Zur inneren Standsicherheit eines Fangedamms

The inner stability of a coffer dam.

Based on the findings from geotechnical model tests, those sliding surfaces are identified, that occur related to the "inner" failure of the soil filling of a coffer dam. Herefrom, a new approach for the verification of the stability of the soil filling is derived. The idea of the development of the sliding surfaces in the ultimate limit state (and therefore also the verification procedure) diverges from the one described in the "Recommendations of the Committee for Waterfront Structures Harbours and Waterways" (EAU, 2004 [3]). If the approach presented in this paper will be accepted after discussion in professional circles, the design of coffer dams could be carried out in a different (and in most cases more cost-effective) way. For example, the downstream wall of the coffer dam could be designed for active earth pressure (according to the rules of the EAU, the 1,25-fold active earth pressure has to be used). If the "inner" failure of the soil filling is regarded as a sliding problem (taking in account the respective partial safety factors) the necessary width of cofferdam (to ensure the inner stability of the soil filling) calculated from the approach presented will be smaller compared to the width that is required in compliance with the EAU.