Abstract: Adaptive design of dualmode shield in waterrich gravelmudstone composited strata is of great significance. As a result, the targeted designs of structure and functional system of slurry/earth pressure dualmode shield used in Wuyi Interchange stationXinxiu Park station on Nanning Rail Transit Line No. 5 are put forward according to the construction risks such as crossing through Yongjiang River, crossing underneath buildings with shollow foundations, surface settlement induced by shield boring in gravelmudstone composited strata, and muck cake on cutterhead. As for structural design, the air cushion chamber is used to stabilize slurry pressure, and the slurry discharge port is optimized so as to realize the stable control of surface settlement. The brush and P0 pump circulation systems are set on central panel and bracket to effectively reduce the mud cake phenomenon. The design of screw conveyor is optimized to reduce the gushing pressure, and compared with the adjacent lines, the boring speed of the rivercrossing section is increased by nearly one time. As for functional system, mucking system conversion between slurry and earth pressure dualmode is realized, the total thrust of the propulsion system reaches 39 910 kN, which can meet relevant requirements under different working conditions, the surface settlement is strictly controlled according to grouting system and rational tunneling parameters control.

Key words: rail transport, tunnel, dualmode shield machine, composited strata, targeted disign, rivercrossing tunnel, cutter and cutterhead