Study On Deformation And Capacity Of Uplift Piles

Uplift piles are common type of structures for resisting tensional forces, however,the theories about tension piles are far behind of engineering practice. This paper mainlystudied on uplift capacity and deformation of single pile, and gained some beneficialconclusions. The studies of the thesis are consist of the follow contents:1. According to the shear failure surface method, using the failure surfaceequation proposed by Chattopadhyay et al., the ultimate pull-out load calculationmethod was improved on the basis of the force balance relationship between theultimate uplift load and the shear strength along the failure surface and the soil mass,and the analysis and solving process is easier to be accepted.2. Based on the calculus of variations, the deformation governing equation ofsingle pile was derived, and considering the boundary conditions of tension pile, aniterative procedure was used to obtain the parameters of the function, and then thedisplacement and axial force were gained. During the process of analysis, thedisplacement influence function of the lateral soil was concluded, so the solvingdisplacement of pile is no longer dependent on the empirical expressions.3. Useing the displacement influence function gained before, the ideal elastic-plastic load-transfer function of pile shaft was adopted, and when the frictionresistance of pile reaches the limit of friction, plastic slip is occur, but the increase ofthe relative deformation between pile and soil does not affect the de-formation beyondthe contact surface, the analytical solution of load and displacement of uplift pile arederived based on these assumption above.4. The general solutions of stresses and displacement of axisymmetric problem inlayered elastic half-space were deduced by Hankel transform and transfer matrixmethod, and then the stress and displacement solution of single uplift belled pile was deduced by finite difference method. Comparing the theoretical results with model testresults in literature, the correctness of the theoretical derivation formula is verified.5. The vertical-compressive load and uplift load test of bored piles with same dia-meter and length in the same ground were conducted, the difference of the deformationcharacteristics between two type of load directions was analyzed. The displacement ofground surface around the tension piles was observed and discussed during load tests.Lateral load test and uplift combined with lateral load test of single pile were conductedalso, and the difference of the lateral bearing capacity and lateral displacement of pileloaded laterally under the uplift loads and without the uplift loads was discussed. Thesurface deformation and the pile deformation calculated was compared with testing datarespectively, the results shown that the method adopted in this paper was reasonable.