A case study on the bearing characteristics of a bottom uplift pile in a layered foundation

Abstract

The bottom uplift pile, which has been applied in practical projects, has the following advantages: the pile body is not easy to crack, good bearing characteristics, and small displacement of the pile top. Based on the bearing capacity test of foundation piles in the third stage expansion project of Lanzhou Zhongchuan International Airport, the upper part pile of the self-balancing test method was used to simulate the bottom uplift pile, and the anchor piles in the anchor pile method were regarded as normal uplift piles. The bearing characteristics of the bottom uplift pile in a layered foundation were studied by comparing these two kinds of piles. The results show that under the same displacement of the pile top, the ultimate uplift bearing capacity of the bottom uplift pile can be more than twice that of the normal uplift pile because of the fully exerted frictional resistance of the soil at the bottom of the pile, the Poisson effect of the pile body and the avoidance of the influence of pile body deformation on the pile top displacement. The maximum axial force of the bottom uplift pile appears at the bottom of the pile and gradually decreases from the bottom to the top, which is opposite to that of the normal uplift pile. The properties and thickness of the soil layers around the pile have a great influence on the distribution curves of the frictional resistance along the pile length of the two kinds of uplift piles. With changing soil layer conditions, the distribution curve may be a "parabola", a "straight line" or a "double line". The soil property plays a decisive role in the frictional resistance, which may cause softening. The influence of the pile diameter on the ultimate uplift bearing capacity is greater than that of the pile length, while the elastic modulus of the pile has little influence.

Finite Element Analysis of Load-Bearing Characteristics and Design Method for New Composite-Anchor Uplift Piles

“…The test results led them to propose the utilization of a coefficient to evaluate the influence of pile installation methods on the pile's bearing capacity. He et al [17] compared the load-carrying capacity of bottom-uplift piles and anchor piles in their study, based on load tests on foundation piles. They found that bottom-uplift piles had double the peak load-carrying capacity of conventional uplift piles.…”

Numerical analysis of pile group, piled raft, and footing using finite element software PLAXIS 2D and GEO5

“…Various foundations are considered depending on the type of construction. Shallow foundations are chosen over deep foundations if the soil carrying capacity is adequate for the weight of the structure 16 , 17 . When the soil carrying capacity is insufficient to support the load of the structure, a deep foundation or a mix of the two is used.…”

Settlement Analysis of Pre-stressed Concrete Pipe-Pile Foundations in Soft Ground: A Case Study

“…Cairo et al used the boundary element method based on the stiffness matrix method to study the key characteristics of soil-structure interaction (SSI) and effectively evaluated the effects of soil-structure interaction with pile foundations under steady-state conditions [1]. HE et al explored the working mechanism and bearing characteristics of bottom-lift piles through the experimental data of pile-bearing capacity tests of a certain project and numerical simulation methods, and they proposed corresponding design suggestions [2]. LIU Jinbo et al concluded that the settlement deformation of prefabricated extruded piles increases with the decrease of pile spacing through the comparative analysis of the influence of pile spacing on settlement deformation [3].…”