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An Empirical-Theoretical Calculation Method and Full-Scale Verification Test for the Ultimate Bearing Capacity of an Expanded Pedestal Uplift Pile
(1 Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092; 2 Shanghai Geo-anchor Co. Ltd., Shanghai 200092)
Abstract Considering the influences of such factors as soil mechanical characteristics, pile material properties, pile length and pile diameter (including the expanded pedestal diameter), depth of the pile top, and unloading and loading around the pile top and pile group effect, combined with engineering practices, an empirical-theoretical calculation method for the ultimate bearing capacity of an expanded pedestal uplift pile is proposed in this paper. Based on different positions of the failure surface of the expanded pedestal uplift pile, the failure mode of the expanded pedestal uplift pile is divided into three types: entire shearing failure from the failure surface extending to the ground surface, local shearing failure of the failure surface between the ground surface and borehole-expanded section, and punching shear failure of the failure surface near the borehole-expanded section. An ultimate equilibrium state equation under the entire shearing failure mode is derived. According to the axial symmetry conditions of the expanded pedestal uplift pile and the mechanical characteristics of the lower soil tensile strength, a differential cylinder numerical solution is given regarding the entire failure surface. By using the empirical method to estimate the end resistances under the local shearing failure mode or punching shear failure mode, the calculating procedure and method for the ultimate bearing capacity of the expanded pedestal uplift pile in any soil layer is put forward. Finally, the reliability and accuracy of the calculating method is verified through a comparison between the calculated ultimate bearing capacity and the measured one in a full-scale test.
Abstract：
Considering the influences of such factors as soil mechanical characteristics, pile material properties, pile length and pile diameter (including the expanded pedestal diameter), depth of the pile top, and unloading and loading around the pile top and pile group effect, combined with engineering practices, an empirical-theoretical calculation method for the ultimate bearing capacity of an expanded pedestal uplift pile is proposed in this paper. Based on different positions of the failure surface of the expanded pedestal uplift pile, the failure mode of the expanded pedestal uplift pile is divided into three types: entire shearing failure from the failure surface extending to the ground surface, local shearing failure of the failure surface between the ground surface and borehole-expanded section, and punching shear failure of the failure surface near the borehole-expanded section. An ultimate equilibrium state equation under the entire shearing failure mode is derived. According to the axial symmetry conditions of the expanded pedestal uplift pile and the mechanical characteristics of the lower soil tensile strength, a differential cylinder numerical solution is given regarding the entire failure surface. By using the empirical method to estimate the end resistances under the local shearing failure mode or punching shear failure mode, the calculating procedure and method for the ultimate bearing capacity of the expanded pedestal uplift pile in any soil layer is put forward. Finally, the reliability and accuracy of the calculating method is verified through a comparison between the calculated ultimate bearing capacity and the measured one in a full-scale test.
ZHANG Ji-Hong-1,
2 ,
Zhu-He-Hua-1
.An Empirical-Theoretical Calculation Method and Full-Scale Verification Test for the Ultimate Bearing Capacity of an Expanded Pedestal Uplift Pile[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(6): 50-57
2014, Vol. 51 