Research On Stress And Deformation Of Uplift-Piles In Loess Ground

With the development of municipal construction, the foundations of the building resisting the uplift load becomes more and more. In this paper, based on the data of static loading test (for three uplift-piles) in loess ground for Xi'an Big Goose pagoda international culture square and Shan xi swimming and diving hall, etc, the utmost bearing capacity, ascending displacement, axial force of the piles and developing mechanism of the side friction are studied.In the first chapter, research results on uplift pile in domestic and overseas are summarized, combined with the loess properties in Xi'an region ,and the major studied content of this paper are put forwarded.In the second chapter, the load transfer rule, the relationship of side friction and ascending displacement, the primary factors influenced the side friction of single uplift pile, the depth effection of side friction, and the bearing mechanism of a single uplift pile are analyzed.In the third chapter, failure modes of uplift piles are introduced, and based on the failure modes, the utmost bearing capacity of single uniform-section pile is studied. At the same time, we predict the utmost bearing capacity with the gray system theory, and compared with the measured value, we can get that the predicted value have better accuracy, and can meet practicing requirement.In the fourth chapter, the testing data of single uniform-section pile is studied, the axial force, the side friction and the end friction of pile when loading are analyzed, through discuss the in-site results, we know the side friction and the bearing capacity characteristics of Xi'an region, finally, the author also give the axial compressive force, the side friction and the end friction of press pile of the same area, according to the static-load tests data, the differences of side frictions between the uplift pile and the press pile are contrastively analyzed. The ratio between uplift piles' side friction and press piles' side friction is closed to 0.82. In the fifth chapter, simulating the test of uplift pile by the finite element method, the result shows that the two curvilinear trend is consistent; at the same time, some factors influenced uplift pileU-δ curve are analyzed, and some suggestions about uplift pile are put forwarded, that can provide instruction for design and construction of uplift pile in Xi'an region .