Page 152 - 捷運技術 第44期

146 孫吉甯 常輝庭 捷運跨河隧道及道岔工程施工－以臺北捷運CK570C標工程為例

Construction of River-Crossing Tunnels and Turnout Work

for Taipei MRT － Taking Contract CK570C of the Xinzhuang

Line as an Example
1
Sun Chi-ning Chang Huei-ting 2
Abstract

This article describes the construction of river-crossing tunnels and the turnout section
of the Xinzhuang line Section Contract CK570C, a crucial section of the Taipei MRT “Three

Rings & Three Lines.” As the section is a crucial point where the Xinzhuang and Luzhou
lines enter New Taipei City's Sanchong, Xinzhuang, and Luzhou districts, a deep excavation
is needed at the cut-and-cover tunnel's turnout section beneath the Danshui River which
separates Taipei City and New Taipei City. A cofferdam was built in the river to provide
working space for open-cut excavation, construction machines and tools. The turnout, the

branch line fork of the Xinzhuang line and Luzhou line, is 125m long, 41.5m deep and
gradually changes from 15m to 26m in width, of which 40m of the length is located beneath
Huanhe N. Rd. inside the levee bank while the other 85m runs in the area beyond the levee.

The section is a four-level underground structure with a 41.5-m-deep excavation. Some
special construction methods, such as bottom sealing grouting, a 2-m-thick diaphragm
wall, and large-scale dewatering, were applied to this work to overcome underground earth
pressure, water pressure and upwelling force.

Sand upwelling and water upwelling were typical problems during the tunnel entrance
frame excavation, especially in deep areas with high earth and water pressure. Due to the
uncertainty of the grouting effect, these problems could cause serious damage to the entrance

frame and result in construction failure. There were a total of eight tunnel entrance frames
2
at depths ranging from 32.5m to 23m and water pressures from 23 to 32 t/m . The freezing
method with high pressure jet grouting was applied to assure the effect of the water seal
during the tunnel entrance frame excavation. The high difficulty and risky construction made

Section Contract CK570C the first of its type in the nation. The successful experience is truly
beneficial to the enhancement of technology in domestic construction.

Keywords: turnout, cofferdam, JSP piles, diaphragm walls, bottom sealing grouting, large-
scale dewatering, shield tunneling method, high pressure grouting, freezing
method

2011/10/21 下午 06:16:46
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