Date of Award

Spring 2002

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Computational Analysis and Modeling

First Advisor

David E. Hall

Abstract

Thin-walled plastic pipe liners are routinely used to rehabilitate structurally sound host pipes that have lost their hydraulic integrity. Such liners are often installed below the water table and are consequently subjected to external hydrostatic pressure which may lead to creep-induced radial deflections and eventual collapse of the liner within the host pipe. Most of the current liner design model is based on the extension of short-term model to a long-term buckling liner design method. The objective of this thesis is to examine and provide a correction factor C* to allow short-term liner buckling models to be more accurately used in the prediction of long-term liner lifetime.

The long-term liner buckling models considered in this research include ASTM F1216, simple power law models, and models given by Li, Cohen, Straughan, Falter, and Zhao. And ASTM, Straughan, Falter and McAlpine's model are very similar. They all include the coefficient a and exponent m which account for the influence of host-pipe constrain and imperfections. The comparison between those design models and experimental data sets in Trenchless Technology Center had been performed by the author in 1999. In this research a new design model which considered the C* as a function of linear and quadratic combinations of liner geometry, material properties, ground water pressure and a correction factor C* will be presented. A simplified design approach which only considers the effect of creep constants and ground water pressure will also be presented in this research. These models are show good agreement to the experimental data and finite analysis results. In general, the C* value was seen to be almost greater than 1.0, with C* equal to 1.3 for a polyester material tested at the TTC when a 50 years is desired. And the simplify design model is proposed as a new design model for tight fitting sewer rehabilitation liners. The ASTM model design approach, which uses 1/2 of elastic modulus, is not a good design methodology in the liner design.

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