NUMERICAL ANALYSIS ON LOAD TRANSFER OF TENSILE PILES AND BOTTOM-UPLIFTED PILES

Based on the finite difference software FLAC3D, the numerical simulations of tensile piles and bottom-uplifted piles were conducted. Load-displacement curves, transfer of axial forces characteristics and distribution characteristics of lateral friction for the two types of piles were studied and compared respectively. The results showed that the ultimate bearing capacity of tensile piles was smaller than that of bottom-uplifted piles, and subjected to the same loads, the displacement of tensile piles was larger than that of bottom-uplifted piles. Load-displacement curves were mainly composed of broken lines. In the ultimate state, tensile or bottom-uplifted piles all failed suddenly. The axial forces in bottom-uplifted piles were transferred from the bottom to the top, and the axial forces in tensile piles were from the top to the bottom. For the two types of piles, the forms of axial forces along the shafts were opposite. With the growth of depth, the axial forces of tensile piles decreased, while that of bottom-uplifted piles increased. The lateral friction of tensile piles was similar to that of bottom-uplifted piles, which was smaller on the upper part of piles and larger on the middle and lower part of piles. Subjected to lesser loads, the upper lateral friction on bottom-uplifted piles was larger than that on tensile piles. Subjected to larger loads, except near pile tips, the lateral friction on the whole bottom-uplifted piles was larger than that of tensile piles. The curves on lateral friction and relative displacement between piles and soil were hyperbolic.