盾构下穿既有隧道施工加固方案优化研究

Study on optimization of construction reinforcement schemes for shield undercrossing existing tunnels

针对盾构下穿施工使既有隧道产生较大沉降的问题,以北京新建地铁14号线下穿既有15号线的隧道施工工程为背景,进行盾构下穿既有隧道施工的加固方案及其参数优化研究.首先,采用有限元软件Midas GTS NX建立盾构下穿既有隧道施工的动态掘进模型,对加固既有隧道、加固夹层土、加固新建隧道3种加固方法的模型分别进行计算分析;然后,通过对比分析确定较优加固方案,并利用现场实测数据验证数值模型和计算结果的可靠性;最后,以沉降为指标研究方案的参数(加固体角度、加固体厚度、加固体长度)对加固效果的影响,最终确定优选加固方案.研究结果表明:加固新建隧道对地表沉降和既有隧道变形的控制效果明显优于加固既有隧道、加固夹层土两种方案;采用加固新建隧道措施时,加固体沿隧道的环向加固范围为270°、隧道平面交叉外的加固长度L为10 m、径向加固厚度为2 m时变形控制效果较好.研究成果可以为类似盾构下穿施工工程提供参考.

Addressing the issue of substantial settlement in existing tunnels caused by shield tunneling,this study focuses on the optimization of reinforcement schemes and parameters for shield undercross-ing existing tunnels,based on the Beijing new subway Line 14 project,which involves the undercross-ing of Line 15.Firstly,a dynamic excavation model for shield undercrossing existing tunnels is con-structed using the finite element software Midas GTS NX.This model is used to calculate and analyze three reinforcement methods:reinforcing the existing tunnel,reinforcing the interlayer soil,and rein forcing the new tunnel.Subsequently,the optimal reinforcement scheme is determined through com parative analysis,and the reliability of numerical models and calculation results is validated using the field-measured data.Finally,considering settlement as a primary criterion,the study investigates the influence of parameters(reinforcement angle,thickness,and length)on the reinforcement's effective-ness,ultimately defining the optimal reinforcement scheme.The results show that reinforcing the new tunnel significantly outperforms the other two methods(That is to strengthen the existing tunnel and reinforce the sandwich soil)in controlling surface settlement and existing tunnel deformation.Particu-larly,when adopting the reinforcement of the new tunnel,the deformation control is most effective when the reinforced body extends over a circumferential range of 270°along the tunnel,the reinforce-ment length outside the tunnel plane intersection is 10 meters,and the radial reinforcement thickness is 2 meters.The research provides valuable insights for similar shield tunneling construction projects.