling under-crossing are significantly different from those of the ordinary shield tunneling.The surface displacement of the soil around the existing tunnel is affected by the existing tunnel,and the value and shape of the settlement and horizontal displacement curve are greatly changed.(2)With the increase of the shield construction parameters(chamber pressure and grouting pressure),the ground settlement is decreasing continuously.When the chamber pressure exceeds 0.18 MPa and the grouting pressure exceeds 0.16 MPa,it is difficult to adjust the construction parameters to have a significant effect on the surface settlement.Finally,the recommended construction parameters of 0.18 MPa(chamber pressure)and 0.16 MPa(grouting pressure)are determined.(3)Through on-site monitoring,the maximum settlement on the surface settlement measuring line is within the requirements of the specification,indicating the suggested construction parameters has a good control effect on the surface subsidence.(4)The research results can provide references for the construction of other metro shield under-crossing projects.