Estimation of Toe Load-Settlement Relation of Non-Displacement Piles Based on Back-Analysis of In-Situ Tests

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.