Case Studies # 2001 Munich
When starting with the application of buried thermoplastics pipes in the fifties, Wavin started to gain a lot of experimental experience with these pipes, which later formed a solid base for the correct application of thermoplastics pipes. In analogy, a lot of experimental experience is gained now with buried manholes and inspection chambers as well, starting some 8 years ago with systematic research. Although also sophisticated numerical calculation methods are utilized during the product design phase, still the experimental experience is found to be paramount compared to calculations. As with pipes, a true description of product and soil performance is needed as well as the way the chambers are installed in the ground. Effects like workmanship, soil types, ground-water, compaction and surface loading are difficult to simulate in calculations in a correct way, and when tried, they shall always be verified with practical experiments. Extensive, full-scale field trials were carried out and are still partly in progress, in order to build confidence with manholes and to define their limitations in use. Trials were carried out in France, Germany, Scandinavia and Poland. Trials were performed with different types of manholes, varying from rather rigid to very flexible, from small (315 mm) to big (1250 mm). From these trials a lot of information has become available and resulted in a confident use of plastics manholes and chambers. This paper discusses the loading types, like soil type, settlement and surface loading and other phenomena that were encountered during the field tests, and give guidance to the application of buried manholes. It is shown that plastic manholes, when well designed, add significant value to the achievement of a sustainable sewer system.