Experimental Investigation On Bearing Performance Of Intelligent Rotated-Expanded Pile

Intelligent rotated-expanded pile which has gained more and more attention in the field of engineering now has received a certain range of applications in engineering practice due to its advantages such as high bearing capacity, small settlement, good seismic performance, short construction period and low cost. But studies on its load-bearing characteristics and load transfer law are still rare. Besides, theoretical research in this field also lags far behind the development of engineering practice. Therefore, the study of intelligent rotated-expanded pile's bearing performance has important value in engineering application. In this paper, the author made a more in-depth analysis of the rotating pile load-transfer law and the construction process both from the field experiment and theoretical study. There are several aspects of the content in this paper, as following:First, the construction technique of intelligent rotated-expanded pile was introduced. Then the basic principles, suitable strata, process and construction of the technical issues were described in details. Intelligent rotated-expanded pile construction adopted fully automated operation on the ground to replace the heavy manual operations. Comparing to the ordinary bored piles and other variable cross-section piles, it was more accurate, efficient and secure. The side effects of man-made factors has been avoided, thus the duration could be effectively reduced and the quality of construction could be improved and the project cost can be economized.Second, the spin field test of pile has been described thoroughly and experimental data have been analyzed. This pile test adopted the self-balancing static loading test method and the dollars and other tests of reinforced components are laid in the pile, the pile load test-settlement curve, lateral friction and the displacement curve and the lateral friction with depth curve were obtained in the on-site testing. Based on the analysis of the test piles, it can be proved that the load transfer characteristics of intelligent rotated-expanded pile were different from cross-section piles and other variable cross-section piles. The load was almost fully borne by the side resistance of piles while start loading; as the load increased, the pile diameter extension segment began to play a role with the side resistance of piles, and the pile side resistance began to decrease load-sharing when the load reached a certain degree, the pile top load was mainly borne by the soil pile, the pile tip resistance ultimately bear the load up to 50%, and the pile diameter segment expanding nearly resistance bears 18%～20% of the total loadThird, based on the load transfer method in Sato Satoru model, a formula to calculate the load-settlement relationship of the expanding pile of the pile's expanding segment was derived. The formula can be widely used in straight piles, belled piles and impacted-expanded piles. By comparing the calculated values and the measured value curve of rotating pile, they well fit each other. Under the same parameters, by comparing the calculated values between rotation pile and straight pile, the result is that rotation pile bearing capacity is far greater than the straight rod pile. According to the theoretical study and field experimental results, the load-settlement laws, the pile axial force distribution characteristics of the pile segment expanding resistance, tip resistance, distribution of friction pile and its change law were analyzed under the influence of external loads.Fourth, This paper presented a calculation method to measure the ultimate bearing capacity of vertical ultimate bearing capacity of single pile of intelligent rotated-expanded pile. The formula was formed on the existing research results and the current test pile data, the effective pile length, pile tip resistance and lateral resistance of comprehensive correction coefficient, the widening of the shape correction factor to play a segment diameter and pile-side area effects and other factors have also been taken into account. Comparing with the measured data, the relative error between the calculated value with the experimental value was very small, hope that the research could provide reference for the design of intelligent rotated-expanded pile.