By Rose Bell
Being innovated and manufactured by China Railway Engineering Equipment Group(CREG) and is the world’s first hard rock rectangular pipe jacking machine, CREC 1112 has broken through on the pipe jacking section of N-Standard-Partition Street Interchange C-Traffic-Node A-Ramp project in Chongqing Liangjiang New Area, whereas this project connects Lushan Avenue near the North Square of Chongqing North Railway Station and the Chongqing Inner Ring Expressway.
According to CREG : “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.”
With 10.42m wide and 7.57m high, CREC 1112 is equipped with six circular cutter heads and six drum cutters, meaning the tunnel face is completely covered.
Additionally, in order to providing stronger rock breaking capability and tunnelling performance, and minimising ground disturbance, CREG team customised the machine’s settlement control and attitude control systems, that was particularly important as the tunnel passes beneath two-lane roads and must has a overburden of only 4-5m.
Considering that these challenges should be overcome, 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 cutter heads and shield articulation cylinders and provide real-time adjustment of advance direction. They also provide dynamic monitoring of muck and friction reduction material coefficient.
With a maximum advance rate of almost 30m per months, this machine around halves the construction period and saves 60% in labour cost compared with hand excavation. It also improves safety.
