Study On The Control Standards And Measures For Ground Settlement Of Excavated Tunnels With Large Diameter Underpassing National Rail Station

Urbanization promoted rapidly growth of the urban railway transit system, all kinds ofcomplicated situation of engineering construction repetitively arised. One of this condition issubway tunnels crossover the existing railway station yard. In this circumstance, it requestindependence between subway construction and railway operation, which is extremelydifficult. Aiming at the ground settlement caused by Xi’an metro line4Railway stationstation down-traversing Xi’an railway station yard, the paper analyzes the influence to railtrack from the down-traversing of excavated tunnel, the influence include tunneldown-traversing construction to the safety work of the train, to the irregularity of the rail track,to the railway roadbeds and tracks, put forward that the controlling of rail track deformationis the fundament of settlement control when tunnel crossing under the existing railway, theundercrossing construction make large influence to the settlement of rail track, make littleinfluence to the horizontal deflection of the track and deviation of rail direction. The papercombine the vertical deviation controlling value of existing rail track with settlement law ofthe rail track, proposed the maximum settlement controlling value and maximum rate ofsettlement controlling value which content the stipulation of 《Railway Line Repair Rules》and suit this project.According to the experience of Xi’an metro engineering, the paper formulatesconstruction methods and supporting measures of the excavated tunnel which isdown-traversing the railway station yard, include construction methods and supportingmeasures of two sections which is excavated by “CRD” method and double side drift method,research the reasonable thickness of grading circle outside the tunnel contour line by means ofMIDAS/GTS finite element software. The paper make sure that the most excellent andeconomical thickness of grading circle is2.0meter on the premise of meeting the maximumsettlement controlling value and maximum rate of settlement controlling value.Meanwhile, series protective measures when the tunnel is down-traversing the railway stationyard is proposed, including particular construction measures, preventive measures beforeundercrossing and cooperation work with the railway interests.Aiming at Xi’an metro4line project, the paper establish monitoring measurement oftunnel deformation and ground settlement while the excavated tunnel down-traverse therailway station yard, in addition, monitoring measurement to the rail track in station yard isproposed. The result of research will be applied, tested and perfected in the build of Xi’an metroline4.