Study on Mechanical Properties of Composite Foundation with Rigid Pile Based on the Cushion and Strength Adjustor Control

Abstract

Settlement of the pile ends in end-bearing rigid pile composite foundations is generally minimal, so only relying on the cushion to coordinate the pile soil deformation may result in insufficient deformation adjustment capacity. Using a deformation adjustor with a specific stiffness on the top of the pile is a method to coordinate pile–soil deformation, and the stiffness value of the deformation adjustor depends on the accurate calculation of soil deformation; however, the calculation of soil deformation is not mature at present. A new deformation adjustor based on strengths used in composite foundations is proposed, in which foam slabs with different yield strengths are placed on the top of the pile to coordinate the pile–soil deformation. Five tests are used to study the mechanical and deformation properties of a composite foundation with a foam slab. The test results show that when the stress at the top of the pile is less than the yield strength of the foam slab, the coordination of the pile–soil deformation mainly depends on the cushion. When the stress of a rigid pile exceeds the yield strength of foam concrete, the foam slab begins to yield and coordinate the deformation of pile and soil, and the settlement coordination ability of a rigid pile composite foundation with a foam slab is significantly improved. Finally, an engineering case is used to simulate the pile–soil stress sharing when the actual settlement is greater than the calculated settlement. The case analysis shows that the pile-top stress can be well controlled by the successive yielding of foam concrete slabs of different strengths, which reduces the influence of settlement error on the pile–soil stress sharing, and further promotes the engineering application of end-bearing rigid pile composite foundations.