China's first under-river high-speed railway tunnel began
construction yesterday. The 10.1-kilometer tunnel is part of the
Wuhan-Guangzhou passenger railway, running under the 210-meter wide
Liuyang River. The project is to be completed in four months.
Located to the east of Changsha, the capital city of Hunan
Province, the tunnel starts from the south side of Xiaoxiang West
Road and goes under several expressways and the Liuyang River, a
main waterway running through the central province.
The project is divided into two sections and contracted to two
engineering groups of the China Railway Engineering Corporation
respectively. The southern section includes the critical underwater
track and about 80% of the construction will adopt the method of
undercutting excavation.
The minimum distance from the top of the tunnel to the bottom of
the river is merely 13 meters. Additionally, the instability of
peripheral rocks will probably incur collapse and flooding during
construction.
A total of 90 pipes filled with cement slurry will be hammered
into the vault with a length of 18 meters, propping up the roof of
the tunnel. Calculations show the underwater section will require
1,575 such pipes.
According to Pan Shengqiang, deputy director of the Changsha
Reform and Development Commission, they abandoned a proposal to
build a bridge across the Liuyang River for several reasons. The
plan concerned so many government departments that it would have
been difficult to coordinate the construction. Moreover, running
through the center of Changsha City, the proposed bridge would have
imposed a negative image on urban planning and economic
development.
The construction of the southern section has started in five
directions, and some 600 workers are working around the clock to
excavate 2.4 meters per day in each direction.
The Liuyang River portion is to be completed in four months, and
the 5.1-kilometer southern section will be finished by the end of
August next year to link up with the new railway station of
Changsha.
(China.org.cn by Huang Shan November 30, 2007)