Proceedings-DFI/EFFC 11th International Conference on Piling and Deep Foundations, 2014, Stockholm, Sweden, (DFI)
Experiences of High Strain Dynamics Pile Testing (HSDPT) in Accordance with EC7 in Sweden
Mattias Grävare, Ingemar Hermansson, Thomas Bjerendal and Carl-John Grävare, Pålanalys i Göteborg AB, Sweden
High strain dynamic pile tests (HSDPT) on driven piles have been carried out on a routine basis in Sweden for more than 30 years. The Swedish Commission on Pile research established, in the early 1980s, safety factors based on the percentage of piles tested. The safety factors could then be reduced, creating economic incentives for the contractor to carry out testing. Energy formulas adopted by our neighbour countries, Norway and Denmark, were not accepted in Sweden as a reliable method since the dynamic testing method was considered to be a more scientific and reliable method. It has become almost the only in-situ method used to verify geotechnical bearing capacity on driven piles. The typical Swedish geology of soft soils overlaying very hard strata makes it possible to verify high design loads, typically 20 kN per cm2 of pile cross sectional area for steel piles and 1,5 kN per cm2 for concrete piles. Conventionally a certain percentage of the piles have been tested in Sweden. The EC7, on the other hand states a number of piles to be tested, regardless of the total number of piles. The Swedish NA (National Annex) states a maximum distance between tested piles, which results in better distribution of the test piles over the foundation. For shaft-bearing piles in soft clays, dynamic pile tests have to be correlated by static load tests.
|article #1901; publication #100 (IC-2014)|