ABSTRACT
F. Zhang & H. Kong Beijing Municipal Engineering Company, Beijing, China
ABSTRACT: According to the design, there should be a connecting tunneling between two shield driven tunnels, the connecting tunnel is often built by NATM in China. In a real project, the geological condition of the ground is typically complex consisting of clayey soil, saturated fine sand, and saturated gravel soil. The soil cover above the crown of connecting tunneling is about 8.0 m, and there are three existing utility pipes passing above the tunnel. Heavy traffic road is directly above the tunnel and there are many old buildings in the same directions as the tunnel center line. Therefore, the construction of this connecting tunnel may take a high risk; moreover, two segments of existing shield-driven tunnels should be removed before this tunnel is dug. Because the location of this connecting tunnel is very sensitive to the surrounding environment, how to construct is a challenge to us, especially, how to remove the two segments is very important in this difficult ground condition. This similar engineering accident has ever appeared in Shanghai. According to the results of numerical simulation, the detailed construction method was constituted to affect the pipelines less and to avoid the large disturbance above the ground, including the remove order of two segments. Besides these, a series of in-situ measurement were carried out during the whole period of construction. After the project was finished, the maximal ground settlement was only 4.1 mm, the whole project was successfully completed without any accident and the surrounding environment was protected very well. At last, the results of numerical simulation were compared with the in-situ measurement, the result indicated that numerical simulation can predict the ground settlement well. It can be said that the experience on this project is valuable to solve similar problems in connecting tunnel between two shield driven tunnels.
