Right-Line Shield Tunneling Launched on the Shenzhen Metro Line 20 Phase II Project Undertaken by The Sixth Engineering (Xiamen) Co., Ltd. of CCCC Third Harbor Engineering Co., Ltd.

On October 23, the right-line shield of the section from Shenzhen University Station to Hi-tech Park Station of the Shenzhen Metro Line 20 Phase II Project undertaken by The Sixth Engineering (Xiamen) Co., Ltd. of CCCC Third Harbor Engineering Co., Ltd. was launched, marking that the project has officially entered the twin-line tunneling stage; the construction of the section is being accelerated, laying a solid foundation for the subsequent breakthrough of the section and the on-schedule progress of the whole line.

The right line of the section is 506 metres long in total, and an earth-pressure-balance shield machine with an excavation diameter of 6.48 metres is used. It is launched from the small-mileage end of Shenzhen University Station, bores from west to east along Shennan Avenue, and is received at the large-mileage end of Hi-tech Park Station. The launch position has a burial depth of 35 metres; the strata are mainly completely weathered and strongly weathered granite, the geological conditions are complex, and the construction challenges are great. The section adopts a steel-sleeve launch technique, and sleeve sealing, structural reinforcement and control of segment uplift are the key control points under high-pressure working conditions.

To ensure the safety of the launch, the project team strictly controlled the whole process of steel-sleeve construction and carried out sealing, bolt and weld inspections item by item. It innovatively adopted bentonite grouting for pressure retention in place of air pressure retention, and, combined with measures such as H-section steel limiting, bagged-cement counterweighting, “7”-shaped plate restraint and repeated re-tightening of bolts, effectively curbed the risk of segment uplift.

Throughout the construction, the project adhered to the concept of “safety first, quality first”, implemented on-site supervision, strengthened real-time monitoring, and carried out 24-hour dynamic control of surface settlement, pipeline displacement and shield attitude. The technical team optimized the tunneling parameters, fully equipped synchronous grouting, improved the attitude-correction contingency plan, and strictly controlled the quality of segment assembly ring by ring, running standardized construction through the whole shield tunneling process and strictly holding the bottom line of safety and quality.

Faced with challenges such as a tight schedule, many external constraints, a small site and intensive cross operations, the project team kept a close eye on the milestone goals and coordinated the preliminary preparatory work such as scheme demonstration, equipment acceptance and on-site condition verification. All departments worked in close coordination and advanced efficiently, ensuring that the shield launch milestone was achieved on schedule through refined management.

The shield launch is an important turning point in the construction of the section. The project department will continue to consolidate responsibility for production safety, steadily advance shield tunneling, routinely do a good job in risk pre-judgement and emergency response, strictly guard the quality gate, scientifically coordinate the construction schedule, maintain its drive to tackle difficulties, and make every effort to ensure the smooth and orderly construction of the project.