Stresses Development in Inhomogeneously Leached Asbestos Cement Pipes

This paper uses finite element modeling (FEM) to examine the developed stresses in a buried asbestos cement pipe that experienced leaching for pipe replacement assessment. It is necessary to prioritize at high failure-risk pipes in light of the fact that not all pipes can be replaced at once. Different parameters are considered when evaluating pipes’ condition and longevity. A major consideration is the pipe’s structural ability to withstand different loads, both from the inside and the outside. Currently, when a pipe is diagnosed with leaching at a certain depth, the entire pipe is considered isotopically leached with the same depth, i.e., the entire pipe thickness is reduced. In this way, the longevity and operating limits of the pipe can be safely estimated. Aside from providing a safe and conservative estimate, this method is also practical and simple. Nevertheless, it is possible to gain a better understanding of the developed stresses by performing a FEM analysis of the pipe in a localized manner. In this manner, we can identify the distribution of stresses along the pipe section, the maximum developed stress that might lead to failure, and the critical factors involved with it. This research aims to determine if the current method undervalues or overestimates the pipe’s actual strength, longevity, and operation capabilities. The pipe was modeled as a constructive solid geometry in COMSOL software. The pipe model was subjected to a variety of forces, including loads from the soil above, normal forces from below, and water pressure from within. This study tests leaching in a long band shape for the entire length of the pipe, hereby referred to as band-leaching. In order to determine the failure factors for band-leach characteristics, different combinations of width, depth, and location are tested, with each combination resulting in different stresses and deformations.