The design and performance of pressure pipe liners under static and cyclic loading

Cured-in-place pipe (CIPP), is a widely used trenchless technology. Based on the current liner design method, American Society for Testing and Materials (ASTM) F2207-02, several aspects are studied for the effect on estimating the long-term performance of the liners. While estimating the liner burst pressure, the effect from host pipe material properties, liner material properties, defect geometry, liner creep properties and loading condition should be considered. The burst pressure calculated based on the existing method is overestimated and this allows an increased risk of structural failure before the expected design life is reached. Compared with cast-iron, a PVC host pipe provides less constraint for the liner and causes a lower liner burst pressure. The existing method is safe to calculate the liner burst pressure when the defect size is at the high end of the range of defect sizes in comparison with the host pipe size. When the defect size decreases, the estimate becomes less safe. To maintain the same safety factor, a correction should be applied to reduce the estimated liner burst pressure. To estimate the liner burst pressure for defect shapes other than square and circular, the defect area should be measured and transformed to a square shape with same area. Based on the length of the square, the ASTM method can be used to calculate the liner burst pressure. It is also recommended to use different correction factors based on the extension direction of the defect. The creep property of the liner is not an ignorable factor. The displacement could increase about 100% due to the creep effect. A cyclic loading condition shows a noticeable effect on the development of displacement and strain. The strain development shows that a liner\u27s Young\u27s Modulus gradually decreases under a cyclic loading condition. This means that a liner could fail under a cyclic loading condition at a lower pressure level. Based on this research, correction factors, according to each of the different aspects of liner behavior outlined above, are recommended for estimating an appropriate liner burst pressure. Recommendations for further research are also provided