Double shield TBM for Thailand water tunnel 28 Jul 2016

A 4.9m diameter double shield TBM is designed by Seli Technologies and manufactured by Sany of China for excavation of a 10.5km long tunnel for Contract 2 of the Mae Ngat-Mae Kuang Water Diversion Tunnel Project in Thailand.

Senior managers of Unique Engineering and Construction Ltd and advisers join senior managers of Seli and Sany for factory testing of the double shield TBM

The TBM is procured by Thai contractor Unique Engineering and Construction Public Company Ltd following award of Contract 2 on the first phase of the water delivery tunnel project to convey water from the Mae Ngat reservoir to the Mae Kuang reservoir on the Mae Ping River system in the mountainous region of northern Thailand.

Awarded by the Royal Irrigation Department of Thailand, the 10.5km long TBM tunnel drive by Unique Engineering and Construction is the downstream half of the total 23km long tunnel of Phase 1 of the project. Thai contractor ItalThai is awarded Contract 1 for the upstream half of the tunnel from an intake at the Mae Ngat reservoir to a junction with the Unique Engineering and Construction tunnel.

A second phase of the project will develop a further scheme to divert water from the Mae Tang River to the Mae Ngat revervoir through an additional 25.5km of 4m diameter tunnelling (Fig 1).

The Seli designed TBM will progress through mainly thick-bedded sandstone intercalated with shale and siltstone with zones of weathered, faulted and fractured rocks identified along the alignment and beneath an overburden that ranges from 20m to 758m. As the TBM progresses, it will erect a precast concrete hexagonal segmental lining.

The machine will launch at the downstream portal and will progress on a slight uphill gradient to the interface with the Contract 2 drive. To optimise progress, the TBM is planned to operate in the true double-shield mode with grippers in the gripper shield allowing the lining to be built in the rear shield and permit concurrent lining with excavation.

Fig 1. Map of the full Mae Tang-Mae Ngat, Mae Ngat-Mae Kuang Water Diversion Project with the Unique Engineering and Construction contract covering the 10.5km long downstream section of the Phase 1 Mae Ngat-Mae Kuang tunnel

The 4.9m diameter TBM was manufactured in the vast Sany factory in Beijing and is the first TBM produced by the company. Sany manufactures all types of heavy construction equipment and in 2012 bought the Putzmeister concrete pump manufacturer of Germany. At a factory testing visit in Beijing on 8 July, Unique Engineering and Construction CEO Prasong Suviwattanachai congratulated Seli-Sany on manufacture of the machine. The cutterhead was manufactured and supplied by Palmieri of Italy and joined other components sourced and manufactured in China.

Unique Engineering and Construction Public Company is one of the largest civil construction companies in Thailand. The Mae Ngat-Mae Kuang Water Diversion Tunnel Contract 2 is its first tunnelling project. Mobilisation of the work site is well advanced and production of segments has begun at the on-site casting yard.

The machine is currently being dismantled at the Sany factory in Beijing for shipment to Thailand and transport to the high mountainous site for assembly and an anticipated start of tunneling by the end of the year (2016).

The budget for the full project is estimated at in excess of 17,000 million baht (US$485 million) with the Mae Ngat-Mae Kuang Phase 1 tunnel project estimated at 7,000 million baht (US$200 million) and the Mae Tang-Mae Ngat Phase 2 tunnel estimated at 8,000 million baht (US$228 million). Each diversion tunnel project is expected to take five years to complete.