Abstract
The traditional static load test method has been considered as the most direct and reliable method to determine the bearing capacity of single pile, but it has some disadvantages, such as inconvenient operation, laborious test, high cost, and being time-consuming. In this paper, a new type of pile testing method, self-anchored pile testing method, was proposed, and the in situ test was carried out for the first time. This method allows the upper and lower piles to provide force to each other and does not occupy other construction spaces. It had the advantages of simple operation and being economical and practical. Based on the Q-w curve, axial force distribution curve, and hyperbolic function model of load transfer, this paper studied the evolution law of friction of self-anchored test pile and the load transfer process of self-anchored test pile. The results show that the load transfer process of self-anchored pile-soil interface can be divided into three stages: elastic, elastic-plastic, and limit state. The friction of the upper and lower piles starts from the bottom of each pile and then gradually increases. The soil around the upper and lower piles gradually undergoes nonlinear deformation and shear failure, and the pile soil reaches the yield state. By analyzing the hyperbolic function model of load transfer, it shows that the hyperbolic function model can be better applied to the self-anchored test pile, which has reference value for the selection of the function model of self-anchored test pile in the future.
Highlights
With the development of economy, there are more and more high-rise buildings, and pile foundation has become significant [1]
Self-anchored test pile is a new kind of test pile; place a jack on the top of the upper pile, that is, on the ground, set a vertical through hole in the upper pile, and place a load transfer rod in the vertical through hole when the pile is tested. e steel rebar of the upper pile is anchored on the antiforcing beam, and the jack applies load to the upper and lower piles simultaneously through the load transfer rod. e upper end of the load transfer rod is against the bottom of the jack, and the lower end of the load transfer rod is connected with the cover plate of the lower pile
It is considered that the settlement of test pile is relatively stable, and the level of loading can be carried out. e test photos are shown in Figure 4. e vertical displacement of the upper pile is recorded by the dial indicator at the top of the upper pile, and the vertical displacement of the lower pile is recorded by the dial indicator at the upper part of the load transfer rod
Summary
With the development of economy, there are more and more high-rise buildings, and pile foundation has become significant [1]. E steel rebar of the upper pile is anchored on the antiforcing beam, and the jack applies load to the upper and lower piles simultaneously through the load transfer rod. Place load transfer rod in the vertical through hole. E top of the upper pile is pulled because of the anchorage reaction, while the lower pile is pressed by the jack through the load transfer rod. Nie and Chen [7] used hyperbolic function model and modified parameters a and b in the formula, and the relationship curve between pile top load and displacement was determined. Hyperbolic function model has been applied in uplift pile and top pressure pile, and the coincidence degree is high under different geological conditions. Whether the self-anchored test pile is suitable for hyperbolic function model is still unclear. Through the in situ test, the pile friction resistance-pile-soil displacement curve of the self-anchored test pile is obtained, and the linear fitting is compared with the in situ test results to study the regular characteristics of load transfer of the self-anchored test pile
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