盾构下穿对既有隧道影响的模型试验研究

Model Test Study on Influence of the Undercrossing Shield Tunnel on the Existing Tunnel

盾构隧道下穿施工对既有地下结构周围的土体产生二次扰动,会改变既有隧道原有的受力状态以及内力分布,给既有隧道的正常运营带来不利影响。针对此问题,本文采用北京工业大学研制的盾构机,开展了大尺寸盾构隧道开挖模型试验,真实地模拟了隧道的开挖过程,研究了盾构开挖对既有隧道内力的影响。试验结果表明:下穿过程中,沿既有隧道纵向的应力表现为上压下拉;弯矩的最大值出现在既有隧道的中心断面处,且在刀盘位于既有隧道正下方时增长最为迅速。因此,对于下穿施工,应当重点关注穿越阶段既有隧道近开挖处的内力,防止出现结构破坏。

The undercrossing of the shield tunnel will cause secondary disturbance to the soil around the existing tunnel,which will change the existing tunnel’s original stress state and internal force distribution.This will adversely affect the normal operation of the existing tunnel.In this paper,the shield tunnelling machine designed by Beijing University of Technology is used to carry out a large-scale shield tunnel excavation model test,and the influence of undercrossing on the internal force of the existing tunnel is studied.The test results show that during the undercrossing process,the stress along the longitudinal direction of the existing tunnel is compressive at the top and tensile at the bottom.The maximum value of the bending moment appears at the central section of the existing tunnel,and its growth is the fastest when the cutter head is right below the existing tunnel.Therefore,for the undercrossing construction,the internal force of the existing tunnel near the excavation zone during the crossing stage must be focused on to prevent structural damage.