Cured-In-Place Plastic (CIPP) pipe liners have recently been employed to rehabilitate deteriorated sewer lines. Such liners are often installed below the water table and are consequently subjected to external pressure which may lead to creep-induced buckling of the liner within the host pipe. Insufficient understanding of this buckling phenomenon is regarded as a limitation of the technology and a barrier to more cost effective sewer rehabilitation. To address this problem, coupled experimental and analytical research programs will be undertaken. The experimental program will involve room temperature and elevated temperature material characterization tests of liner materials as well as creep-buckling tests of liners at these same temperatures. The softening of this material with increasing temperature will be used to establish a relationship between time and temperature such that tests performed on convenient time scales can be extended to decades. The analytical program will examine closed form solutions to the buckling problem and will involve an extensive amount of finite element and statistical modeling of liner buckling. The statistical variation of liner buckling times as a function of the external pressure and liner/host pipe geometry parameters will be assessed to determine the probability that a liner system will survive for the desired design life. This research program will establish a new methodology for the long-term testing of plastic sewer rehabilitation liners and will highlight the factors which must be considered to develop a physically based model to predict buckling of CIPP liners over a 50+ year service period. ***
