Recently, the Shenzhen Metro Line 13 joint utility tunnel project undertaken by Shanghai Tunnel Engineering Co., Ltd. reached a key milestone. During a 6-day shield tunneling advance, the shield machine in the section from the metro receiving shaft to No. 3 comprehensive shaft successfully passed through the safety protection zone of the operating Metro Line 1 between Shenzhen University Station and Hi-Tech Park Station, achieving a maximum daily advance of 9 rings and an average daily advance of about 7 rings. This crossing marks Shanghai Tunnel Engineering's first close-distance crossing beneath an existing tunnel in composite strata in the Guangzhou-Shenzhen region.

Project Overview 

The Line 13 joint utility tunnel project is one of the joint utility tunnels of Shenzhen's Phase IV rail transit construction. The entire line is co-located with Metro Line 13, with coordinated design and simultaneous construction. The project includes the Nanshan section main trunk utility tunnel and the Shiyan section branch utility tunnel, with a total construction length of 8.1 km, of which the section constructed by the shield method is about 3 km long.

This crossing is the company's first close-distance crossing beneath an existing tunnel in composite strata in the Guangzhou-Shenzhen region, with both risks and challenges, facing:

① Interchanging strata, including hard plastic gravelly clay, strongly weathered granite, and other strata.

② The minimum clear distance from the operating metro is only 1.7 meters; the operating metro tunnel has a long service life and high passenger flow.

③ Ground reinforcement to control settlement is not possible; the ground above the crossing section is an interchange bridge with dense traffic.

With no similar working conditions to reference, how did the project team manage to "pass by each other and remain safe" with Line 1? The answer lies here:

In the early stage, shield tunneling experts from the Guangzhou-Shenzhen region were invited to review the crossing plan, providing professional guidance for the crossing; full communication mechanisms were established with all parties to create favorable conditions for the crossing.

During the shield crossing, 24-hour uninterrupted monitoring was carried out, achieving refined settlement control through multiple means: real-time analysis of muck discharge to precisely control excavation advance; comparison of muck samples with geological reports to analyze stratum changes and apply timely remedies; injection of shield shell filling material during the underpass to strictly control grouting parameters.

In addition, the project team, together with the Chengdun Sui'an emergency maintenance team, mobilized internal and external resources, equipped structural and track professional emergency supplies, and made emergency preparations.

After the shield passed, automatic monitoring data in the Line 1 tunnel showed that the maximum settlement and displacement values did not exceed ±2 mm, far below the 10 mm control value required by the designer, marking the great success of this crossing. It provides valuable empirical parameters for subsequent underpasses of Metro Line 9, Line 2, and Line 13, and accelerates the tunnel breakthrough!