Influence Zoning Analysis Of Shield Tunneling On Adjacent Building And Its Numerical Simulation

There are various construction methods of urban metro,among which the shield tunneling is the most popular for its most advantageous merit is that it can reduce ground disturbance.However,such disturbance shall not be overlooked.In view of this,the study of the impact of shield tunneling of the adjacent building on ground surface and buildings implies great significance.This paper takes Ling Road ~ Dong Yi Huan Road Section of Line 2 of Hefei rail transportation system as the study background and adopts finite element software to establish numerical analysis model of adjacent construction of shield tunnels.With this model,the following studies were conducted: influence on ground settlement with homogeneous and heterogeneous equivalent circle zones,and in different double-track tunneling sequence;influence zoning of shield tunneling construction approaching neighboring buildings;influence on settlement of adjacent buildings with different double-track tunneling sequence and various soil constitutive parameters.According to the results of model analysis,conclusions are drawn as follows:(1)Upon completion of the left track of shield tunnel,maximum ground settlement occurs right above the left track while ground surface settlement at both sides decreases gradually and forms a symmetric settlement trough.Secondary disturbance on ground is aroused when the right track is completed.The settlement right above the left track continues to increase.The ground near the right track exhibits larger settlement with maximum settlement occurring right above the right track.Not considering the settlement along the left track,settlement along the right track also fits the settlement trough.Upon completion of both tracks,due to a secondary disturbance in the formation,maximum ground settlement occurs at right above the center line between the two tracks.(2)When simulating shield tail grouting with equivalent circle zone,application of homogeneous or heterogeneous equivalent circle zone exerts a certain effect on the results.As simulated settlement with heterogeneous equivalent circle zone is larger than that with homogeneous equivalent circle zone.As the heterogeneous equivalent circle zone is approximate to the reality,simulation results with homogeneous equivalent circle zone shall be magnified accordingly.Moreover,simulation results indicate that buildings impose an impact on ground settlement and tunneling sequence of double-track tunnel imposes an impact on simulation results.Simultaneous tunneling of double-track tunnel causesminimum ground settlement(excluding ground surface near the buildings)while tunneling from the nearer buildings to the farther buildings causes minimum building settlement.(3)The study and analysis of the simulation results verified the validity of the improved zoning influence of shield tunneling.(4)When the shield tunneling is conducted near the buildings,tunneling from the neighboring buildings ca.n reduce the maximum building settlement.Both tunneling sequences almost exert no impact on the building leaning.During the construction of shield tunnels in adjacent buildings,change of soil frictional angle and cohesion can significantly affect the building settlement.