MODEL TEST RESEARCH ON UPLIFTING BEARING CAPACITY OF STAR-SHAPED PILE

Star-shaped pile is a new type of special-section pile. It is formed by cutting five circular arcs in a circle pile. This paper aims to explore the uplifting bearing capacity of star-shaped piles. For comparison, the experimental tests on four single piles in dry sand by sand pourer construction are carried out in model tank of independent research and development. The four tested piles are the maximum ratio of perimeter and area of the five-star-shaped pile F₁,the maximum of the circumference of the five-star-shaped pile F₂,the round pile C₁ with the same section of F₂, and the round pile C₂ with the same cross-sectional area of F₂. Test results show:(1) The uplifting bearing capacity values of the pile F₁ and F₂ are basically the same. The maximum is the pile C₁. The minimum is the pile C₂. (2) The uplifting bearing capacity value of the pile C₁ is 1.73 times that of the pile F₁. The uplifting side resistance is weakened because of star-shaped section. (3) The side area of the pile C₂ is 0.66 times that of the pile F₂,but its uplifting bearing capacity is 0.8 times of the pile F₂. So it shows again that the star-shaped section weakens the uplifting side resistance. However, the uplifting bearing capacity value of the pile F₂ is 1.25 times that of the pile C₂,which shows that the circular section changing into the star-shaped section can improve the uplifting bearing capacity to some extent.(4) The distribution between uplifting side friction and displacement is hyperbolic. The side limiting friction is reached only by a little displacement.