Microtunneling with PVC Pipeby Mohammad Najafi, Louisiana Tech Univ, Ruston, United States,
Tom Iseley, Louisiana Tech Univ, Ruston, United States,
Hiroharu Nishida, Louisiana Tech Univ, Ruston, United States,
Document Type: Proceeding Paper
Abstract: PVC is a suitable and economical product for sewer system construction. However, in the past, utilization of PVC sewer pipe in microtunneling was impossible due to axial thrust load limitations and lack of a smooth joint compatible for microtunneling. In June 1992, a full-scale field test was conducted at Louisiana Tech University to determine capability of the LLB - Laying pipes of Low Bearing force - microtunneling propulsion system to install PVC sewer pipe in a range of soil conditions. In this method, a newly developed air-inflatable internal gripper system for microtunnel boring machines enables PVC or other flexible low strength pipes to be jacked directly. The primary thrust force of the microtunneling machine is transmitted through a temporary steel liner casing which runs inside the PVC pipe. The frictional resisting force is transmitted through the gripper mechanism, which binds the internal surface of the plastic pipe sections at designated intervals to the liner casing. With this new method, the jacking pipe experiences less axial compressive forces than with conventional methods of microtunneling. This allows microtunneling methods to utilize a variety of pipe materials which will enhance the cost effectiveness of microtunneling to open-trench construction. The results of this evaluation program showed that LLB microtunneling system is able to successfully install a low bearing capacity pipe, such as PVC sewer pipe, in a range of soil conditions.
Subject Headings: Pipelines | Microtunneling | Sewers | Construction equipment | Plastic pipes | Axial loads | Thrust | Field tests
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