Non-Pressure Pipes Systems # 2001 Munich
Two papers dealing with the intermediate results of the TEPPFA / APME project on design of thermoplastics pipes has been published at the 10th Plastics Pipes Conference in Gothenburg in 1998 by Alferink et al.1, 2 Meanwhile the study has been almost completed and the results discussed with several experts. Pipe installation turned out to be the most important parameter, and contrary to many design methods, burial depth and traffic load is not a real issue for buried flexible pipes. Based on these results, physics of pipes buried in soils were discussed. This was followed by some additional work, with the aim to further back up the results and try to find and propose improvements for the existing design approaches. The work consisted of a few extra field tests and several model tests. Some of these model tests have been performed first in 1999 and were discussed with the European design experts in a workshop. Based on these discussions more sophisticated tests have been performed and extensively documented. This paper shows part of the results and explains that the soil-pipe interaction process is primarily a volume process in case of flexible pipes. It illustrates the mistake that will be made when geometrical non-linearity is included in load steered methods for flexible pipes and the soil changes are neglected. Finally it proposes a model that can be applied to all existing theories and that will better reflect the actual performance of flexible pipes. Furthermore, it also gives some recommendations for the design of the more rigid pipes. Finally it advocates the use of simple transparent and understandable design methods, as these give by far the most reliable results.