Abstract EN:

As a consequence of their aging, the performance of buried pipes has become a major concern for the urban sewer systems managers. Improvement of both the pipe design and its installation conditions or a more efficient management requires first a comprehension of phenomena that lead to pipe deterioration. This research starts a new long-term and multidisciplinary topic where the study of the structural pipe degradation in relation with soil condition represents only one part of the whole extent. Within this context, our approach consists in first identifying such phenomena, then describing their effects on sewers. This PhD thesis is composed of three different parts. In the first part, a statistical analysis of failures affecting the Greater Lyon sewer network and the factors that are likely to make them appear is achieved in order to determine in what circumstances these failures occur. It is then possible to identify some of the mechanical processes that may generate the pipe deficiencies. It appears that the phenomena identified as having a major influence on the pipe behaviour are completely ignored by the current design standards. The second part is dedicated to the experimental characterization, via laboratory tests, of the mechanical behaviour of the most unknown part of the sewer pipe: the joint. A rheological model of its behaviour under three types of loading is developed so that it can be easily adapted to all kinds of joint with rubber gaskets. The last part regards a numerical 3D modelling of a trench and a pipe which includes all the major parameters having a significant influence on the pipe behaviour. A numerical representation of the joint is based on the lab test results, while the rest of the model is validated with the results from the literature. This numerical modelling is then used to investigate the influence of the soil variability within the trench, particularly focusing on the longitudinal pipe behaviour.