Abstract: In this study, the characteristics of a horseshoeshaped segment of the Baicheng tunnel of the Menghua railway are analyzed to realize the efficient segment assembly of a horseshoeshaped shield tunnel by simulating the segment assembling process. In addition, a hybrid configuration with decoupling of position and attitude is proposed, and a novel mechanical locking device with double hoisting bolts is designed. Through analysis of mechanical principle, the flexibility of the end mechanism is improved using the redundant drive finetuning mechanism. Moreover, a fine adjustment angle ± 14° is realized, and a segment erector with six freedom degrees and seven activity degrees at the end is developed to overcome the problem that the normal line at the connection surface of the segment does not pass the rotation center of the erector. The findings show that the shield tunneling method is suitable for horseshoeshaped tunnels, and the segment forming quality and construction efficiency can meet the engineering requirements, ensuring the smooth penetration of the tunnel. 

Key words: tunnels, horseshoeshaped shield, segment erector, multiple freedom degrees