Four CREG TBMs Break Through at Shenzhen Metro Line

A CREG double-shield TBM (“CREC383”) mining an access tunnel of Lot 6111 on Shenzhen Metro Line 6 successfully broke through on April 10, 2019, marking successful application of double-shield TBMs independently developed by CREG (China Railway Engineering Equipment Group Co. Ltd.) to urban metro construction.

Four TBMs including CREC287, CREC288, CREC382 and CREC383 have been used on the Shenzhen Metro. CREC287, a double-shield TBM officially launched in Meichuang section of Shenzhen Metro Line 10 on Feb 15, 2017, was the first double-shield TBM independently developed by China to be used in urban metro excavation.

The excavation drive is mainly composed of weakly weathered and partially moderately weathered granite. The actual maximum compressive strength is over 150 MPa and the quartz content is more than 70%. With low overburden, the tunnel underpasses a metro line, railway and other projects. Along the tunnel, the geological conditions are complex with several faults and structural fracture zones, high rock strength and variable stratum along the alignment.

Adhering to the team concept of “crossing mountains and tunneling through the world,” CREG’s TBM R&D team went to the site for full survey, careful analysis and comprehensive simulation. They also conducted targeted design of new technologies like a cutterhead with high efficiency, efficient material transport capacity, extendable belt conveyor, cold-charge over cutter support, main drive with a passage (a passage at the bottom of cutterhead for field staff to carry out cutterhead maintenance) for hard-rock excavation. Consequently, CREG set a new record of radial over-excavation volume of 100 mm, continuous over-excavation of 700 m and Asia’s smallest radius curve. By all above efforts, technological support has been given to the four TBMs to ensure smooth and efficient tunneling.

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To meet the special geological requirement of Shenzhen Metro Line 6, CREC383 is challenged with a small radius curve (260 m). However, there was no reference case of TBM with less than 260 m small radius curve in the world. In order to solve the difficulty, CREG’s TBM R&D team made targeted innovation design on cutterhead over-excavation, shield structure, thrust system control and segment erection. In equipment construction phase, CREG engineer Qi Zhichong, member of the R&D team, travelled to the site many times for technological support, aiming to ensure smooth excavation with small radius curve.

Finally, CREG successfully solved technological difficulty of double-shield TBM with small radius curve (260 m), and maximum turning distance of 710 m, thus making it the TBM tunnel with longest continuous turning distance in China.

This report was contributed by China Railway Engineering Equipment Group Co. Ltd.

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CREG Double-Shield TBMs on Shenzhen Metro
Project	Launch Time	Breakthrough Time	Construction Time
CREC287	Feb. 5, 2017	Dec. 25, 2018	Approx. 1 year and 10 months
CREC288	May 1, 2017	Mar. 28, 2019	Approx. 1 year and 11 months
CREC382	Mar. 28, 2018	Feb 20, 2019	Approx. 11 months
CREC383	May 25, 2018	April 10, 2019	Approx. 11 months