China has completed a new super-large shield tunneling machine designed for demanding underground and underwater projects.
The machine rolled off the production line in Zhengzhou, Henan Province, on Tuesday, marking the latest development in the country’s large-scale tunneling equipment sector.
With an excavation diameter of 16.68 meters, it is the largest-diameter shield machine independently developed by China to date, according to CCTV News.
The machine is 125 meters long and weighs about 4,800 tonnes. China Railway Tunnel Group, China Railway No. 4 Engineering Group and China Railway Engineering Equipment Group jointly developed the equipment. Its size gives it a wide excavation face, while its control systems are designed to handle difficult underground conditions.
A key feature is its full-face constant-pressure cutter head. The system allows workers to replace cutting tools while maintaining constant pressure inside the cutter head area. It is designed to support cutter replacement in environments with pressure of up to eight bar, reducing the need to expose workers to sudden pressure changes.
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The machine also uses a circulating slurry discharge system to remove excavated material. Its design combines direct discharge through a screw conveyor with crushing outside the main working chamber. This arrangement allows slurry pumps to move the excavated material efficiently and reduces the need for workers to enter the chamber to repair the crusher.
Built For Underwater Work
The equipment is intended for projects where tunneling conditions can change sharply along the route. Such work can involve steep slopes, tight curves and long sections beneath water. These conditions require the machine to maintain accurate alignment while adjusting its position during excavation.
Despite its large diameter, the machine is designed to negotiate small-radius curves. Hydraulic floating support devices in the propulsion system help the machine adjust its position as it advances. A high-precision guidance system and a segment selection system also help control the tunnel’s direction and the placement of its concrete lining segments.
These systems are important because large shield machines must maintain precise control as they move through the ground. The guidance equipment tracks the machine’s position, while the propulsion system adjusts its movement through hydraulic cylinders. These features allow the machine to manage changes in direction without sacrificing excavation control.
Precision On Curved Routes
China has invested heavily in large shield machines as it expands high-speed rail networks and urban transport links.
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The equipment is particularly relevant to projects that require tunnels beneath rivers, where high water pressure and difficult geological conditions add to construction challenges. The Zhengzhou machine adds another large-diameter platform to China’s growing domestic tunneling equipment capabilities.
Another super-large slurry balance shield machine was completed in Hangzhou, Zhejiang Province, in August. That machine has a diameter of 13.72 meters and a length of 145 meters and was developed for high-speed railway construction. The comparison shows the range of large shield equipment now being developed for different tunnel designs and operating conditions.
China Expands Tunnel Capacity
One major project using large shield technology is Nanjing’s first high-speed railway cross-river tunnel. The overall railway project extends about 20.4 kilometers, including a tunnel section of roughly 14 kilometers. The design uses a single tube carrying two high-speed railway tracks.
The tunnel will pass beneath the Yangtze River bed for an extended distance. At its deepest point, the tunnel will be buried about 107 meters below the surface and face water pressure of up to 1.07 megapascals. These figures make it the deepest and highest-pressure railway shield tunnel along the Yangtze River to date, according to the information provided.
The river crossing will be excavated by two slurry shield machines working from opposite ends. The machines are scheduled to meet with high precision and will then be dismantled on site at a location about 30 meters below the floodplain on the northern bank of the Yangtze River.
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The latest machine from Zhengzhou reflects the technical requirements of this type of construction. Its large excavation diameter, pressure-control features, slurry handling system and steering equipment are aimed at projects where space, water pressure and alignment all present challenges.
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