Zeitabhängigkeit von Stützspannungen sehr weicher Böden und ihre Relevanz bei der Bemessung stabilitätsgefährdeter Pfahlgründungen

Slender piles (micropiles) are a flexible and efficient foundation system and have therefore gained a wide field of application. In soft soils, however, the risk of pile buckling may limit the bearing capacity. Codes of practice existing for many decades are not supported by scientific research and have been called into question due to several cases of damage. Models that allow calculation of the buckling load of piles include several simplifications. The more accurate knowledge of the viscous lateral soil support, which influences the bearing capacity strongly, would allow to determine the security level of pile systems which are in danger of buckling more precisely. In this paper first results of small scaled loading tests that have been conducted within an ongoing research project, are presented. The test results reveal the main factors of influence. Based on these tendencies and on experiences gained from cone penetration tests in soft soils a basic model is outlined. This model should allow the prediction of the lateral soil support on pile shafts governed by the time dependent interaction.