CCCC Third Harbor Engineering's Intelligent Dual-Mode Shield Machine Sets Record of 5 Rings Per Day on Guangzhou Metro in China

en.Wedoany.com Reported - CCCC Third Harbor Engineering achieved a construction performance of up to 5 rings per day with two intelligent dual-mode shield machines on the Jiaofeng section of the Guangzhou Metro Line 8 North Extension project, with efficiency exceeding the average level of similar stratum construction, and achieving zero accidents and zero settlement throughout the entire process. The tunnel has a burial depth of 30 meters, with a karst cave encounter rate of 92% in the area. The fluid-plastic water-rich sand layer and hard limestone are interbedded, with uneven soft and hard strata accounting for over 20%. The upper part of the tunnel consists of a highly unstable water-rich sand layer, while the lower limestone has hardness far exceeding ordinary concrete. The geological conditions are regarded by the industry as a "forbidden zone" for shield construction.

Traditional shield construction mainly adopts two single modes: earth pressure balance (EPB) or slurry. The project team's analysis found that the EPB mode is prone to soil blowout and face instability in water-rich sand layers, while the slurry mode has low excavation efficiency and high construction costs in hard rock sections. Neither mode could adapt to the geological conditions of the Jiaofeng section.

To address this, based on complete detailed geological surveys and supplementary exploration data, combined with numerical simulation excavation tests and construction experience in similar strata, the project team developed a complete set of "EPB/slurry dual-mode shield + comprehensive regulation" construction technology after six months of research, demonstration, and scheme optimization in early 2025. They also customized intelligent dual-mode shield machines in collaboration with equipment manufacturers.

The dual-mode shield machine is equipped with a dual-channel system for "direct slurry discharge + screw conveyor mucking" and features a standardized mode conversion process. During construction, the shield machine can sense stratum changes in real time and autonomously switch modes: when encountering water-rich sand layers and karst caves, it switches to slurry circulation mode, stabilizing the tunnel face with stable slurry pressure and quickly discharging slurry; when entering clay or hard rock sections, it switches to EPB mode, efficiently discharging muck through the screw conveyor, solving the problems of material clogging and mud cake formation common in traditional equipment.

The shield machine is equipped with a high-precision advanced geological detection system, using cutterhead rock-breaking vibrations and reflected wave imaging technology to perform real-time scanning of the stratum 100 meters ahead, identifying hazards such as karst caves, fracture zones, and water-rich areas. The team also built a triple detection system of "advanced prediction inside the tunnel + cross-hole CT verification on the ground + periodic review with geological radar," and adopted quincunx hole layout and sleeve valve pipe grouting technology to comprehensively reinforce the weak stratum within a 2-meter range outside the tunnel perimeter.

Currently, the two intelligent dual-mode shield machines have cumulatively advanced over 798 meters, and the tunnel construction progress is gradually becoming clear. The complete set of complex geological shield construction solutions summarized from the project has accumulated replicable management experience for subsequent construction in similar strata.