Study On The Negative Skin Friction Of Single Piles During The Consolidation Of Ground

The method of geotextile reinforced piled embankments, which is popular in China and abroad nowadays, is a new technique in dealing with weak foundation soils. Compared with the other treatments of the embankment over soft ground, it has the advantages of rapid construction, little lateral deformation and small settlement, and also provides an economical and efficient solution for foundations over soft soils. The research of development of negative skin friction of piles is the basic study in revealing the work principle of geotextile reinforced piled embankments.According to the research background mentioned above, at the beginning, this thesis analyzes the results of soil-structure interfaces test which gives the shear properties of interfaces between soil and structure. The author develops an improved interface model based on conventional hyperbolic model. The new model considered the increasement of shear strength during soil consolidation and loading-reloading situations. One dimensional consolidation theory is used to analyze the increasement of effective stress and deformation in foundation soils. With the use of DQM, the development of negative skin friction of single piles in consolidating soils is solved. The approachment is proved to be reasonable and efficient compared with the results of the finite element method.The influences of using different interface models and different consolidation theories to calculate the negative skin friction of piles are analyzed in this thesis. The study shows that the neutral point has higher values and the maximum axial force has lower values in using conventional hyperbolic model. The present model yields consistent results with that of the interfaces test and finite element method. Different consolidation theories have different results of negative skin friction and settlement of piles. The theory of Terzaghi consolidation gives higher values of settlement which leads to higher values of the settlement of pile head, the resistant force on pile toe andthe axial force of the pile.Study on the effects of variations of pile load and soil properties on the forces and settlements of the pile. The results show that the neutral point will go up and the dragload go down with the increase of the pile load. As though the maximum axial force will increase with the pile load, the value of the increment is less than that of pile load. When the soil has reached certain consolidation degree, the final negative skin friction and settlement of the pile will decrease. The resistant force at pile toe has a big effect on the results of calculation. In order to present the reliable results to the design of pile, the load transfer model and the parameters at the pile toe should be chosen properly.Finally, the present model is used to analyze the negative skin friction of the embankment piles. Assuming a given pile efficiency, the negative skin friction and settlement of the embankment pile are computed. Compared with the finite element method, the results of the approachment in this thesis are reasonable and efficient in analyzing the issues of negative skin friction of piled embankment. Meanwhile, the behaviors of negative skin friction of embankment piles are discussed.