Test Study On Behaviors Of Cast-in-situ Concrete Thin-wall Pipe Pile Under Lateral Load

The cast-in-situ concrete thin-wall pipe pile (simple named PCC) is a new pile technology developed by the Research Institute of Geotechnical Engineering of Hohai University, used to the soft ground treatment. Compared with other kinds of pile, the PCC pile has some preferable merits, such as, short construction time, low construction cost and easy operation etc. Currently, this new technology has been used successfully in Jiangsu, Shanghai and Zhejiang etc. But as a new pile technology, the theory study is dropped behind its application, and most attentions now have been given to the vertical load carrying properties, the study on its lateral load carrying properties is few, so it is necessary to carry out some studies on the lateral load carrying properties. In addition, theories we have now on pile lateral load carrying property are deficient, they are also needed to be perfected.Because of these problems given above, some test studies and theoretic analysis were carried out to research the lateral load carrying properties of PCC pile and some helpful conclusions were drawn, and an elastoplastic analysis model and its solution were given. The main contents of the current research are as follows:1) Status of the research of pile lateral load carrying properties was reviewed, and some main existing theoretic methods were also compared and analyzed, at last, some questions that needed to be solved were discussed.2) In order to primary analyze the lateral behaviors of PCC single pile, some model test were carried out, through these test, the hyperbolic relationship between the lateral displacement of pile at the ground surface and the lateral load is analyzed using the least squares techniques, and the power function relationship between the maximum moment of pile and the lateral load is also presented. Meanwhile, some factors, such as pile diameter, pile length, and the layered soil, that influence the pile deformation propertywere also analyzed, and some valuable conclusions were presented.3) Based on Hangqian highway engineering, some field tests of PCC single pile were carried out, and through these tests, the pile deformation characters, lateral bearing capacity and the effect of different load pattern were analyzed.4) According to the elastoplasticity of soil and non-linearity of pile soil interaction, an elastoplastic method for lateral loaded pile and its numerical solution based on Gleser finite difference were presented, and the elastic-plastic results were compared with test results and traditional elastic results calculated by m method, results show that the elastoplastic method is reasonable.5) Using the elastoplastic method, factors that effect pile lateral behaviors, such as pile structure, soil character were analyzed generally, and some useful conclusions for practice were concluded.6) Through model tests and theoretic calculations, the lateral behaviors of PCC pile and other circle solid and square solid pile that with same cross area were compared, results show that the capability of PCC pile resisting lateral deformation is better than the solid piles.