Page 44 - 捷運技術 第38期

38 尤柏文 黃幹鐘 楊鵬飛 林坤霖 淡水河堤外道岔結構深開挖袪水工法

Case Study of the Dewatering Methods for the Deep Excavation of Turnout

Structure of CK570C of the Taipei MRT
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Bo-Win Yu Kan-Chung Huang Pong-Fey Yang Lin-Kun Lin 4
Abstract

The site of the Xinzhuang MRT line turnout structure is located on the northern side of Taipei
Bridge and underneath both the inner and outer sides of the Danshui River dike. The turn-out
structure also lies beneath the elevated Huanhe Expressway in Sanchong and will be used as a track
switch for the Xinzhuang-Luzhou line. The turn-out structure is the shape of a trumpet with its west

section more wide and its east section more narrow, of which its length is 125 m and width is 14.9
m~26.9 m. The excavation depth of the turn-out structure is 39.5 m~41.5 m. In order to support the
sides of the excavation, a 2 m-thick, 63 m-deep diaphragm wall was constructed around the site
perimeter and a 13-layer temporary H-shaped steel strut was used as a retaining structure. Due to the

lack of an impermeable soil layer lying beneath the foundation excavation face, the safety factor of
the final excavation face did not satisfy Civil Engineering Design Manual (CEDM) specifications.
So plugged grout and dewatering through the application of a Jingmei Gravel Layer was applied
as an auxiliary method to stabilize the structure foundation excavation to avoid leakage problems

on the final excavation face. The auxiliary method not only avoided leakage problems but also
decreased the need for water to be pumped out of the Jingmei Gravel Layer, it also assisted with the
problem of up-lift of the final excavation face.
This article introduces the design and construction procedure of plugged grout and dewatering

in the Jingmei Gravel Layer in the turnout structure of section contract CK570C of the Taipei MRT.
Keywords: CK570C Lot, Jingmei Gravel Layer, Plugged Grout, Dewater