Analysis Of The Mechanism Of Self-anchored Pile Load Test System And Its Application

With progressing of the construction industry, pile foundation has found more and more applications. Therefore, developing an economical and effective pile load test technique becomes a subject of great significance. Compared with normal technique, self-anchored pile load test technique enjoys stronger vitality with its advantages. However, as a new technique, there is a deficiency of thorough research into the mechanism of the pile-soil-bolt system. Integrating with the Communication Science and Technology Project of Hunan Province, the impact of bolt under pile toe imposed on settlement and the error arises in determining vertical bearing capacity of piles because of the discrepancy existing between actual forcing state and simulation during pile load test are analyzed.Firstly, the bearing mechanism of pile and the uplift mechanism of bolt are discussed. On this basis, according to the mechanical characteristics of self-anchored pile load test system, the Mindlin displacement solution has been introduced to establish an analytical solution of the distribution of shearing stress along anchorage section. Then, the vertical displacement caused by pulled anchor is obtained through integration of the vertical displacement at pile top caused by shearing stress along the anchor surface, thus the analytical solution used to analyze the impacts imposed by bolt under pile toe on the displacement at pile top is established. The difference between this vertical displacement and the settlement obtained by self-anchored pile load test is just the settlement at pile top obtained by ordinary pile load test. Therefore, the transformation from load-displacement relationship of self-anchored pile load test to load-displacement relationship of ordinary pile load test is achieved. At last, the influences of changing parameters on vertical displacement are analyzed based on obtained solution.In the second place, given that the pile foundation is also transversely loaded, in order to analyze effects of transverse loading on vertical bearing capacity, under the assumption of'm'method, the power series solution of deflection equation of piles subjected to both transverse loading and axial loading and the elastic analytic solution of stress distribution in the soil surrounding piles subjected to transverse loading are introduced to obtain the variation of the ultimate shaft resistance due to transverse loading. It is regarded as the variation of vertical bearing capacity for transverse loading has little impact on the ultimate base resistance, which lays the basis for correcting the result of pile load test. After that, the established formula is applied to analyze an experiment and the result shows that calculated values conform to tested values. At last, the influencing factors of the variation of limit skin friction of piles subjected to transverse loading are analyzed.Finally, a model test is analyzed by applying the formula established in the thesis, where its reasonableness is proved.