In July 2026, at the production base of China Railway Hi-Tech Intelligent Equipment Co., Ltd. in Xinjin District, Chengdu, Sichuan Province, a "steel dragon" with a diameter of 13.01 meters is entering the final assembly sprint. This is the world's largest double shield tunnel boring machine (TBM) of its type, expected to complete final assembly and officially roll off the assembly line by the end of this month. At that time, this "giant" will set a new global size record for double shield TBMs.

Hardcore Parameters: Thrust Force of 7,900 Tons, Equivalent to the Combined Force of 200,000 Family Cars

This "Chengdu-made" world's largest double shield TBM has a total length of 220 meters and integrates cutting-edge technologies such as intelligent sensing, precise excavation, and safety prevention and control. Its core performance parameters are astonishing:

Thrust force reaches 7,900 tons, and torque exceeds 40,000 kN·m, equivalent to the combined force of 200,000 family cars

The core component, the "main drive," weighs 400 tons and can be raised by 100 mm in a confined tunnel to increase the excavation diameter, effectively mitigating the risk of the machine getting stuck by tunnel rock walls or jamming during excavation

The machine body adopts an inverted cone design to further reduce the risk of jamming

This equipment is manufactured at the production base of China Railway Hi-Tech Intelligent Equipment Co., Ltd. in Xinjin District, Chengdu. It is China's first fully independently developed and produced world's largest double shield TBM.

Technical Highlights: Double Shield Structure Enables Simultaneous Excavation and Lining

The double shield TBM is hailed as the "king of all-round excavation" among the three types of TBM models (open type, single shield, and double shield). This "giant" integrates the dual advantages of open and single shield TBMs, with its core technical highlights reflected in:

Double Shield Dual Propulsion System: The equipment is equipped with a front shield (excavation shield) and a rear shield (support shield). The front shield is at the forefront, housing the cutterhead, main drive system, and stabilizers, responsible for rock cutting and breaking; the rear shield contains the gripper system, auxiliary thrust cylinders, and segment assembly area. In hard rock construction, the main propulsion system pushes the machine forward by using grippers against the tunnel wall for reaction force; in fault fracture zones or soft rock areas with poor geological conditions where the tunnel wall cannot provide sufficient reaction force, the auxiliary thrust cylinders push against the installed concrete segments, using the segment reaction force to advance the TBM.

Telescopic Shield for Flexible Posture Adjustment: The middle of the equipment is connected by a telescopic shield, which can address the "extension" and "bending" issues between the front and rear shields, flexibly coordinating the machine's posture.

Intelligent Safety Prevention and Control System: The equipment is equipped with advanced geological detection devices and gas detectors to ensure operational safety under complex geological conditions.

Thanks to the core design of the double shield structure and dual propulsion system, this TBM can simultaneously advance processes such as excavation, lining installation, and surrounding rock support, improving construction efficiency by 3 to 5 times compared to traditional drill-and-blast methods. The fully enclosed shield construction mode also effectively reduces the frequency of shutdown inspections, further enhancing the comprehensive utilization rate of the equipment.

Challenging Sichuan's Longest Highway Tunnel

This "national heavy equipment" will be used for excavating the Yuexi Tunnel on the Jinxi Expressway (Jinkouhe to Xichang Expressway). The Yuexi Tunnel is located at the border of Yuexi County and Xide County in the Liangshan Yi Autonomous Prefecture, Sichuan. It features a separated double-tube design, with a left tube length of 18.39 km and a right tube length of 18.38 km, and a maximum burial depth of 1,011 meters. This tunnel is currently the longest highway tunnel under construction in Sichuan.

The tunnel construction adopts a "TBM + large machinery support" combined method: the right tube uses large machinery support, while the left tube introduces this world's largest diameter double shield TBM for excavation. This will be the first tunnel in China's highway engineering field to use a large-diameter double shield TBM for main tunnel construction.

Due to single-head excavation, hard rock, soft rock, and cohesive soil layers alternate along the route, making the geological conditions extremely complex. The double shield TBM is precisely the "sharp tool" for handling various complex geologies—relying on grippers for reaction force to achieve high-speed excavation in hard rock, and switching to segment support mode to continue advancing in soft strata, ensuring full tunnel breakthrough.

The Jinxi Expressway has a total length of approximately 211.6 km, with a bridge-tunnel ratio as high as 75.55%. Once completed, it will end the history of no expressway access for the three counties of Ganluo, Yuexi, and Xide in Liangshan Prefecture, opening a new corridor from Chengdu to Xichang and Yunnan, and enhancing Sichuan's southward outbound capacity.

"Xinjin-Made" Going Global

The birth of this world's largest double shield TBM marks the rapid development of China Railway Hi-Tech Intelligent Equipment in Chengdu. In September 2023, the company settled in Xinjin District and built the first intelligent final assembly production line for full-face tunnel boring machines in Southwest China in less than two years. It is also the only equipment manufacturing base in Southwest China with full-process production capabilities for high-end shield machines. Once fully operational, the base can produce 14 shield machines, 50 sets of tunnel construction specialized equipment, and 50,000 tons of steel structures annually, with an estimated annual output value of 1.8 billion yuan.

Currently, Xinjin has gathered over 100 "chain leaders" and upstream and downstream rail transit enterprises, including China Railway Hi-Tech, CRRC Changchun Railway Vehicles Co., Ltd. Chengdu, and XinZhu Co., Ltd., with an annual output value exceeding 10 billion yuan, forming a full-chain industrial ecosystem covering R&D and design, core components, and intelligent operation and maintenance. The market share of shield machines from parent company China Railway Hi-Tech Industry Corporation Limited has ranked first in the world for eight consecutive years. In July 2025, Sichuan's first fully chained "Xinjin-made" earth pressure balance shield machine, "Chuanshanjia No. 1," rolled off the assembly line at the Xinjin base. Customized for extreme low-temperature environments of minus 40 degrees Celsius, it was exported to Europe for use in high-latitude water conservancy projects.

More and more "Chengdu-made" and "Xinjin-made" products are becoming important forces in national infrastructure, continuously solidifying Xinjin's industrial position as a key hub for high-end intelligent equipment manufacturing in Southwest China.