The Key Construction Technologies of Embedded and Large Span Tunnel in Soft Flow Mucky Ground

There is a 333.586 m length tunnel for parking and cross-over track at the north Gulou station between Gulou station and Xuanwumen station, which the largest span is 17.358 m. The spacing interval is small, and the smallest is 0. The tunnel has many chambers, and the section area is varied. A 320.6 m length tunnel goes through the soft muddy and silty ground at the south Xuanwumen station. The tunnel crown is located 8 m to 9 m below the ground surface, where there are structures on the ground, pipeline and built-constructions under the tunnel. All the constructions therefore must be secure and steady in the process of excavating. The paper analyzes both the construction difficulty and features of large span and parking cross-over track tunnel in the soft flow mucky ground. The construction method of bench cut method, center diagram method (CD method) and both side drift method are adopted on the base of the theory. Finally the paper introduces the construction scheme and support method in the soft flow mucky ground. From the effect of construction, it is concluded that the construction method and the reinforcement method are right. In a word, the constructions are secure and steady in the whole process of construction.