Study On Negative Skin Friction For Pile Foundation Of Building

With the development of technology, pile foundation has been the important foundation more and more prevalent as it's the best carrying capacity. Especially, with increasing of ports, coast or hydraulic engineering and the advancement of constructional technique, pile foundation has been used in more and more important engineering. However, because of ignoring the effection of negative skin friction, there also were more and more accidents in actual engineering; for example incline or collapse phenomenon has happened on many buildings as the foundations' unequality settlement. Actually, the negative skin friction phenomenon which has become generalization, severity and specialization has been regarded by many designers and scholars. So this paper has carried the systemic research aiming at single pile and piles group foundations' negative skin friction with model test and FEM methods deeply. Some significative conclusions have been got from the test. The main investigations consist of the following two parts:By the researching of negative skin friction on single pile and piles group foundation under pile head load and soil surface load in two kinds of test, end-bearing piles and end-bearing friction piles, some regulars had been gotten for the load-settlement, axail load of pile, force on pile end and the settlement of differernt soil layers. This paper have emphasized the negative skin friction regulars on the four and nine piles group foundation for the different piles' number, spacing of pile groups, aiming at grow on the comprehension of piles group' negative skin friction mechanism. The result shows that the single pile and piles group foundations' negative skin friction have time effect ; piles group negative skin friction also have piles group effect obviously. The test also shows that negative skin friction is affected by different piles' number, the spacing of piles group and the location of pile.Setting up the pile-soil FEM model by uesing the software ABAQUS, and developing the numerical analysis about the part model test with the parameter of soil which were measured in the lab. The order of two kinds load effection for the negative skin friction was developed in the paper. The results shows that the numerical analysis result almost consistents with the model test. The FEM could be used in the analysis of negative skin friction. The order effection result shows that the negative skin friction under pile head load occurred precede surface load is larger than surface load occurred precede pile head load.