Wenxiang tunnel for Zheng-Xi Special Passenger Railway has been done a series of research on optimizing the construction method for shallow large-span loess tunnel. According to the field monitoring of ground settlement

vault settlement and primary support stress of the tunnel section before tunnel undercrossing the Lian-Huo expressway. The result indicates that soil settlement and primary support stress can not be controlled very well; and the current construction scheme needs to be reformed since it can not satisfy construction safety requirement. Through synthetical analysis

some optimized methods such as reducing excavation area

increasing excavation steps of pilot tunnel

reserving core soil

quick closure

reinforcing primary support

etc. have been used in construction; and their security and reliability are verified by numerical analysis software fast Lagrangian analysis of continua in 3 dimensions (FLAC3D). From feedback of field implement and monitoring result

the effect of optimized methods is significant; and these methods ensure the undercrossing project implements successfully. These research results have high referential value for analogous project to control soil settlement and protect the safety of neighbouring building facilities