The Safety Analysis When The Newly Subway Shield Tunnel Is Crossing The Existing Railway Turnout

Along with the rapid construction of the subways, the subway construction has been spread to the surburbs; the crossing projects of the new subway tunnel crossing railway track or railway turnout area are confronted more and more. The turnout is the one of the three weak links of the track structure. Moreover, the railway transport is particularly busy and regular operating of trains and zero track settlement are demanded by the railway department in many crossing projects.In this paper, supported by the crossing project of the shield driven tunnel of Fengtai East Road to Fengtai South Street in No.9 line of Beijing subway shield beneath the Fengtai railway station, the finite element analysis software ABAQUS was used to establish the static 3-D finite element model of the turnout-Double subway Tunnel. The Influence of different excavation methods of the shield tunnel to the safety of turnout structure was studied, the evaluation indexes involved are the deformation of turnout structure and turnout static geometry, including turnout settlement, rail lateral displacement, longitudinal level, track cross level, track twist, track alignment and track gauge. The analysis of the influence above was made on the following aspects:(1) As for the left line of the shield tunnel excavation, the change of turnout geometry were analyzed to obtain the curve of the change of turnout geometry due to the left line tunnel excavation; (2) For the turnout is asymmetric, the left and right line of the tunnel excavation turnout caused by changes in turnout geometry were compared; (3) As the right line of the shield tunnel was excavated on the basis of the left line of the shield tunnel excavation, the influence of secondary disturbances of soil to the turnout geometry was investigated; (4) The influence of simultaneous excavation of Double subway tunnel on turnout geometry was also studied; (5) The security control measures of shield tunnel crossing the turnout structure were summarized and the effectiveness of pre-reinforcing the foundation, trengthening of turnout with I iron track-locking and changing the intensity of the grouting, to enhance the impact of the turnout geometry was verified.