Abstract: In shielddriven Metro tunnels, the shaft mouth is large. In plane connection survey, the method of connection triangle orientation is adopted and the connection triangle can be optimized easily. The accuracy assessment and survey case analysis demonstrate that the method of connection triangle orientation can meet the precision requirements of Metro tunnels both in theory and in practice. Where the shaft is deep and the connection triangle can be arranged, the method of connection triangle orientation can be adopted as the preferred method in the plane connection survey of shielddriven tunnels.

Key words: shielddriven Metro tunnel, plane connection survey, connection triangle orientation, standard error, accuracy assessment