| NATM (New Australia Tunnel Method) is a widely used method in the course of building metro tunnels. Though there are many successful examples in building connecting tunnel at home and abroad, but the double connecting tunnel of BaiXue internal tunnel has the trait of big span, frequently changed sections, complex structure, marked effect of multi-tunneling, and approaching to the land surface, which is The South Street of ZhongGuanCun with busyness traffic. So the construction of the connecting tunnel is important technical difficulty. We made a new construction scheme which about orders and methods of the excavation. In this paper, the construction processes of connecting tunnel are simulated by means of FLAC3D program. Thus land subsidence values and its regularities of distribution are forecasted. The distribution of plastic zone and weak link during construction are also analyzed. By means of numerical simulation, the optimized construction plan of connecting tunnel is reasonable and feasible in theory is proved. In the construction processes of connecting tunnel, we made a strict plan to monitor land subsidence, earth pressure, reinforcement force and collected abundance monitored data. Based on both of numerical simulation and the monitored data of excavation, it is proved to be safe that the max land subsidence reached 50mm. The paper' s conclusion can be used in similar engineering.
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