Page 66 - 捷運技術 第38期

60 洪顯宗 矢野勝也 推管工法特殊障礙處理─牽引工法

Special Treatment for Removing Obstructions in the Pipe Jacking Construction

- Pull Back Method
1
Sen-Drong Hung Katsuya Yano 2

Abstract

In urban areas the pipe jacking method is commonly used for small- and medium-sized tunnel
construction, such as construction of larger size electricity conduits, water pipes, and sewage pipes,
etc. In order to complete the pipe jacking construction smoothly, selecting a suitable machine

conforming to the geological conditions is the most important concern. However, in urban areas, no
matter whether the shield driving method or pipe jacking method is adopted, it often occurs that the
machine becomes stuck as the result of encountering unexpected obstructions, such as abandoned
construction objects, unusually big stones, withered pieces of wood, etc.

In a congested urban area, if the driving machine is stuck as the result of encountering
obstructions in the process of shield driving or pipe jacking and the obstructions can not be removed
from the inside of the tunnel, the most direct and fastest reinstatement method is to construct a
temporary shaft above or in front of the machine and then take out the obstruction(s) directly.

However, this recovery method is quite difficult. It is not even applicable if a temporary shaft cannot
be constructed due to topographic or geological limitations, such as traffic diversion, road width,
insufficient fenced area, and adjacent building safety, etc.
Theφ1650 mm sewage pipe jacking construction on Anhe Rd. Station of Xinyi MRT line's

CR580 project encountered the above-mentioned difficulties. They were solved by using the “pull
back method.”The method, applied in Taiwan for the first time, put simply, is to pull back the pipe
jacking machine with RC pipes having been installed in the work shaft behind it. Thanks to the
success of the method in pulling back the machines and sewage pipes for the first time in Taiwan,

it provides an additional option to the current method which is to remove obstructions only from
an excavated shaft. Of course, for the safety of adjacent buildings and roads, the method requires
deliberate advance planning and careful execution during construction. This article details the entire
process of the“pull back method” and to highlight particularly that the method is also applicable

on a large size shield tunnel.