Analysis Of The Influence Of The Excavation Of Super Deep And Large Foundation Pit On Adjacent Existing Metro Tunnels

With the development of urbanization in China, there are a growing number of constructions of subway and deep excavations. Due to the shortage of land in city, it inevitably leads to the emergency of deep excavations excavated adjacent to metro tunnels. Deep excavation adjacent to metro tunnels would cause many adverse effects. The metro tunnels are strict in settlement and deformation, whether the method of excavation is suitable or not, it would directly affect the safety of tunnels.The paper based on the construction of National Finance Information Building, with the use of Midas GTS software modeling the progress of excavation, the influence of excavation on the adjacent tunnels have been researched. The related work and results are as follows:(1) To provide the experience and reference for the study, some papers have been read to know about the present research status at home and abroad.(2) The theories of estimation of deformation caused by deep excavation have been presented to make a reference to the numerical modeling.(3) With the use of Midas GTS software modeling the different methods of excavation, the influences on the adjacent tunnels have been studied. Due to the3D Finite Element analysis of deep excavations, we found that basin excavation is more suitable than island excavation, the method of basin excavation can effectively control the deformation and displacement of adjacent tunnels. The modeling of excavations with different distances between tunnels and deep excavation has been conducted to study the influence on tunnels caused by deep excavation. With the distance between tunnel and foundation pit increasing, the influence caused by deep excavation becomes smaller. With the modeling of deep excavation supported by different thickness of diaphragm wall, the influence on the tunnel has been studied. We found that the optimum thickness is800mm.(4) According to the features of the influence on the tunnels caused by deep excavation, two measures have been proposed. They are monitoring scheme and reinforcement measures.