Ratcheting analysis of 'pipe - freezing soil' interaction

摘要

Flotation of buried pipelines at cyclic freezing and thawing of the surrounding soil prevents normal operation of pipelines and may lead to their fracture. This problem is especially relevant for buried pipelines in freezing soils with high water content. The traditional explanation for this emergence of the phenomenon is the Archimedean force (even the term "flotation" indicates this). At the same time, a similar phenomenon known as "strain accumulation" or "ratcheting" is well known in high-temperature engineering. This phenomenon consists in the increase of a structure displacements with the number of loading cycles. Under certain conditions, such accumulation can become stable (the same in successive cycles) and lead to large accumulated displacements after a corresponding number of cycles. The study considers an attempt of applying the methods developed for analyzing displacement accumulation in high-temperature structures of power engineering industry, to the problem of pipeline flotation. It shows that such a mechanism (ratcheting) can play an important role in this task, and the choice of ways to counteract the flotation essentially depends on the process mechanism.