China National Petroleum’s first undersea shield tunneling project in Yantai, Shandong Province, enters a phase of accelerated tunneling progress

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The first submarine shield tunnel project carried out by China National Petroleum Corporation, and constructed by the Pipeline Bureau Construction Company – namely the shield tunnel section of the LNG transmission pipeline in the West Port Area of Yantai Port – has advanced by over 331 meters since trial tunneling began in mid-June. As of July 28, 268 segments of the tunnel have been assembled, and the formed tunnel appears to be in good condition; all parameters meet the requirements set by design standards. The project is now entering a phase of accelerated progress. The shield tunnel section in question is located in Dajijiagang Town, the development zone of Yantai City, Shandong Province. Employees from the construction company operated state-of-the-art slurry-pressure balanced shield machines to dig through the seabed in the Bohai Sea area of the West Port Area. At a depth of more than 20 meters beneath the surface, they penetrated through complex geological layers such as medium-grained sand, silty clay, silt, and gravelly sand, in order to build a shield tunnel with an inner diameter of 3.08 meters. Once completed, a high-pressure pipeline with a diameter of 1219 millimeters will be laid within this tunnel, serving to transport natural gas from the LNG receiving station to the landmass; it will thus play a crucial role as a vital link between these two areas. To ensure effective risk control during shield tunneling, the construction company carried out a customized modification of the shield machine, equipping it with a special soft soil cutter head that, combined with alloy cutters arranged in a gradient pattern, forms a \"super-hard dragon tooth matrix\". The shield tunneling project for the offshore section of the LNG long-distance pipeline in the Xigang District is located in Dajijia Town, the Development Zone of Yantai City, Shandong Province. Employees from the construction company operated state-of-the-art slurry-pressure balanced shield machines to dig tunnels through the waters of the Bohai Sea in this area. At a depth of over 20 meters beneath the surface, they passed through complex geological layers such as medium-grained sand, silty clay, silt, and gravelly sand, in order to construct a shield tunnel with an inner diameter of 3.08 meters. Once completed, a high-pressure pipeline with a diameter of 1219 millimeters will be laid within this tunnel; it will serve to transport natural gas from the LNG receiving station to the landmass, acting as a crucial link between the two areas. To ensure effective risk control during shield tunneling, the construction company carried out a customized modification of the shield machine, equipping it with a special soft soil cutter head that, combined with alloy cutters arranged in a gradient pattern, forms a \"super-hard dragon tooth matrix\". During the trial tunneling of the shield machine, the shield operator strictly controls the tunneling parameters and the quality of segment assembly to ensure stable posture of the shield machine. The operators also make use of advanced construction technologies and digital twin systems to transmit information such as the shield machine’s posture, geological data, and segment assembly in real time to the visualization platform at the ground command center. This enables remote supervisors to keep track of the shield machine’s operation status in real time, accurately assess any changes in risks, and achieve comprehensive monitoring and control. During the process of sealing the starting tunnel entrance, the technicians took into account the actual geological conditions related to slag discharge and, by relying on their own technical expertise, modified the grouting equipment used for this purpose. By assessing the effectiveness of the grouting during the sealing process, they ensured the successful completion of the sealing work at the starting tunnel entrance.