Research On The Pile-Soil Interface Characteristics And Negative Friction Under Water Level Fluctuation

The pile which built in the lake area is under the water level fluctuation typically.The water level fluctuation is one of the most important element which caused the softening and compaction of soil, the deterioration about friction coefficient which of interface between pile and soil, and the negative friction. In order to get the working mechanism of pile which built in the lake area under the water level fluctuation, the pile engineering of the high embankment in Yue-Chang Expressway that located in the Dongting Lake area which was chosen to be the research object, employing on-site survey, indoor and outdoor experiments, theoretical analysis and numerical calculation, this paper launches a research on the pile-soil interface characteristics and negative friction under water level fluctuation. The main research works and achievements are as follows:(1) Combined with the water level of Dongting Lake and the study of variation characteristics about the groundwater level of surrounding area, the seepage in the soil, the mechanism about softening and compaction of soil which due to the environment of water level fluctuation had been analysis.(2) The change law about moisture content of soil under water level fluctuation was gained by analyzing the drill core test data from the field. The evolution law of friction coefficient which of interface between pile and soil with changing of water level was obtained through a large amount of tests, And the calculation model about friction coefficient of the interface between pile and soil had been built, which based on the strain type friction tester about the interface between pile and soil which is independent development.(3) Based on the mechanism of pile which built in the lake area about the produce and influence of negative friction, the relationship between the side friction and pile-soil relative displacement be supposed to the double broken line form, the calculation model of load transfer which combined with the pile-soil relative displacement and water level fluctuation had been established.(4) Put the pile which built in the Yue-Chang Expressway as the engineering background to form the finite element model by ADINA, then, the influence law about settlement by piledriving and water level variation had been obtained, and the model results had been verified by the settlement monitoring.(5) The pile shaft force of engineering had been calculated by the calculation model of load transfer and friction coefficient which established in this paper, and the variation law about time and negative friction be obtained by the calculation results.