Research On The Three-axis Borehole Cast-in-place Pile

The three-axis borehole cast-in-place pile is a new foundation pit support, which is developed on the basis of the traditional borehole cast-in-place pile by Southern Civil Engineering Consulting Co., Ltd. Compared with the traditional borehole cast-in-place pile, the three-axis borehole cast-in-place pile which has same construction technology and cost, has a higher cross-section bearing capacity and bending stiffness and is more suitable for deep foundation pit support.In this paper, the borehole cast-in-place pile was studied at home and abroad. Most of the domestic studies focus on construction technology and technical measures, whose design and calculation method is seldom researched. Currently, there is no unified design and calculation method in China.The cross-section bearing capacity formula and the bending stiffness formula of the three-axis borehole cast-in-place pile are derived from the theory of the reinforced concrete and the extensive studies. In this pape, 4 models of the three-axis borehole cast-in-place pile are tested Through the comparison between the experimental data and the oretical data, we know that the theoretical formula is reasonable, and can serve as the cross-section designing formula and the checking formula.Finally with the theoretical formula established in this paper, a three-axis borehole cast-in-place pile is calculated. After comparing the calculation results, we know that the cross-section bearing capacity of the three-axis borehole cast-in-place pile can be 50% higher than the traditional one and the cross-section bearing capacity bending stiffness is also 100% higher with the same budget. Under the same load, the reinforcement needed in three-axis borehole cast-in-place pile can be reduced by half of those in the diaphragm wall, but the ross-section bearing capacity bending stiffness can be enforced 5 times stronger. Therefore, the three-axis borehole cast-in-place pile which is more advanced than the traditional borehole cast-in-place pile should be applied and promoted.