隧道近接施工对上部既有重载铁路隧道安全稳定性影响研究

基于京张高速铁路草帽山隧道下穿唐呼铁路北草帽山隧道工程,探究不同施工方法、不同夹层厚度、不同列车轴重对既有隧道衬砌结构沉降变形、振动加速度和振动速度的影响规律,并结合现场实际监控量测数据进行对比分析。研究结果表明:重载列车激励荷载作用下,下穿隧道采用三台阶法开挖时引起既有隧道的沉降值和振动响应均较小;新建隧道下穿既有重载铁路隧道的最小安全距离约为1.0B,且随着掌子面的不断向前推进,既有隧道沉降值、振动响应幅值均逐渐增大;掌子面距交叉点约30 m范围内,既有隧道沉降值和振动响应受下穿隧道施工影响较大;既有隧道衬砌结构边墙处y方向振动速度最大,z方向次之,x方向振动速度最小;随着列车轴重的增加,振动加速度幅值明显增大。

Impact of Undercrossing Tunnel on Safety and Stability of Existing Heavy-duty Railway Tunnel

In this paper,based on the project of the Hat Mountain Tunnel,a part of the Beijing-Zhangjiakou high speed railway,undercrossing the existing Tangshan-Huhhot heavy-duty railway North Hat Mountain Tunnel,the impact of different excavation methods,different interlayer thickness,different axle loads on the settlement deformation,vibration acceleration and vibration velocity characteristics of the existing tunnel lining was investigated,and a further comparison was made with the field monitoring data.From the results of the study,it can be seen that under the excitation load of heavy-haul train,the settlement value and vibration response amplitude of the existing tunnel are smaller when the undercrossing tunnel is excavated by the three-step method,compared with the full face method and two-step method.The minimum safe distance for a new tunnel undercrossing an existing heavy-duty railway tunnel is approximately 1.0B.As the tunnel face moves forward,the settlement value and vibration response of the existing tunnel both increase gradually.When the tunnel face is within 30 m from the intersection,the undercrossing tunnel excavation has great effect on the settlement value and vibration response amplitude of the existing tunnel.Additionally,the vibration velocity at the side wall of the existing tunnel lining structure in the y direction is the largest,followed by the vibration velocity in the z direction and x direction.As the axle load increases,the amplitude of the vibration acceleration increases significantly.