MODEL TESTS ON NEGATIVE SKIN FRICTION ON PILES CONSIDERING SEQUENCE LOADED ON PILE HEAD AND SURCHARGE AROUND PILES

As for piles under negative skin friction，there exists a sequence loaded on pile head and surcharge around piles． However，the influence of the loaded sequence on negative skin friction is less studied． Aiming at researching the influence of the loaded sequence，the indoor model tests for negative skin friction on single pile in sand were carried out． The axial force of pile shaft，settlement of pile top and each soil layer were measured． The results showed that the influences of the loaded sequence were obvious on the negative skin friction of the pile in sand． When the surcharge around piles were loaded first，the neutral plane were closer to piles tips． Settlement of piles loaded on surcharge around piles first were significantly smaller than that of piles loaded on the tops first． The pile head settlements under the action of surcharge load were basically identical with the different loaded sequence，and the increase amplitudes of pile head settlements slowed down gradually with the increasing of surcharge load around piles．