Study On Ground Surface Settlement Due To Tunnel Construction In Chengdu Metro

Shield tunneling is considered as one of the most important methods in the tunnel construction of Chengdu, which will disturb ambient rock mass inevitably, and the ground surface settlement is likely to influence the buildings and the existing pipelines. When the settlement gets to some extent, it will affect the safety of buildings overground and the normal utilization of pipelines underground. To reduce the damages to the buildings overground and facilities underground, which are induced by tunnel construction, it is essential to study the ground surface settlement. By applying FLAC3D numerical simulation, this paper mainly discusses the ground settlement caused by shield tunneling in terms of the particular geological condition in Chengdu, while taking the blocks between Tong Zilin Stop and Southern Train Station as background. And influences on the ground settlement due to buried depth of tunnel, grouting at the tail of the shield, tunneling pressure, the distance between double track tunnels and two-lane tunnel different shield excavation program are also studied. Besides, the application of Grey Theory in forecasting the ground surface settlement of a certain spot in different moments is introduced.The research shows that under the same shield excavating situation, the ground settlement of this shielding section increases as the the covering earth thickens; the strength of tunneling pressure bears relatively big impacts on the ground settlement; the elastic modulus of injected layer influences the ground settlement a lot; under the same excavating condition, the shorter the midline distance, the bigger the ground settlement; and when the former is longer than 16m, its effects on the latter level off; using the two-hole shield tunneling, the plan when holes on the both sides tunneling in the mean time benefits more in controlling the ground settlement than that of doing it one by one; and the application of Grey Theory in forecasting the ground surface settlement in a certain spot at different time is feasible.