Numerical Analysis For Secondary-lining Of Subway Station Tunneled In Center Drift Method

Based on center diagram method and center cross diagram method, Center drift excavation method is developed as a new construction method for the large-scale shallow tunnel engineering after side drift excavation method and PBA method. Compared with traditional shallow tunnel construction method, Center drift excavation method can control the surface settlement in construction and meet the requirement of city environment safety and as well as have dominant technology, which is base on lower economic condition. However in practice it is found that the construction time slot between initial lining and second lining for center drift excavation method is less than for traditional shallow tunnel construction method, so second lining will take on the weight of surrounding rock before the distortion of initial lining have finished. At the same time when the side drift is excavated, the load on the second lining will change again and accordingly the internal force and the distortion of second lining will also adjust itself, therefore it is necessary for center drift excavation method to make thorough research.So in this paper, based on the above facts and several typical stations constructed by center drift excavation method on Beijing metro line 5, the mechanics characteristics of the second lining of station under construction were studied to achieve the worst load. The calculational process and the structural design for the metro station constructed by center drift excavation method were optimized. The generic flow of structural analysis and more rational transect shape of subway station were achieved.