In the spring of 2018, in Changde's urban area, the construction of the Yuanjiang River tunnel was already in full swing.
This is the largest underwater shield tunnel in the province.
The shield tunneling machine is manufactured by China Railway Construction Heavy Industry Group Co., Ltd.
On February 23, the author drove here to witness the power of the shield machine.
Entering the construction site and putting on a safety helmet, the author couldn't wait to see the star of tunnel construction—the first domestic atmospheric cutter change super-large diameter slurry balance shield machine, "Yuan'an Hao."
"It's working now, and 236 meters have been excavated so far," said Zhang Keqiang, service manager of the Changde Yuanjiang Tunnel Project for CRCHI, glancing at his phone and speaking to the author.
The author leaned in and saw it was a "shield machine remote monitoring system" app. "Construction units and owners can both use this system to understand the shield machine's operation in real time."
Shortly after entering the tunnel, Zhang Keqiang told the author that the shield machine was ahead. It turns out that, apart from the most frequently seen cutterhead, the shield machine also includes the shield body, trailers, connecting bridges, slurry and gravel transport equipment, etc., with an overall length of 132 meters and a total weight of about 3,000 tons—a true "giant."
Accompanied by the rumbling of machinery, the author walked to the front of the shield machine. Through the monitoring port of the excavation chamber, the cutterhead could be seen rotating and tunneling, carrying broken sand and gravel.
"The cutterhead diameter is 11.75 meters—not only super large but also beautiful. Of course, you can't see it from this angle now," Zhang Keqiang said with a smile. "The cutterhead of 'Yuan'an Hao' looks like a blooming peach blossom, so it is called 'the most beautiful shield machine in history.'"
This shield machine is not only highly attractive but also highly capable.
"Yuan'an Hao" possesses the unique skill of atmospheric cutter change. Previously, if a slurry shield machine needed to replace cutters, the pressure chamber behind the cutterhead had to be pressurized to ensure pressure comparable to the geological environment. Workers, "fully armed," replaced cutters in a high-pressure environment twice normal atmospheric pressure, posing a high risk. "Yuan'an Hao" uses a gate to cut off the connection between the cutterhead position and the outside, allowing workers to operate under atmospheric pressure, avoiding operational risks, improving efficiency, and reducing costs.
Zhang Keqiang introduced that more than 10 days ago, when inspecting the cutters, 21 cutters were replaced in only one and a half days; if under pressure, it would take at least 4 to 7 days, involving multiple衔接 tasks such as slurry replacement and filter cake formation on the excavation face, as well as real-time monitoring of ground settlement to avoid potential risks.
"Let's go see the shield machine's 'brain,'" Zhang Keqiang said, leading the author into the control room. The author saw that the shield machine console is divided into two parts: one is the propulsion system, and the other is the slurry circulation system. On each panel, more than 40 buttons and switches of different shapes are orderly arranged; on the display screen above, images from 15 monitoring points on the shield machine are clearly visible.
"Veteran operator" Liu Yuan started work on the third day of the Lunar New Year. At this moment, he was staring intently at the operation interface, where various values were constantly changing slightly. "11 mm/min, this is the tunneling speed; these six buttons can control the tunneling direction," Liu Yuan said, pointing and introducing to the author.
Thirty-one-year-old Liu Yuan has 10 years of shield machine operation experience and has operated more than 30 different types of shield machines. He introduced that at first he operated imported shield machines, but in recent years they have all been domestic. "Yuan'an Hao" is the largest shield machine he has ever operated.
"Is it easy to operate?"
"Quite easy!" Liu Yuan said. Compared with imported shield machines, "Yuan'an Hao" excels in the intelligence of its operating system, the stability of its propulsion system, and the smoothness of its slurry circulation system.
Zhang Keqiang introduced that at major project construction sites such as the Beijing-Shenyang High-Speed Railway, the Yu-Ji Intercity Railway, and the Beijing Metro New Airport Line, CRCHI's "underground drilling artifacts" are showing their prowess.
Breaking foreign monopolies and fully independently developed, CRCHI's TBM (rock tunneling machine) and large-diameter shield machines have reached a domestic market share of over 85% and have successfully gone abroad, demonstrating the strength of a national heavyweight.