Test Study On Properties Of Negative Skin Friction Of Thin-wall Pipe Pile Using Cast-in-situ Concrete

Thin-wall pipe pile using cast-in-situ concrete(simply named PCC) technique is a new ground improvement technology developed independently by Proc.Liu Han-long te. al. (Geotechnical Institute of Hohai University). It has been checked by scientific department of Jiangsu Province and won the privacy. This new form of pile system is suit for soft areas with short construction time and easy operation. It has a practical value and bright market prospect.As theory develops behind the application does, this status limited the more application and development of this method. The problem of negative skin friction is so hot in pile ground engineering and it is often neglected in PCC study. Based on the former research's work, this thesis researched the question above model test, theoretical analysis and numerical analysis about negative skin friction of PCC pile and its advantages are pointed out. The main contents of the current research are as follows:(1) A new test equipment is developed. With this kind of equipment, the tests of single pile and composite ground have been designed. The load transfer mechanism of PCC pile has been studied through the change of strain and stress of pile and the surrounding soil. The negative skin friction test is also carried.(2) The property of soil plug has influences the PCC pile very much. It is not studied much in previous research. Based on above test, the property of soil plug is studied.(3) The load transfer mechanism of negative skin friction of PCC pile is discussed and the elastic differential equation is established. As studied, the essence of friction is shear deformation of surrounding soil.(4) According to consolidation theory of Terzaghi, The iterative procedure to calculate displacement of pile body is obtained based on finite differential method. The computed results indicate that the method provided in this paper is viable. This method can be referenced by other engineering.(5) The relative displacement of pile-soil is obtained based on the elastic differential equation. The simple method to calculate the negative skin friction of PCC pile is established and results indicate that the negative skin friction doesn't occur inside the PCC pile. This method is more convenient to be used in engineering design...