Model tests on shaft capacity properties of bottom uplift pile

The bottom uplift pile is a new type uplift pile for solving the problems of concrete cracks in pile shaft and the effect of interaction between strata and pile head. The unbonded steel strand with both ends anchored in the toe of concrete pile and slab of underground structure respectively is adopted to transmit the uplift load into pile bottom. There are some differences between tensile pile and bottom uplift pile in shaft capacity properties. The model pile tests are adopted to investigate the characteristics of the ultimate shaft capacity, shaft axial force and shaft friction of tensile pile and bottom uplift pile. The effects of Possion’s ratio are discussed for the above two types of piles. For the method calculating the shaft capacity of tensile pile, pile stiffness coefficient is used to determine the tension coefficient of bottom uplift pile. The method for shaft capacity is proposed and validated for bottom uplift pile.