The world’s first rectangular pipe-propelled tunnel boring machine (TBM) for hard rock has excavated and breached a 176-meter-long road tunnel under two major roads in Chongqing, China.
TBM developed and manufactured by China Railway Engineering Equipment Group (Creg), commonly known as Clek 1112, has an excavated section 10.42 meters wide and 7.57 meters high. It is equipped with 6 circular cutter heads and 6 drum cutters, which combine to achieve a unique rock crushing technology.
According to Clegg, the two-layer layout of the cutter head and drum cutter ensures complete coverage of the tunnel face, which solves the “blind drilling problem” of round-face TBMs, especially in hard rock formations. ” is reported.

CREC 1112 before use
It was used in the N-Standard-Partition Street Interchange C-Traffic Node A-Ramp project in Chongqing Liangjiang New Area. This road connects Lushan Avenue near Chongqing North Railway Station’s North Square with the Chongqing Inner Ring Expressway. Cut-and-cover techniques were not possible because it needed to pass under two major roads: the Chongqing Inner Ring Expressway and the Airport Road.
In addition, the tunnel had an “ultra-shallow earth cover” of only 4-5 meters below the road, making the work “very difficult”. Mr Clegg said the tunnel was also the longest pipe-jacked tunnel under a motorway and had strict requirements to control road subsidence.

CREC 1112 ready for release
The Clegg team therefore customized the TBM with a subsidence control system to provide more rock-breaking capability, ensuring it penetrates solid rock formations and minimizing ground disturbance.
The TBM is now equipped with three intelligent systems that are controlled remotely. This includes intelligent thrust systems, soil conditioning systems, and friction reduction systems. According to Clegg, these systems can efficiently and precisely control cutter heads and shield articulation cylinders, allowing real-time adjustment of heading and dynamic monitoring of sediment and friction-reducing material coefficients, allowing construction Improve efficiency.
According to Clegg, TBM advances at a rate of up to 30 million per month, cutting construction time in half and saving 60% in labor costs compared to hand excavation methods.

Tunnel excavated by CREC 1112
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