A Comparison of the Results of the Numerical Analysis and the Physical Behavior of a Pipe Buried in Reactive Clay

Buried water and gas pipe systems form part of critical infrastructure providing essential services to the community. In many global population centres including in Australia, this vital infrastructure has been installed several decades ago, and dealing with frequent pipe failures become a major problem. There are clear evidences that pipe failures significantly depend on pipe strains induced by seasonal temperature and moisture changes. The past pipe failure data also indicate that the pipe failure increases when soils are more reactive. However, not much research work has been performed in order to understand the possible failure mechanisms of pipe buried in reactive soils. Therefore, in this study, the behaviour of a two meter long polyethylene pipe, which was buried in a box filled with reactive clay, was studied while the clay was subjected to wetting by supplying water to the bottom of the box. With soil wetting, it was observed that the soil swelled and the pipe deflected upwards. A simplified numerical analysis was then conducted on the pipe buried in the soil box using laboratory measured soil and pipe properties. The measured deflected shape of the pipe reasonably agrees with the shape obtained numerically assuming pinned end conditions of the pipe.