Pipejacking Good Practice Guidelines
The technique of
installing Subsurface Utility Networks in
In the right
geological conditions, microtunneling is and will be the preferred technique
of installing utilities at precise line and grade. The use and benefits of
microtunneling have been clearly established in
Microtunneling is an
effective means of installing utilities underground throughout first world
countries. The process is slowly developing acceptance world over. For
microtunneling to succeed, public agencies must begin to factor in the
environmental and social costs of installing utilities. They must resist the
urge to simply “do it the old-fashion way.” Microtunneling designs are
beginning to develop. Design documents will begin to become stronger and less
risky. To this end, engineers are needed to produce the design documents
necessary to produce competitive bids, at the lowest overall cost, and with
the lowest acceptable risk for the owner as well as the contractor.
To accomplish these
objectives, engineers must begin to fully understand the microtunneling
process. They must be able to establish the proper layouts of plan, profile,
and shaft locations. They must anticipate the potential problems and hazards
by documenting the geotechnical conditions, and establishing a geotechnical
baseline. Environmental considerations and permitting should be factored into
the design and cost estimates.
The design engineer
also must make sure the project can be accomplished or, more importantly,
recognize when conditions are not right for microtunneling. During
construction, the design engineer should review the contractor’s submittals,
making sure the client’s concerns are addressed and covered and to help
safeguard against the job going bad when an inexperienced contractor is on
board. And lastly, the design engineer should provide construction services
and inspection to verify that the intent of the design is realized and
assumptions made during design are confirmed.
What is the current
status of microtunneling operations in
Trenching is selected
by most contractors because they have the equipment available and personnel
trained to use it. Contractors are willing to undercut their costs in an
attempt to keep their existing equipment and personnel working. They are
unwilling to invest in new equipment or training of men to operate it.
For some projects,
special circumstances may exist that appear to favor microtunneling. These
special situations can included crossing under busy roads or streets,
wetlands or environmental sensitive sites, or sensitive buildings. Even here
however, few designs specify trenchless techniques. In most cases,
microtunneling is not considered an option because the cost is too high for
the isolated applications. It is cheaper for that contractor to dig an oversized
tunnel and then slipline the product pipe and backfill, unless he has already
invested in a microtunneling machine.
These guidelines are
an attempt to provide a reference tool to all the stakeholders facing the
requirements to develop or manage a Subsurface Utility Network where open
trenching is not possible or is expensive.
Dr. Niranjan Swarup
Indian Society for
counted from 15th Sept. 2006.