Study On The Behavior Of Deformation And Load-Transfer Model Of Vertically Loaded Piles

The dominating parameter of piles design under vertical loads is bearing capacity. While in statically indeterminate structures and determinate structures with large settlement, the top settlement of piles also needs to be controlled. In the traditional load-transfer method, which is wildly used in calculating settlement, the soil continuity isn't employed, so the settlement of soil underlying pile base caused by shaft resistance is ignored. Furthermore the large expense and long test time of field test have become the impediments to determine the load-transfer model.Firstly, based on the existing theories, a detailed analysis of the load transfer mechanism of vertically loaded piles has been developed in this paper. Then, in order to break the limitation of load-transfer method without considering the settlement of soil underlying pile base caused by shaft resistance, a revised load-transfer method is introduced through integrating Mindlin's solution of force at a point in the interior of a semi-infinite solid. Secondly, in order to avoid the disadvantage that load-transfer model must depend on large field test, a framework to determine the model parameters from conventional soil tests data bas been established. A compositive method of calculating load-transfer model with present information is proposed by combining preceding framework with Genetic Algorithm and the revised load-transfer method. Thirdly, in order to employ the influence of slime beneath pile base, negative shaft friction and other factors, some methods of calculating settlement of piles in these conditions are introduced by combining with the revised load-transfer method. And an analysis method of controlling bearing capacity by virtue of settlement of pile top is made by combined the compositive method of calculating load-transfer model with the revised load-transfer method after introducing genetic search method. Finally, the program, FLAC3D, which can consider constitutive model of soil and soil-pile interface condition to compute settlement of piles, is applied. The measures of reducing settlement of piles are gotten by using this program to analyze the influencing factors of settlement of piles.