Study On The Design Parameters Of High Slope In Bridge And Tunnel Connecting Section

There have been many bridge and tunnel connecting section connecting section along the proposed ChangKun passenger line when pass through the mountain areas. TThere are no clear relevant railway specifications and manuals for the design form and slope design parameters of bridges and tunnels connecting section in current. In this study? a proposed design form applied for the outlet slope of Xuefengshan1st tunnel and Dayanwan11st tunnel have been created, based on summarizing the design features of bridge and tunnel connecting section and engineering geological conditions of investigated sites. The slope stability and dynamic response of bridge and tunnel slope in different geometric design parameters are analyzed with the help of MIDAS/GTS software.The main research contents and results are as follows:(1) Based on the design features of bridge and tunnel connecting engineering, the outlet slope of Xuefengshan1st tunnel is suitable for the form of butt-connected bridge and tunnel connecting section, and Dayanwan1st tunnel is suitable for the form of connected in series type.(2) The results of static analysis of slope under bridge loads shows that the change of stress in the bottom of the pile is reducing with the increase of depth of the abutment. When the depth of the abutment is more than20m the change of equivalent stress in the bottom of the pile is less than0.1. Whether the bridge loads has an impact on the slope surface, is mainly determined by the position of the abutment in horizontal.(3) From the dynamic analysis of slopes in the two investigated sites, the dynamic response peak acceleration of the bridge and tunnel slope surface under the train dynamic loads is less than0.05g and the peak displacement is less than1mm.(4) The bridge foundation depth should be taken as20m and the distance between outside of the pile cap and the surface of the slope should be5m when the type of bridge and tunnel connecting in the outlet slope of Xuefengshan1st tunnel is butt-connected. The safety excavation slope in longitudinal direction is1:0.75and it should be taken in the way of making a2m wide platform per8m. The desirable slope of side slope in tunnel portal is1:0.25. After the construction, the slope surface of tunnel entrance should be recovered as natural.(5) The tunnel slope is stable in case the length of abutment built-in tunnel ranges from0to10m when the type of bridge and tunnel connecting in the outlet slope of Dayanwan1st tunnel that connected in series. When the length that the abutment built-in tunnel ranges from0to5m, the bridge load has an obvious impact on the stability of tunnel slope and little impact beyond5m. The upper part of both sides of the tunnel entrance is the area where failure most likely to occur...