Abstract: The main line of water supply project from Songhua River to the central cities of Jilin province has a total length of 263.45 km, including 133.98 km of tunnel and 129.47 km of Prestressed Concrete Cylinder Pipe (steel pipe and cast-in-situ culvert). Key technical issues of this project are summarized as follows: type of water diversion project, technology of the ultra-long pressure tunnel, selection of TBM(Tunnel Boring Machine), technology of the tunnel across limestone area, technology of underwater rock plug blasting, technology of prestressed reinforced concrete lining, and technology of the prestressed circular culvert (D=5.1m). The practical situation of the project and the technical feasibility are elaborated. The water diversion project is selected as surge-tank type; the pressure tunnel has a length of 97.62 km, and cast-in-situ culvert 2.26 km; the tunnel crosses the limestone area in a straight line; and open TBM construction is adopted. In the light of the characteristics of tunnel's overburden layer, 15 segments of the lining should be designed to resist cracks, and hence prestressed lining is adopted with a total length of 14.756 km. The project is the first in northeast China to cross limestone area with ultra-long pressure tunnel. The investigation and researches will provide technical support for the project.

Key words: type of water diversion project, ultra-long pressure tunnel, selection of TBM, route selection for tunnel across limestone area, rock plug blasting, prestressed concrete lining