Design method for geotextile tubes considering strain – Formulation and verification by laboratory tests using photogrammetry

Geotextile tubes are usually made of at least one layer of high-strength woven geotextiles. However, if only highly elastic materials are used, experience shows –comprehensibly – that the designed geometry and stresses, derived from standard formulations or special computer software, both using small strain membrane theory, essentially differ from reality. Therefore, an extended formulation, considering large strains, was developed within the scope of a study on the structural and hydraulic design of geosynthetic dewatering tubes at the University of Rostock. The solution was evaluated using a sensitivity analysis and verified in laboratory experiments, where small-scale tubes were surveyed using a low-budget, high-precision photogrammetric measurement technique. The new design method proved to produce good results. It should be used if the construction is indeed a long tube and if the limit strain of the geotextile tubes exceeds 10% strain. Finally, the results were compared with the existing methods for the structural design of geosynthetic applications, adding to the discussion about attenuation factors in geotextile tube dewatering projects. For short-term applications without refilling of the partly dewatered tubes, the product of attenuation and safety factors will usually not exceed a value of two.