Recently, the trailer gantries of the "Pioneer No. 9" and "Pioneer No. 10" shield machines in the Tianlan section of Chengdu Rail Transit Line 19 were successively lowered slowly into their predetermined positions underground. With this, all 32 shield machines for Phase II of Line 19 have been lowered into their shafts, opening a new chapter in shield tunneling.

The two shield machines lowered this time will launch from Tianfu Business District Station and extend eastward, passing beneath the China Overseas Panda Tower commercial planned plot, the Chenghua Line railway subgrade, and the Luxi River flood discharge channel, before reaching the shield shaft in the Tianlan section, where they will be lifted out. The section tunnel mainly passes through moderately weathered sandstone and moderately weathered mudstone strata and is a low-gas-risk area. This section adopts two earth pressure balance shield machines for simultaneous construction. "Pioneer No. 9" and "Pioneer No. 10," numbered 25# and 26#, have an overall length of 105 meters, a cutterhead excavation diameter of 8,640 millimeters, and a minimum tunneling curve radius of 350 meters. The shield machines are fully equipped with explosion-proof local fans and explosion-proof lighting equipment to meet low-gas explosion-proof design requirements. The shield body is equipped with a middle-shield mud injection system and a tail-shield synchronous two-component grout system, further enhancing tunneling stability and segment formation quality and minimizing ground settlement.

To ensure the smooth lowering of the shield machines, the construction company conducted strict review and inspection of the qualifications and certificates of special-operation personnel for shield hoisting and of crawler crane equipment. Key arrangements were made for the layout and initial value collection of monitoring points at the construction site, the setting of warning signs, markings, and lines in the hoisting area, the on-site duty personnel list for hoisting operations, and hazard identification boards. During the shield machine hoisting and lowering process, the "ten no-lift" principles for hoisting operations were strictly implemented. The trailer gantries and shield body were transported, hoisted, and assembled in sections. Riggers, construction workers, safety officers, and supervisors were present throughout the process, and the leader in charge of the work site was on duty throughout the entire process to ensure that the shield machine hoisting and lowering operations were carried out safely and orderly.

It is reported that, as of now, the entire Phase II of Line 19 has completed 5,518 retaining piles, 6,591,171 cubic meters of earth and rock excavation, and 636 floor slabs of the main structure; in the parking lot, 2,030,510 cubic meters of earth excavation has been completed in Areas A and B under the cover, along with 3,847 foundation piles and 30 floor slabs of the under-cover structure; the segment factory has produced 17,631 rings of segments; 32 shield machines have arrived on site, and 32 have been lowered into shafts, of which 28 are currently tunneling and 2 have achieved breakthrough, with a tunneling length of 13,329 meters. All work is progressing steadily.