Abstract
The open-cut work of Fukudai Tunnel is one of the few cases for its neighboring construction and large-scale excavation (width=about 45 meters, depth= about 10 to 20 meters), and the work was carried out up to approximately 5 to 8 meters vertically above the common utility duct of Fukuoka Outer Beltway and Fukuoka City Subway Line 3 Tunnel, which were both constructed by small diameter NATM method.
Especially, ensuring safety for tunnel structure and railway track were the important issues, since the commencement day of services of Fukuoka City Subway had been scheduled during the construction work of Fukudai Tunnel. On the other hand, behavior of ground and mountain tunnel, in case of open-cut work being carried out right above the existing mountain tunnel, has been indefinite and prediction method of impact has not been established.
The purpose of this paper, using the FEM analysis, is to predict the safety, in advance, to inspect the result of construction test, to clarify the behavior of existing mountain tunnel while open-cut work is being carried out right above itself and to propose the impact prediction method focusing on the deformation modulus and join conditions between the tunnel lining and the ground.
