Experimental and Numerical Studies on Bearing Characteristics of Hexagonal-Section Composite Foundation Element

Hexagonal-section composite foundation is a new method of foundation reinforcement. The load-settlement characteristic and load-transfer mechanism play a critical role in the bearing capacity of pile composite foundation. The quantitative assessment of the hexagonal-section composite foundation element (Trilobal Pile for short) under vertical load was carried out through experimental and numerical studies. The variation rules and the influencing factors of stress and displacement of trilobal pile were compared and analyzed in ten model tests. And the numerical approach with trilobal pile (composite foundation) and equal diameter pile composite foundation were also conducted to simulate the loading process and the stress variation. The results show that the load-settlement curve of trilobal pile changed slowly and its ultimate bearing capacity was about 150 kN. Compared with the equal diameter pile, the ultimate bearing capacity of trilobal pile was increased by almost 275%, and the settlement was reduced by nearly 104.2%. The pile-soil stress ratio of trilobal pile was always greater than 1, and the maximum was about 7. And the axial force and lateral friction resistance of the trilobal pile changed abruptly at the variable cross section. The maximum axial force abrupt change rate of the trilobal pile was about 10%, and the abrupt change rate of the lateral frictional resistance of each test pile was about 65.2-82%. These results provide useful theoretical references for further development and optimization of the trilobal pile.