A Parallel Interchange Tunnel Construction Sequence And The Adjacent Influence Subzone Study

The stratigraphic effect and the mechanical behavior of the structure caused by Stereo cross tunnel constructionis very complicated. The newly built the construction of the tunnel, make the first built around the tunnel wall rock relaxation, especially in the tunnel near the construction, this effect will be more obvious, severe fracture failure of the tunnel structure and the surrounding rock collapse slip shift. Therefore, the reasonable construction method is particularly important. Based on the underwater ultra-shallow section overpass tunnel building technology research topics, and take the east coast of Xiangjiang Tunnel in Changsha Yingpan Road as the background, using the numerical simulation of the research methods, focus on the parallel interchange tunnel construction sequence and the interchange area close construction effect of the partition, the major work completed as follows:(1) The Yingpan Road tunnel east coast parallel the interchange upper C, D, ramp excavation on the lower part of North and South main line of the second disturbance, resulting in the mainline tunnel in which the stress environment changes, affecting mainly the arch of the tunnel.(2) Four construction sequence programs about underground parallel interchange tunnel are provided. And it analyzes the calculation of three-dimensional numerical simulation. After Comprehensive comparison of multiple indicators survey, the best sequence of construction is to excavate the lower part of the tunnel firstly and then excavate the upper tunnel.(3) Obtained the settlement of ground surface, the stress field of interchange site soil and the stress rule of initial support structure under different spacing conditions, and finally it gives approaching construction of division of the four tunnel parallel interchange of Changsha City interchange tunnel underground parallel.(4) When the vertical spacing is larger than4D, it didn’t need to consider the vertical spacing of parallel interchange tunnel close construction influence, can be considered as two parallel tunnels. And when the level spacing is larger than4D, it didn’t need to consider the level spacing of parallel interchange tunnels close construction influence, can be considered as two intersecting tunnels.