Recently, the “Stefanie” shield for the northeastern extension line of Singapore metro, undertaken by China Construction (Singapore) Co., Ltd. and China Construction Tunnel Corp., Ltd. was successfully launched. The project is the first overseas metro project of China State Construction using an independently developed metro shield and is a significant step for going global in infrastructure construction, according to the Belt and Road Initiative.
The double-track length of the tunnel of the northeastern extension line of Singapore metro is 1.6km, and the double-track length of the shield interval is 1.4km. Two major shield tunneling machines used in the project were developed and manufactured independently by China, with an excavation diameter of 6.67m. The shield interval passes underneath Punggol Waterway; the minimum clearance between the bottom of the Waterway and the tunnel is 6.169m, with complex geological and hydrological conditions and substantial risk. In addition, the launching shaft of the project is 28.4m in length, and the overall length of the shield tunneling machine is up to 100m. Given the long construction period, narrow site, and the insufficient launching space of the open-cut tunnel, the split launching scheme is used to substitute the conventional integrated launching, which involves more technical difficulties.