Pipeline Rehab: Underground Options

by James C. Thomson, Senior Consultant; Jason Consultants S.A., Geneva,


Serial Information: Civil Engineering—ASCE, 1991, Vol. 61, Issue 5, Pg. 64-66


Document Type: Feature article

Abstract:

While simply digging up old pipes and replacing them is sometimes still best, other alternatives can give long life while easing the strain on the community. Trenchless methods for on-line sewer replacement can be classified as bursting or excavation replacement. Bursting involves hydraulic or pneumatic devices that apply radial forces to the old pipe, shattering it and forcing the fragments into the surrounding soil. At the same time, the new pipe is pulled up or pushed in behind the bursting device; these systems can work from existing manholes. Excavation replacement is done by remote-controlled microtunneling machines that crush rock. As the machine advances through the old sewer, the new pipes are jacked in by the excavating head to form the new line. Renovation techniques, which improve a pipe's performance and working life rather than replacing it outright, include slip lining, modified slip lining and spraying. Slip lining involves installation by pulling or pushing a new pipe inside the old one. This method reduces cross-sectional area and flow capacity. Modified slip-lining systems aim to minimize loss of cross-sectional area by inserting a tube into the existing pipe, then hardening or reshaping the tube to fit the inside of the existing pipe. A new method, structural spraying, strengthens the pipe with a resin and hardener and does not close off laterals, as sliplining methods do.

Subject Headings: Pipes | Linings | Excavation | Tubes (structure) | Structural strength | Sewers | Pipe failures

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