ESTIMATION OF TOE LOAD-SETTLEMENT RELATION OF NON-DISPLACEMENT PILES BASED ON BACK-ANALYSIS OF IN-SITU TESTS

HIROAKI NAGAOKA , MASAHIRO YAMAZAKI , YING ZHANG and TAKESHI OKAMURA

ABSTRACT: In this paper, a new estimation method is presented for the toe bearing behavior of non-displacement piles embedded into bearing strata of sand. The method is developed by numerical experiments. First, a new in-situ test is proposed whose results can identify five parameters of a bearing stratum uniquely. These are parameters of the stress- strain relations of sand and coefficient of earth pressure at rest. In the in-situ test, a cylinder of, for example, 10 cm in diameter is embedded into the bearing stratum. The measured results are a load-settlement relation at the end of the cylinder and a friction-settlement relation on the surface of the cylinder. These relations are back-analyzed, using elastic-plastic finite element method and neural network, and the parameters are identified. Then using the identified parameters, the toe bearing behavior of a pile is estimated by the elastic-plastic finite element method. The estimation method can be applied to piles embedded into over-consolidated sand as well as normally consolidated sand.

 Key words: (bearing capacity of pile toe), (coefficient of earth pressure at rest), (ground parameter identification), m- situ test, (non-displacement pile), over-consolidation, pile, sandy soil, stress-strain curve, vertical load (IGC: E4/E13)