Microtunneling & 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.
Prof. Niranjan Swarup
Indian Society for Trenchless Technology
counted from 15th Sept. 2006.