Buildings, Vol. 16, Pages 2767: Bearing Characteristics of Large-Diameter Pile Foundations Based on Loading Reaction Tests Using the Tension–Compression Anchor Method

Buildings, Vol. 16, Pages 2767: Bearing Characteristics of Large-Diameter Pile Foundations Based on Loading Reaction Tests Using the Tension–Compression Anchor Method

Buildings doi: 10.3390/buildings16142767

Authors:
Zhihui Zhang
Yifu Quan

To clarify the bearing characteristics and load transfer mechanisms of long large-diameter pile foundations in dense silty fine sand strata within the middle and lower reaches of the Yellow River, a graded tension–compression anchor reaction loading test method was devised and implemented using a field-configured apparatus. This approach enables graded static load testing on large-tonnage long bored cast-in-place piles. Then, the relative displacement and settlement between pile and soil under vertical cyclic loading were analyzed. Finally, numerical simulations were adopted to study the settlement behavior of pile tops and ends under cyclic loads representative of beam yard operational conditions (20 cycles). Results indicate that, under vertical loading, the shaft friction resistance and tip resistance of large-diameter long bored cast-in-place piles are not mobilized simultaneously, but sequentially. The degree of shaft friction is related to the magnitude of pile top loading, soil properties, burial depth, and construction methods. The soil between piles generates vertical resistance to horizontal force-transfer rods, becoming part of the pile foundation’s bearing capacity and sharing the load. Moreover, in dense silty fine sand strata, long large-diameter pile foundations exhibit pure friction pile behavior. When calculating the bearing capacity of such piles, parameters from geotechnical reports based on code-specified values should be multiplied with corresponding correction coefficients. In addition, the shaft friction resistance in dense silty fine sand layers remains under-mobilized. Limited loading–unloading cycles in permanent–temporary integrated beam yard operations do not induce significant deformation in pile foundations, indicating minimal impact on their bearing performance.