Published Online: 7 September 2005
Page Count: 8
Chairman and Professor, West Virginia University, Morgantown, WV
Graduate Research Assistant, West Virginia University, Morgantown, WV
(Received 2 June 2003; accepted 23 March 2005)
Due to increasing costs and inconveniences in replacing deteriorated sewer pipelines by conventional excavation methods, the trenchless or “no-dig” technology is being used extensively. In this manuscript, a testing method is proposed to determine the long-term creep behavior of encased polymer and felt-reinforced polymer liners used in sewer rehabilitation. Long-term tests are conducted on liner samples encased in steel pipes, installed by the industries participating in the research project. The thicknesses of the polymer liners are selected according to the typical use of each product in the field. Three samples each of five liner materials are tested under constant external hydrostatic pressure to find their long-term structural properties. A pressure regulator, pressure transducer, and several pressure gages at different points in the water line are used to maintain constant hydraulic pressure in the gap between the steel host and the polymer liner. A method is proposed for sealing the ends of the encased liner samples for testing. The long-term creep data are collected with strain gages bonded along the inner circumference of the liner and connected to a data acquisition system (DAS). A data reduction method is proposed to separate the membrane and bending strains in order to compute the creep compliance. The temperature of the liners is monitored continuously with the use of a thermocouple. The strain data collected from the DAS are compensated for differences in temperature throughout the period of testing, initial deformation, and coefficient of thermal expansion. Several viscoelastic models are investigated in order to fit the data. The data are used to predict the long-term modulus used in the design of trenchless rehabilitation projects.
Paper ID: JTE11982