Buckling Analysis And Laboratory Model Experiments For Piles Foundation With High Pile-Column Bridge Piers

With the exploitation of west china and the development of infrastructural construction such as highway traffic in remote mountainous area, it's inevitable to build many viaducts to cross rivers and valleys. And the deformation and stability analysis of pile foundation with high bridge pier are important technical problems on the basis of understanding the structure characteristics of bearing mechanics. Under the supports of the program of the scientific project of Communications Department of Hunan Province "study on the bearing mechanism and optimization design for piles foundation with high bridge piers in mountainous district"(200513), this dissertation researches the bearing and buckling mechanics of pile foundation with high bridge pier from several aspects of theoretical analysis, numerical simulation and model experiment.At first, buckling mechanic of pile-column piles foundation with high bridge piers is discussed in detail. Bridge pier and pile foundation are analyzed as a whole for the firs time and a simplified calculation model of pile foundation with high bridge pier is proposed, in which the influence of pier-pile stiffness and surrounding soil body may be considered. Using energy method the theoretical solutions of critical buckling load and effective length are obtained for different boundary condition of bridge construction stage and working stage.Then the laboratory buckling model experiments of piles foundation with high bridge piers are self-designed. Taking into account of the effect factors of pier-pile length ratio, boundary condition and material stiffness, buckling failure mechanism of piles foundation with high bridge piers are gained. The experimental measured values of buckling load and horizontal displacement at the top of piers are in agreement with the calculated results based on theoretical solutions. Furthermore, buckling effect factors and their influence law are exploited.Finally, improve the finite pole element method by taking the P-â–³effect into consideration. Judge the pile foundation's stability condition by changing ratio of displacements. A Matlab program, which can be applied to calculate the critical load of the pile foundation with high bridge pier, is edited. Then compared the calculated result by this program with that of the laboratory model experiments. The comparison attested the program correction and showed that the error rate of result of the improved finite pole element method is quite less. The accuracy is enough to use the improved finite pole element method in actual projects.Simultaneously, correlative effect factor analyses based on improved finite pole element method show that surrounding soil and pile depth embedded in soil have significant impact on buckling performance, and that structural stiffness enhancement can not obviously improve pier-pile stability because structure buckling failure is not material failure. And soil condition around the piles is benefit for foundation stability in some range under ground. There may be exists an effective depth in piles. The stability analysis of pile-column pile foundation with higher bridge piers and normal pile foundation should take the disadvantageous effect of dead weight into consideration, especially in construction stage.