China's First 75-Meter Shield Tunneling Helium-Nitrogen-Oxygen Ternary Mixed Gas Two-Stage Decompression Manned Test Successfully Completed
Deep Collaboration Among CDSA Committee Member Units Fills Industry Gap
December 12, 2025, Guangzhou – China's first manned 0.75MPa shield tunneling helium-nitrogen-oxygen ternary mixed gas two-stage decompression test was successfully completed at the Guangzhou Diving School. This training and test operation was undertaken by China Diving & Salvage Association (CDSA) member unit Sichuan Baodunsui Hyperbaric Technical Service Co., Ltd., with joint organization by the Guangzhou Diving School and Shenzhen DIV Diving Engineering Co., Ltd. The three member units of the Municipal Engineering Diving & Shield Tunneling Hyperbaric Operations Professional Committee collaborated effectively to successfully accomplish this experimental task.
To prepare for practical shield tunneling hyperbaric operations and validate the work and decompression protocols for durations of 20 and 40 minutes under 0.75MPa high pressure, Sichuan Baodunsui actively reached out to relevant member units of the Professional Committee. Building upon their existing collaboration in standards development, they deepened their cooperation to organize intensive manned depth training for 22 selected hyperbaric (shield tunneling) operators and related personnel from Sichuan Baodunsui. This effort resulted in the successful completion of multiple-chamber, full-process manned tests using helium-nitrogen-oxygen ternary mixed gas with two-stage decompression at 0.75MPa. The tests successfully verified the pre-defined operational and decompression plans. The participating team underwent an 8-day targeted training program, further enhancing teamwork across all positions and optimizing operational procedures, thereby laying a solid foundation for future deep-depth shield tunneling hyperbaric operations.
On December 10, Sichuan Baodunsui also invited relevant industry leaders and experts to observe the proceedings and organized a technical exchange seminar. This observation session attracted over 30 top experts and scholars from fields including shield tunneling engineering, hyperbaric technology, and diving medicine across China, who collectively witnessed this significant technological breakthrough in China's underground engineering safety operations. The successful validation of this technology is set to fundamentally transform the safety landscape for pressurized interventions in deep-buried shield tunneling construction in China, providing crucial technical support for the construction of ultra-deep tunnels.
The successful execution of this deep-depth manned test and the observation session exemplifies the extended professional leadership of the CDSA and serves as a model of deep industry-academia-research-application integration among member units of the Municipal Engineering Diving & Shield Tunneling Hyperbaric Operations Professional Committee. It not only marks a major breakthrough in China's shield tunneling pressurized intervention technology but also showcases the platform role of the Professional Committee. With the promotion and application of the 0.75MPa helium-nitrogen-oxygen ternary mixed gas two-stage decompression technology, China's ultra-deep tunnel construction is set to enter a new era characterized by enhanced safety and efficiency. This technological innovation will undoubtedly provide robust technical support for "Chinese Tunnels" going global, injecting fresh momentum into the high-quality development of China's infrastructure construction.
