Research On Construction Technology Of Large Section Tunnel Crossing Under The Existing Subway Tunnel By Means Of Shallow Tunneling Method

With large section, shallow overburden, the subway station tunneling under a running Metro proves to be very complicated engineering. The upper existing tunnel demands that the construction of the subway station have to focus on its displacement so as to ascertain the normal running and prevent it from damage caused by settlement of soil mass. A systematic controlling process consisting of exploring, forecasting, monitoring and engineering measures was put forward, in which the total subsidence was divided into every step of the construction. Through controlling the value of settlement caused by its corresponding step, the total settlement standard could be reached.The dissertation includes four main technical problems confronted in crossing tunneling: the displacement style and possible damaging model, construction method, the working principle of long level steel pipe and the construction administration controlling method.The details are as follows:1. Based on the measuring data of the running tunnel during construction, the displacement law was summarized and the diagrams was drawn. Several kinds of possible damaging styles of the existing tunnel was analyzed by means of mechanics models.2. A number of construction method in view of large-section tunnel were researched. The characteristics of environment effects were compared. Further analyses were made on key construction steps of the method that would be adopt.3. The beam model on elastic foundation was used to simulate the behavior of long level steel pipe during excavation on basis of considering all construction contents in detail. The equations expressing the relation between factors were founded. At last a designing method of long level steel pipe based on deflection controlling was put forward.4. The displacement-dividing principle was founded, which associated the construction steps of metro station with the settlement control of the existing subway tunnel tightly and easily operated.The proceeding research work basically made clear the main aspects confronted in crossing tunneling engineering and corresponding measures.