Reliability Estimation of Buried Pipelines Using First-Order Reliability Method

Corrugated polyethylene (PE) pipes are used widely for a variety of applications. These pipes provide substantial benefits over concrete, metal, and other traditional pipes in terms of their ability to resist environmental stresses from chemical and biological agents. Furthermore, they are easy to install, tough in the field, durable in service, and environmentally benign. In this article, the limit state function (LSF) is formulated in accordance with conventional design method. The first-order reliability method (FORM) is utilized to extract useful technical information in carrying out the effective design procedure for corrugated PE pipe. Using the three design criteria and failure probability, the methodology for reliability estimation of corrugated PE pipe is investigated. The effects of varying design parameters on failure probability are systematically studied. Of the three design criteria, it is found that the bending stress design criterion shows the smallest failure probability, and the deflection design criterion shows the largest failure probability for varying design parameters. It is recognized that the failure probability increases with an increase in the coefficient of variation (COV) of random variables. It is also noted that such design parameters as burial depth, modulus of soil reaction, outside diameter, pipe stiffness, soil density, and distance to neutral surface must be selected properly to achieve the required safety level.