The city life in urban area is supported by lifeline such
as sewerage system, water supply system, city gas, electricity

and electrical communication, and most of them consist of
buried pipe in the ground.

The burial methods for these lifelines include the open-cut

method and the trenchless method.

The open-cut method's procedure is as follows and this method
has problems like traffic congestion, street pavement damage,
cost of surface damage, etc. Then, it is often difficult to
be adopted in overcrowded city.

(1) The ground surface is cut open.
(2) Ready-made pipes are arranged on the bottom of the
trench.
(3) The trench is buried back.

Open-cut Pipejacking Method

Fig.1 Comparison of Pipe Construction Method


Trenchless method includes the shield method and the
pipejacking method, and these methods need excavating
less area of the ground surface compared to the open cut
method. Therefore, trenchless method is excellent concerning
the urban environment measures such as: reduction of the
area used for the construction; reduction of the public
nuisance caused by the construction including noises,
vibration, dusts; and reduction of influence on traffic
and citizens' living.

(1) A shield machine excavates the ground in front of it.
(2) Segments are erected in the shield machine.
(3) The tunnel interior is completed with lining.

(1) A starting shaft and an arrival shaft are provided
respectively at both end of a designed pipeline
(2) A pipejacking machine is jacked into the ground by
a hydraulic jack from the starting shaft which has
a jacking equipment.
(3) Jackingpipes are added and connected one after another
at the rear end of the jackingpipes and the series of
pipes are jacked.
(4) Thereby, the tunneling machine is delivered to the
arrival shaft, and a conduit is constructed between
the starting shaft and the arrival shaft.


Fig.2 Configuration of Pipejacking


Classification of pipejacking method is shown in Fig.3.
The pipejacking method is classified into:

(1) Large and medium diameter pipejacking method for a
nominal diameter of 800mm or larger,
(2) Microtunnelling for a nominal diameter of 700mm or
smaller,
(3) Pipejacking for lateral pipes, and 
(4) Pipe-replacement method.

The large and medium diameter pipejacking is classified into
earth-pressure-balance type, and the soft slurry type depending
on the cutting face supporting method, the spoil transporting
method, etc.

Microtunnelling is classified into three methods depending on
the type of the jacking pipe used.  These are microtunnelling
for the concrete pipes, for the PVC pipes, and for the steel
casing pipes.

Fig.3 Classification of Pipejacking Method
(Detail of these methods will be explained in following Newsletter.)


With the expansion of the sewerage systems from the large
cities to rural small- and medium-sized cities, or from
main lines to sub-main lines and branch lines, various methods
have been developed in response to the social needs.
Today, diversification of uses is facilitated such as
establishment of the construction method for long lines and
sharply-curved lines, improvement of equipment and material,
automation of control and measurement.


This topic is provided in cooperation with
Japan Society for Trenchless Technology.