Analysis of Bearing Characteristic of Drilling Expanded Bottom Cast-in-situ Piles

To study the bearing characteristic of drilling expanded bottom cast-in-situ pile, static load tests of two expanded bottom bored piles of different shape and one equal diameter pile were conducted, as well as pile stress tests of the expanded bottom bored piles. Test and data analysis results show that the influence of sediment and soil softening on the bearing capacity of expanded bottom pile is relatively sensitive. In addition to directly affecting the pile end resistance, it will also produce the weakening effect of pile side friction resistance. The shape of the enlarged head affects the slag removal effect at the bottom of the hole, and the high pressure grouting at the bottom of the pile can eliminate or partially eliminate the influence of the sediment. The development value of the pile side friction resistance of the same soil layer of different test piles is not fixed. Affected by the diameter change of the expanded bottom pile, the pile side friction resistance of the same soil layer of the same test pile within the range of 3 m above the diameter change is 15%~40%, lower than the value of the pile side friction within the range of 3 m above the diameter change. The test results can provide reference for the design and construction of expanded bottom piles.