Page 388 - Trenchless Technology Piping Installation and Inspection

338 Cha pte r Ei g h t

8.5.2 Materials

Pipe
Pipe used in this method includes an external steel casing pipe and
may include an interior carrier pipe.

Pipe Dimensions and Requirements
Refer to pipe, casing, and spacer requirements for the horizontal
auger-boring method mentioned in Sec. 8.3.2.

8.5.3 Construction
Equipment
Equipment used for this method varies greatly. However, the basic
operations of hammering the pipe into position and removing the
excess soil are essential. Please refer to the specific operator’s manual
for more information.

Method

1. Each pipe section must be rammed forward as the excavation
progresses in such a way to provide complete and adequate
ground support at all times. Lubrication must be applied
to the external surface of the pipe to reduce skin friction.
A hammer frame must be positioned to develop a uniform
distribution of ramming forces around the periphery of the
pipe. Special care must be taken by the contractor to ensure
that the launch seal is properly designed and constructed.
Special care must be taken when setting the pipe guard rails
in the pit to ensure a correct alignment.
2. In open-end ramming, either a prefabricated soil-cutting
shield must be attached to the front of the casing pipe leading
edge, or a casing band must be welded around the outside or
inside edge of the pipe. In closed-end ramming, a cone-
shaped attachment must be welded or threaded to the front
of the casing pipe.
3. Whenever possible, the casing pipe must be driven in a con-
tinuous, single run. If space is limited, the job can be com-
pleted in a series of short ramming sections. Length of pipe
sections must be selected based on available space for an
insertion pit setup. Casing pipe section length between 20 and
40 ft is frequently selected. Section lengths between 10 and 60
ft can be allowed considering the availability of pit space.
4. The contractor must dispose of all excavated material from
the pipe ramming and access pit construction operations