On the shores of East Lake in Wuhan, Hubei Province, China, a steel beast clad in "tiger-stripe" armor is silently advancing at a rate of several meters per day, carving an unprecedented double-deck underground passage deep beneath the lake. This is the "Zhengxianhao" (Striver), currently the world's largest diameter slurry shield boring machine. With its successful launch in the Wuhan Two Lakes Tunnel—the world's largest urban lake-bottom double-deck tunnel—a revolution in urban underground space construction is moving from blueprint to reality.
Super Project Demands Super Equipment
The Wuhan Two Lakes Tunnel spans approximately 19.45 kilometers with a total investment of about 25.4 billion yuan. This super tunnel, passing beneath East Lake and South Lake, is not only the longest urban lake-bottom tunnel in China and the largest of its kind in the world, but also an "underground aircraft carrier" featuring a double-deck design.
However, behind this super project lies extraordinary construction difficulty. The tunnel has a maximum gradient of 40‰ and a minimum turning radius of just 700 meters, following an S-shaped alignment. The tunnel boring machine (TBM) must excavate through long-distance mudstone strata, traverse areas with strong karst development, and face complex geological challenges such as solution cavities and fault fracture zones. The interplay of large cross-sections, tight curves, long distances, and complex strata places the project's comprehensive technical difficulty among the highest internationally.
To conquer this "geological maze," China Construction Third Engineering Bureau Co., Ltd. (CCTEB) partnered with China Railway Engineering Equipment Group Co., Ltd. (CREG) to custom-build this engineering "beast"—the "Zhengxianhao."
Three Core Innovations Forge a "Lake-Crossing Tool"
World-Class Size and Precision
The "Zhengxianhao" has an excavation diameter of 15.094 meters, a total machine length of 115 meters, and a weight of 4,300 tons—equivalent to the weight of six subway cars or 3,000 sedans. These dimensions make it one of the world's largest diameter slurry shield TBMs currently in operation.
"Articulated Sliding Cylinder" Enables Simultaneous Excavation and Segment Assembly
CCTEB's self-developed continuous excavation and synchronous segment assembly technology, relying on a unique "articulated sliding cylinder" design, cleverly separates the excavation zone from the assembly zone. These two core processes operate simultaneously without interference, effectively equipping the TBM with flexible "cooperative joints," boosting construction efficiency by 20% to 30%. Under complex conditions like sharp turns, it can switch back to conventional mode with one click and is adaptable to different diameters of earth pressure balance and slurry shield TBMs, allowing for retrofitting of older equipment.
"Smart Brain" Enables Full-Process Intelligent Control
Beyond hardware, the "Zhengxianhao" possesses a "smart brain." CCTEB's self-developed shield intelligent management platform achieves "one map for management, one map for construction"—pressing the Enter key displays the working status of the TBM fleet at a glance; a simple mouse click reveals excavation parameters and risk source locations. The platform integrates closed-loop control of warnings, handling, and approval, enabling one-click analysis of work efficiency, parameters, and assembly quality, making safety, quality, and progress management precise and controllable.
Customized "All-Round Skills" for Complex Conditions
To handle the complex and variable construction environment beneath the lake, the "Zhengxianhao" incorporates numerous cutting-edge technologies:
Atmospheric Cutterhead: Allows workers to safely and efficiently change cutting tools without operating in a high-pressure environment, significantly reducing high-risk operation hazards.
Screw Conveyor Direct Discharge Dual-Channel Design: Effectively reduces the risk of clogging in the chamber and significantly decreases the probability of mud cake formation on the cutterhead. Equipped with a new front-mounted axial disc cutter and a real-time tool condition monitoring system, tool change operations are safer and more efficient.
Advance Geological Prediction System: Acts like a pair of "X-ray eyes," capable of foreseeing unknown geological risks ahead.
Automatic Mud Cake Removal System: Effectively ensures the TBM maintains continuous and rapid excavation in composite strata, avoiding downtime risks caused by mud cake formation on the cutterhead.
Reshaping the New Landscape of Urban Underground Transportation
Breaking the "Dead-End Road" Dilemma in Wuchang
Once completed, the Wuhan Two Lakes Tunnel will reduce the average spacing of north-south arterial roads in central Wuchang from 4-5 kilometers to approximately 2 kilometers. This change will significantly enhance urban commuting efficiency, effectively divert pressure from the existing road network, and bring a qualitative leap to Wuhan's urban transportation.
Setting a New Benchmark for Urban Lake-Bottom Tunnel Construction
The successful application of the "Zhengxianhao" provides valuable technical accumulation and experience reference for future construction of ultra-large diameter tunnels beneath urban lakes and seas. From the launch of the "Zhengxianhao" to the maturation of synchronous segment assembly technology, China's ultra-large diameter shield tunneling technology is advancing to the global forefront.
Large-Scale Application of Full-Diameter Shield Complete Technologies
CCTEB has mastered complete technologies for "extra-large, large, medium, small, and micro" diameter shields, having participated in the construction of 400 kilometers of subway lines across 25 cities in 13 provinces. The formation of this technology matrix signifies that China's urban underground space development now possesses full-spectrum equipment support capabilities, ranging from "minimally invasive surgery" to "super projects."
A Leap from "Experience-Driven" to "Model-Driven"
The birth of the "Zhengxianhao" is not just the success of a single piece of equipment but also a microcosm of China's high-end equipment manufacturing industry transitioning from "experience-driven" to "model-driven." Empowered by the "Pioneer·Industrial Manufacturing Large Model" launched by China Railway Industrial Co., Ltd., shield TBMs are becoming more "perceptive and intelligent." This AI large model, specifically designed for industrial manufacturing, builds a full-chain intelligent system of "computing power—algorithm—data—platform—application," enabling second-level analysis of equipment faults and one-click generation of multiple optimized design solutions.
As the 15.094-meter "Zhengxianhao" silently traverses the shores of East Lake, it is excavating not just a tunnel, but a new height for China's urban underground space development. From a follower to a leader, China's ultra-large diameter shield tunneling technology is writing its own world standards.