Abstract: An existing tunnel beneath Terminal 2 building reserved for the Taoyuan International Airport Link Metro Project was enlarged to accommodate the new alignment of Metro rail. The enlargement works were located in boulder formation with ground water head greater than 11.0 meter. The width of enlargement structure varies from 4 m to 18.4 m, and the total excavation volume is 7 927 m3. New thundering earthing system, reinforced strut frames for existing structures and monitoring system were installed to insure the safety and operation of Terminal 2 building. Ground water draw down, double parker grouting and flooding gate erection were performed prior the diamond wire saw demolishment of existing structures. Shotcreting, selfdrilled rockbolt and struts were the main components of the temporary support for excavation faces. This paper describes the details of construction works and the experience gained from this project.

Key words: Taoyuan MRT Airport Line, gravel layer, enlarged excavation tunnel, horizontal dewatering, NATM