Study on Passive Instability Particle Flow Simulation of Tunnel Face in the Shield Tunnel Perpendicular Undercrossing the Sewage Interception Pipe
The construction conditions of earth pressure balanced shield perpendicular undercrossing the existing sewage interception pipe in sandy soil stratum are studied,so as to solve the problem of passive instability of tunnel face caused by excessive support pressure.Taking the section of Shenyang Metro Line 3 undercrossing the existing sewage interception pipe section as the background,a numerical model is established using the particle flow code to study the passive failure modes of the tunnel face,the change of the support pressure and the distribution of the ground stress under the presence of the existing sewage interception pipe.Additionally,the study examines the impact of the vertical clearance between the pipe and the tunnel,as well as the friction coefficient,on the limit support pressure.The failure mode and limit support pressure of the tunnel face are affected by the shield excavation location,and the pipe has the greatest influence on the failure mode when the tunnel face is located 1.0D in front of the pipe.Before the shield crosses the pipeline,there is an increase in stress in the soil layer below the pipeline.The limit support pressure increases with the increase of the vertical clearance between the pipe and the tunnel and the friction coefficient of the particles.When the shield is close to,but does not cross the sewage interception pipe,the pipeline has a significant effect on the passive instability mechanism of the tunnel face.
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