Settlement of subway tunnel affected by different pilot tunnel sequences excavation

摘要

Based on the subway tunnel excavation from Beijing Railway Station to Beijing West Railway Station, the study use FLAC-3D software to simulate 9-pilotsexcavation progresses under traditional and simplified sequences. The results of simulation show the changes of crown settlements, surface subsidence and of settlement trough curve. And the excavation sequences have been optimized, based on the geological conditions. The results are drawn as follows: (1) Settlements of crown and surface with simplified sequence are serious. (2) Settlements for traditional sequence grow dramatically. (3) Settlements of optimized sequence are the smallest. (4) The centerlines of settlement trough return to the centerline of tunnel, when transaction excavation is finished. Consequently, shape of settlement trough should be considered to get the largest settlement value, when supports with high elastic modules are used. The results of optimized show this sequence and analysis methods would bring benefits for double side heading method tunneling.