Abstract: The location, longitudinal profile, mode (doubletrack tunnel tube or twin singletrack tunnel tubes), lining structure, construction organization, and disaster prevention and evacuation of ChongmingTaicang Yangtze river crossing tunnel of ShanghaiChongqingChengdu highspeed railway are studied: (1) The Qiyakou tunnel location is recommended on the basis of analysis on the stability of the riverbed and by means of technical and economic comparisons. (2) A Vshaped longitudinal profile of the tunnel and the principle of controlling the overburden of the river crossing tunnel are proposed on the basis of analyzing the topographical conditions, scouring conditions, geological conditions, and ship anchorage impact of the riverbed. (3) Largediameter doubletrack shield tunnel is proposed after technical and economic comparisons. (4) Composite doublelayer lining structure consisting of prefabricated segment lining and castinsitu concrete lining is proposed on basis of analysis on the impact of the scouring of the riverbed at local areas. (5) Two shield machines are proposed for the construction of the tunnel according to the principle of "environmental protection, controllable risks and dynamic adjustment". (6) Emergency exits, undertrack evacuation passages, and refuge areas are arranged for the tunnel by using the vertical shafts and the space under the track.

Key words: highspeed railway, shield tunnel, rivercrossing tunnel, tunnel design, composite lining