Field Test And Finite Element Analysis On Negative Skin Friction Of Abutment Pile

Negative skin friction of pile is a familiar problem in engineering. A lot of research result have been carried out on this problem. It has made considerable progress for theoretical research, model experiment and site test on negative skin friction of pile. But most of the researches concentrated on active piles which the negative skin friction is producede by large-area earthfill load around pile. It rarely has research results focused on passive pile or asymmetrically earth fill. For express-way abutment pile, the downdrag load caused by road earth fill is the main bearing vertical load. It's a typical problem of passive pile. Moreover, the embankment fill behind the abutment is asymmetric for the pile foundation. So far, research on this issue is still not enough.In the basis of the predecessors, used field test method and FEM, this dissertati conducted research on negative skin friction of abutment pile. The main work and results are as follows:1) A field test on negative skin friction of an abutment pile is performed at the NingHuai Express Highway. Reinforce meters are set up in the test pile, and its axial force are measured. Thus, the skin friction and the bending moment acquired through calculation. The distribution rules of the axial force, the moment and the lateral frictiongal resistance of pile arc analyzed, and the relations between road height and anyone of them are analyzed, too;The influences of earth fill precompression on them are analyzed.2) The measured neutral point depth factor is about 0.34. The result of the test shown that the estimated neutral point depth by the criterion method is bigger than the real one for an abutment pile. And the ultimate neutral point depth has little to do with the height of the road soil behind the abutment. The causes are also shown in this dissertation, it's shown synergistic effect of the lateral frictiongal resistance near pile tip, More close to the pile tip, the value of the positive skin friction is more great.3) By using the Plaxis software, this dissertation also established a FEM plane strain model whith the abutment pile at the site test as an eprototype. Using Finite Element Method(FEM) to study the abutment pile negative skin friction problem. The FEM numerical computation simulated the construction process, and the impact of earth fill height increasing is considered. The impact of foundation soil consolidation settlement, the impact of earth fill precompression process are taken into account, too. According to the result of FEM numerical computation, the distribution and variation rules of the pile negative skin friction are analyzed. And the suitable time of bridge beam construct is forecasted. Then, the effect of pile head vertical load value on negative skin friction is analyzed.4) An comparative analysis is made between the results of the site test and that of the FEM computation. The difference of neutral point depth between them are also explained by analyse.Finally, the bearing capacity of abutment pile is discussed when it bearing negative skin friction, and some feasible measures are advised for the elimination of abutment pile negative skin friction according to the avove results.