Abstract
A series of full-scale in-situ pull-out tests has been carried out for cast-in-place concrete piles with one-belled or two-belled enlargements in order to investigate the characteristics of uplift resistance behavior of the piles with belled enlargements. In-situ pull-out tests for six belled piles and five multi-belled piles were performed at ten sites. The test piles were designed using steel-reinforced concrete structures to be able to reliably transfer the tensile force. A long H-section structural steel beam was inserted onto the pile toe with stud connectors arranged over the length of the H-section. All test piles were installed strain gauges at several sections along their depth to estimate the axial force. The results indicated that larger peripheral surface resisting stresses were exhibited by belled enlargements compared with the shafts embedded in almost identical soil layers. According to the test results, a design formula for estimating the peripheral surface resisting stress of the belled enlargement based on soil strength was shown.
