Two 4.74m diameter hard rock double shield TBMs will
complete more than 15km of complex tunnelling for the Mae Tang-Mae
Ngad water diversion project, in Thailand.
Australian-based TBM manufacturer, TERRATEC, celebrated the
delivery of two hard rock Tunnel Boring Machines (TBMs) for the second phase of
tunnelling on the Royal Irrigation Department’s Mae Tang-Mae Ngad water
diversion project, in northern Thailand, following successful factory
acceptance tests last month.
The robust 4.74m diameter TERRATEC Double Shield machines
will be deployed by Thai contractors Right Tunnelling Co. Ltd. and Siamphan
Enterprise PCL on two contracts – totalling over 15km of TBM driven tunnel –
for the 25km-long Phase 2 tunnelling works, which traverse the challenging
mountainous terrain north of Chiang Mai city.
These TBMs have been designed to confront the highly complex
and variable geology of the region, which ranges from granite, gneiss,
quartzite and schist, to sandstone, siltstone, shale, slate, mudstone and
claystone, and varies from massive to highly fractured and weathered rock
masses (with a UCS range of 8MPa to 220MPa), including numerous fault and
fracture zones and the potential for high ground water inflows.
In order to handle these challenging conditions, the tough
yet versatile TERRATEC cutterheads have each been equipped with heavy-duty 17”
disc cutters and feature large bucket openings, as well as anti-wear plates and
lubrication systems for the injection of foams and polymers to assist with wear
prevention and dust suppression. The 1,500kW Electric Variable Frequency Main
Drives (VFD) will allow the cutterheads to cut efficiently in harder rock zones
at a maximum speed of 9rpm and deliver 2,896kNm of torque of to cope with more
fractured zones of the alignment.
In addition, the machines are fitted with state-of-the-art
probe drilling systems, located behind ring gear style segment erectors, that
provide 360-degree coverage for probing and grouting of the ground ahead of the
TBMs; as well as dewatering pumps that have the capacity to manage groundwater
inflows of up to 100lt/sec.
“We are delighted to be working with TERRATEC as our
partner on this landmark water tunnel,” said Mr. Teerapon Wangmontri,
President of Siamphan Enterprise PCL. “Due to the complex geology
expected on the project, we wanted to choose a tried and tested manufacturer of
hard rock machines such as TERRATEC, whose double shield TBM experience is
exceptional.”
As the two machines progress along their respective
alignments, they will install precast concrete segmental lining rings
consisting of four x 1400mm wide honeycomb style segments, with an inner
diameter of 4m, which will be backfilled with pea-gravel and grouted in place.
Excavated muck and supplies will be conveyed via rail-bound systems.
The Mae Tang-Mae Ngad water diversion tunnel is
located about 55km north of Chiang Mai, in northern Thailand, and is designed
to convey 28 cubic metres per second of raw water from the Mae Tang River to
Mae Ngad and Mae Kuang reservoirs. The project aims to augment the current
water supply to the Chiang Mai and Lampun Provinces involving over 50km of
tunnel that is being built in two Phases.
When the overall project is complete, in 2021, a saving of
more than 160 million cubic metres of water will be seen each year. The extra
water will help support a range of industries and sectors, such as the consumer
sector, agriculture and tourism.
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For more information visit: www.terratec.co
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