Evaluation of bearing capacity of taper type pile foundation taking care of soil compressibility and its application to the performance based design

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An improved effect of vertical bearing capacity of taper pile expanded in sandy ground is investigated based on the experimental results from a series of the model pile load tests and theoretical considerations. The important results obtained are summarized as follows :1)An apparatus mainly focused on the function of the expanded system of the pile was developed,. The way of changes in horizontal stresses of a model ground surrounding the pile due to its expansion is clarified with reference to the degree of the expansion.2)An improved effect of the skin friction due to the expansion was clarified based on the experimental data. In addition, a simple idea to evaluate the improved pile skin friction is introduced in this study. Its applicability is verified by the experimental data. It can be found from the experimental results that the pile with an expanded function in practice is environmentally effective to improve the pile skin friction.3)An simple estimating method for predicting the vertical bearing capacity of taper type pile was proposed based on the extended cavity expansion theory. It is characterized that the model can evaluate the vertical bearing capacity of taper type pile with different taper angles.4)It was confirmed that the model can also reflect the effect of the soil compressibility on the bearing capacity, by comparing the results from the model pile load tests.5)The rest works were pointed out for introducing the technical outcomes in this study into the performance based design of pile foundation rationally.