Abstract: In order to study the impact of over pass of a proposed tunnel on the existing transportation lines, the shield tunneling project in the interval from Fuxing Road Station to Beiyanhu Station on the southern extension line of Line No. 4 of Hefei Rail Transit is presented as the case history. The proposed project crosses the existing Line No. 4 from the Science and Technology University Research Institute Station to the Beiyanhu Station. The numerical simulation combined with field measurements are used to investigate the deformation response of the existing transportation lines during the construction of the new tunnel. The results show that the construction of the new shield tunnel will disrupt the existing soil balance, causing the unloading rebound of the soil, thus resulting in the vertical uplift deformation primarily in the existing transportation lines and connection channels. Through the simulation based on the actual operating conditions, it is found that the maximum vertical deformation of the interval tunnel is 2.074mm, and the maximum vertical deformation of the connection channel is 2.075mm. According to the safety control requirements of the existing tunnel structure and the analysis based on the field measurements, both the simulation results and the measured data are below the warning threshold of 3mm, indicating that the existing interval tunnel is in a safe and stable state according to the simulation calculations.

Key words: Shielded Tunneling, Over Pass, Numerical Simulation, Field Measurements Analysis