Frans Alfernik - Wavin M&T (Netherlands) This paper describes the design of buried flexible pipes in general, with the emphasis on thermoplastics pipes. The purpose of any design method is to predict the likelihood to exceed a limit state condition of the structure. Therefore the paper first describes the limit state conditions, after which the research project carried out is shortly described and the final results reported. The paper focuses on the performance of gravity pipes. Extensive field trials have been performed in a project sponsored by TEPPFA and APME, to obtain well documented information about the behaviour of buried thermoplastics pipes. This information is of vital importance to obtain a workable design method for buried pipes. Tests were carried out using different pipe materials (PVC, PE, Steel), different pipe stiffness, buried at depths varying between 1.15 and 3 metres, using clay as well as sand as sidefill, and by installing them in a compacted as well as in a dumped way. Pipe deflection and strain measurements were carried out, when loading the pipes by soil, traffic and internal hydrostatic pressure. European design experts were put to work with the soil and pipe parameters, and asked to carry out the design using their own or their national design method. Afterwards, they were provided with the results of the measurements carried out on the pipe as well as on the soil, allowing them to evaluate their design. Then in December 1997 a workshop took place with those experts to discuss the results and with the intention to obtain a good basis for establishing an unified design method for all buried pipes, and by assisting current CEN work on the same subject. The results showed that consistency between installation and design practice is one of the major factors to be considered. Based on the results as found in the field studies, a design approach which safely predicts the behavious of buried pipes is recommended. Download the complete story as a Word Document BACK TO