CREC 1112, developed and manufactured by China Railway Engineering Equipment Group (CREG), broke through on the pipe jacking section of N-Standard-Partition Street Interchange C-Traffic-Node A-Ramp project in Chongqing Liangjiang New Area. The project links Lushan Avenue near the North Square of Chongqing North Railway Station and the Chongqing Inner Ring Expressway.

CREG says it is the first time a large cross-section rectangular pipe jacking machine has completed full-face excavation, solving the problem of blind area excavation, especially in hard rock strata, by a non-circular TBM.

CREC 1112 is 10.42m wide and 7.57m high. It is equipped with six circular cutterheads and six drum cutters, meaning the tunnel face is completely covered.

CREG team also customised the machine’s settlement control and attitude control systems to provide stronger rock breaking capability and tunnelling performance, and minimise ground disturbance. This was particularly important as the tunnel passes under two, two-lane roads and has a shall overburden of only 4-5m.

To deal with these challenges, CREG equipped the machine with three intelligent systems to provide remote control: the intelligent thrust system; soil conditioning system; and friction reduction system. They can precisely control the cutterheads and shield articulation cylinders and provide real-time adjustment of advance direction. They also provide dynamic monitoring of muck and friction reduction material coefficient.

The machine has a maximum monthly advance rate of about 30m, which CREG says approximately halves the construction period and saves 60% in labour cost compared with hand excavation. It also improves safety.