On 25th, December 2015, the largest rectangular box jacking machine “Kai Tuo” independently developed and manufactured by China Railway Engineering Equipment Group Co., Ltd (CREG) was rolled off the assembly line of CREG’s factory in Dalian. With dimensions being 10.12 ×7.27m, the machine will be transported to Tianjin for the underpass construction of Subway Line 11.

Based on the adequate construction experience, CREG took a bold and innovative step. The three front and three back cutterheads of “Kai Tuo” are arranged with parallel shafts and the excavation area of adjacent cutterheads is overlapped. The excavation ratio (excavated area/tunnel cross-section area) can reach 95%. With relatively small cutterheads and individual excavated area, “Kai Tuo” causes little disturbance to the ground and therefore significantly lessens ground settlement.

In December 2013, the successful application of the Rectangular Box Jacking TBM developed by CREG to Zhengzhou Zhongzhou Avenue Undercrossing Tunnel Project drew industrial attention at home and abroad. Authorities from Singapore paid a study trip to CREG and showed intense interest in the safe and efficient construction, the effective use of space and the positive role of relieving the traffic pressure of Rectangular Box Jacking TBM. The two sides then signed the purchase contract for Singapore Thomson Line Project. The Rectangular Box Jacking TBM with dimension of 7.620×5.645m was rolled off the assembly line in Zhengzhou China on 28 October 2015. Its successful export to Singapore signified a breakthrough of domestic specialty shield machines going abroad.

Rectangular Box Jacking TBM, on account of its advantages like simple, safe and environmentally friendly construction technique, rapid progress, high utilization rate of cross section and shallow overburden, provides a new solution to the urban traffic tunneling for China and the world. Moreover, it gradually becomes a new main force in underground development and has a promising market in the future.