On August 25, as the "Dongfanghong No. 2" shield machine successfully broke through the wall, it marked the smooth completion of the left-line tunnel of the shield-driven section from Lindun Road Station to Soochow University Station of Bid Section 6 of Suzhou Rail Transit Line 6, constructed by China Railway 16th Bureau Group. This is another key major milestone for the project following the topping-out of the main structure of Soochow University Station. At this point, the entire Suzhou Rail Transit Line 6 has achieved tunnel breakthrough, and the project has entered its final sprint stage, taking an important step toward achieving operational service.

As a key construction project of Jiangsu Province and Suzhou City, Suzhou Rail Transit Line 6 is a major project serving the integrated development strategy of the Yangtze River Delta. The line has a total length of 36.12 kilometers, starting at Suzhou New District Railway Station in the west and ending at Xinqing Road Station in Suzhou Industrial Park in the east, running northwest to southeast.

Among them, the main line of Bid Section 06, constructed by the Rail Company, has a total length of 2.7 kilometers and includes three stations and three sections: Xuanqiaoxiang Station, Lindun Road Station, and Soochow University Station; the shield-driven section from Zhuozhengyuan Station to Xuanqiaoxiang Station; the shield-driven section and open-cut passage from Xuanqiaoxiang Station to Lindun Road Station; and the shield-driven section from Lindun Road Station to Soochow University Station.

The section completed this time, from Lindun Road Station to Soochow University Station (referred to as the "Lin-Su section"), passes through the core area of Suzhou's Gusu old city, where the surrounding environment is complex and construction is extremely difficult. During construction, the shield machine successively passed beneath old residential buildings with shallow foundations multiple times over short distances, then passed beneath the existing operating Lindun Road Station of Line 1, continuously cutting through ancillary retaining bored piles, main structure column piles, and main retaining underground diaphragm walls, and finally reached the receiving shaft at Lindun Road Station of Line 6. Along the route, there was great pressure from traffic diversion, dense underground pipelines, excessively narrow enclosed sites, and numerous risk sources.

To ensure the smooth completion of the Lin-Su section, the construction team established a progress promotion working group. Through measures such as setting up trial sections and strictly controlling settlement data, and through repeated analysis and demonstration, they summarized effective and stable tunneling parameters, completing the small-radius, long-distance passage beneath 68 old buildings and cultural heritage protection buildings, with monitored deformation controlled within 5 millimeters.

During tunneling, the project working group organized expert demonstrations six times, improved the reinforcement plan and the configuration plan for the shield machine's cutterhead and cutters, and ultimately adopted a composite frozen cutterhead to reinforce the crossing area before directly grinding through piles and cutting through walls. They completed the passage beneath the bored pile retaining structure of the entrance/exit of the operating subway station within a short distance of 58 meters, successfully crossing the concrete diaphragm wall of the existing Lindun Road Station of Line 1, achieving a new breakthrough in continuous multiple pile-cutting and wall-grinding construction over a short distance.

Considering the difficulty of grinding through walls and cutting through piles, the project technical team, under conditions where conventional reinforcement and chamber-opening cutter replacement were not possible, added a frozen cutterhead configuration and formulated a dedicated emergency plan for opening the chamber and replacing cutters with a frozen cutterhead. They successfully developed a unique design featuring a frozen cutterhead with four levels of cutter height difference, heavy-duty tearing cutters, and edge roller cutters, achieving the first domestic case of pile-cutting and wall-grinding without cutter replacement, providing guidance for future shield tunneling through underground diaphragm walls of similar types.

It is reported that Suzhou Rail Transit Line 6 is an important passenger flow corridor running east-west through the ancient city and Jinji Lake in Suzhou, and is expected to open for operation in 2024. After the line is operational, it will greatly improve the quality of transportation between the east and west banks of Jinji Lake, stimulate new vitality in Suzhou's ancient city, accelerate the integrated development of the city, and help build a "Suzhou on Rails."