At 7:18 on August 20, as the last cutterhead was split in two, the first shell abandonment and disassembly of a shield machine inside an undersea tunnel at a depth of 60 meters below sea level—currently the deepest cross-sea metro tunnel in China—was successfully completed for the Xiamen Metro Line 3 cross-sea section, creating a miracle of completing 'in-tunnel shield machine shell abandonment and disassembly' in 30 days.
　　Since July 13, when the slurry shield on the right line of the cross-sea section was first driven to the construction method handover point, and operations were carried out in waters more than 60 meters below sea level, with cutter replacement under unsaturated air pressure at up to 5.38 standard atmospheres, setting the latest domestic record for cross-sea slurry shield tunneling, another new domestic record has now been set for 'undersea in-tunnel shield machine shell abandonment and disassembly.' 　　The first shell abandonment and disassembly of the shield machine inside the undersea tunnel of the Xiamen Metro Line 3 cross-sea section has been successfully completed, creating a miracle of completing 'in-tunnel shield machine shell abandonment and disassembly' in 30 days.
　　In order to open up a reverse excavation working face for the mining method in the cross-sea section and create favorable conditions for subsequent construction, the China Railway General Contracting Project Department required the contractor, China Railway First Group's Xiamen Cross-Sea Passage Project, to control the machine dismantling schedule within one month. This involved the safe dismantling of the shield machine with a cutterhead diameter of 7.02 meters, a total length of 107 meters, and a weight of about 800 tons, along with its backup systems, and transporting them to Liuwudian Station 1.4 kilometers away.
　　To accomplish this almost impossible task, under the leadership of He Weiguo, deputy general manager of China Railway First Group Urban Rail Company, the project department invited internal and external experts to the site to demonstrate and guide the formulation of the 'Special Safety Construction Plan for In-Tunnel Machine Dismantling,' conducted tabletop drills for shield dismantling, carried out on-site training and briefings, and held pre-shift briefings for dismantling. Project manager Luo Jinhai introduced that to ensure the smooth progress of 'undersea in-tunnel shield machine shell abandonment and disassembly,' the project specially customized heavy-duty flatbed trucks from other places to achieve large-tonnage in-tunnel transportation, solving the transportation problem of the main drive weighing about 65 tons after cutting; through repeated calculations, they developed an inclined cutting angle method without rotating the cutterhead, overcoming the technical difficulty of cutting the cutterhead spokes.
　　Deputy project manager Mao Zhixin told reporters that before dismantling, detailed briefings were given on the layout of lifting points, welding quality of lifting points, protection during pipeline removal, cutting of partitions, and erection of work platforms; before hot work, firefighting facilities were required to be in place before construction could proceed; during hot work, real-time monitoring of gases in the tunnel was carefully carried out to ensure safety.
　　During the interview, Huang Gang, deputy director of the Technical Department of the Urban Rail Company's Tunneling Equipment Technology Center, said that since 'undersea in-tunnel shield machine shell abandonment and disassembly' was the first of its kind in China, most shield team employees had no experience in this area. For briefings on complex component removal, Zhao Junjun, deputy chief engineer of the center, had to repeat the handover several times and only left after confirming that everyone understood.
　　To ensure the smooth progress of the dismantling work, in addition to strictly implementing leadership shift supervision, the project department changed the original 'two-shift system' to a 'three-shift system,' shortening the working hours of dismantling personnel and reducing labor intensity, and arranged safety officers to stand by on site to ensure safety without fail. In addition, while installing ventilation pipes in the tunnel, the project department added a high-power electric fan for ventilation every 100 meters, and supplied mung bean soup and Huoxiang Zhengqi water to prevent heatstroke for workers in the tunnel, and distributed salt tablets, mineral water, Red Bull, etc. to replenish the physical strength of dismantling personnel, providing strong guarantees for completing the dismantling work on schedule. The first shell abandonment and disassembly of the shield machine inside the undersea tunnel of the Xiamen Metro Line 3 cross-sea section has been successfully completed, creating a miracle of completing 'in-tunnel shield machine shell abandonment and disassembly' in 30 days.
　　In order to open up a reverse excavation working face for the mining method in the cross-sea section and create favorable conditions for subsequent construction, the China Railway General Contracting Project Department required the contractor, China Railway First Group's Xiamen Cross-Sea Passage Project, to control the machine dismantling schedule within one month. This involved the safe dismantling of the shield machine with a cutterhead diameter of 7.02 meters, a total length of 107 meters, and a weight of about 800 tons, along with its backup systems, and transporting them to Liuwudian Station 1.4 kilometers away.
　　To accomplish this almost impossible task, under the leadership of He Weiguo, deputy general manager of China Railway First Group Urban Rail Company, the project department invited internal and external experts to the site to demonstrate and guide the formulation of the 'Special Safety Construction Plan for In-Tunnel Machine Dismantling,' conducted tabletop drills for shield dismantling, carried out on-site training and briefings, and held pre-shift briefings for dismantling. Project manager Luo Jinhai introduced that to ensure the smooth progress of 'undersea in-tunnel shield machine shell abandonment and disassembly,' the project specially customized heavy-duty flatbed trucks from other places to achieve large-tonnage in-tunnel transportation, solving the transportation problem of the main drive weighing about 65 tons after cutting; through repeated calculations, they developed an inclined cutting angle method without rotating the cutterhead, overcoming the technical difficulty of cutting the cutterhead spokes.
　　Deputy project manager Mao Zhixin told reporters that before dismantling, detailed briefings were given on the layout of lifting points, welding quality of lifting points, protection during pipeline removal, cutting of partitions, and erection of work platforms; before hot work, firefighting facilities were required to be in place before construction could proceed; during hot work, real-time monitoring of gases in the tunnel was carefully carried out to ensure safety.
　　During the interview, Huang Gang, deputy director of the Technical Department of the Urban Rail Company's Tunneling Equipment Technology Center, said that since 'undersea in-tunnel shield machine shell abandonment and disassembly' was the first of its kind in China, most shield team employees had no experience in this area. For briefings on complex component removal, Zhao Junjun, deputy chief engineer of the center, had to repeat the handover several times and only left after confirming that everyone understood.
　　To ensure the smooth progress of the dismantling work, in addition to strictly implementing leadership shift supervision, the project department changed the original 'two-shift system' to a 'three-shift system,' shortening the working hours of dismantling personnel and reducing labor intensity, and arranged safety officers to stand by on site to ensure safety without fail. In addition, while installing ventilation pipes in the tunnel, the project department added a high-power electric fan for ventilation every 100 meters, and supplied mung bean soup and Huoxiang Zhengqi water to prevent heatstroke for workers in the tunnel, and distributed salt tablets, mineral water, Red Bull, etc. to replenish the physical strength of dismantling personnel, providing strong guarantees for completing the dismantling work on schedule.