Study On Bearing Deformation Mechanism Of Composite Foundation With Floating Geosynthetic Encased Stone Columns

The treatment technology of geosynthetic encased stone columns composite foundation is based on the traditional stone columns composite foundation,which adopts geosynthetics to surround the stone columns in a circular manner,so as to improve the stiffness and strength of the stone columns,and effectively reduce the settlement of soft soil foundation.The technology makes full use of the characteristics of high tensile strength of geosynthetics,retains many advantages of traditional stone columns composite foundation,and has been applied in the foundation treatment at domestic and overseas,especially in the treatment of extremely weak soil foundation.At present,the research has focused on the conditions of shallow soft soil burial,thin thickness and better bearing capacity of pile ends.However,in China's Guangdong-Hong Kong-Macao Greater Bay Area and coastal areas with deep soft soils,geosynthetic encased stone columns is difficult to penetrate deep soft soil,enter a better bearing layer and is in floating,which has a significant impact on its bearing deformation mechanism.In addition,the composite foundation treatment technology of full-length encased and end-bearing geosynthetic encased stone columns is adopted.When the column length exceeds the effective column length of stone column,the treatment effect cannot be further improved,which not only results in the waste of resources,but also puts forward higher requirements for construction equipment andtechnology.Therefore,based on the existing geosynthetic encased stone columns composite foundation research,in deep soft soil foundation treatment of floating geosynthetic encased stone columns composite foundation treatment technology,through the model tests and numerical analysis method,to deformation of floating geosynthetic encased stone columns composite foundation bearing mechanism carried on the thorough research of the system.First of all,through the unconfined compression test of geosynthetic encased stone columns,the influence of the column diameter on the load-bearing deformation characteristics of geosynthetic encased stone columns is deeply discussed.Eleven groups of model tests with comparability were designed and completed,and the influence of column length on bearing deformation characteristics of single column on composite foundation of floating geosynthetic encased stone columns was studied and discussed.At the same time,the influence of encasement depth on the bearing deformation characteristics of single column on the composite foundation of floating and end-bearing geosynthetic encased stone columns is studied.In addition,the load transfer rule of column under vertical load is studied.Secondly,a three-dimensional finite difference program FLAC3 D was used to establish a numerical analysis model for model test of floating geosynthetic encased stone columns composite foundation.The numerical calibration of the test materials(soft soil,gravel,geogrid)and column mechanical properties based on the research,the effect of column length on the single column bearing deformation characteristics of floating stone columns composite foundation is studied,the critical column length of floating stone columns is proposed,analyses the floating stone columns and floating geosynthetic encased stone columns composite foundation column to bulge deformation,column failure mode and load transfer of column under vertical load are studied.Finally,the use of the established numerical model for parameter analysis,the research discusses the encasement depth,length of column,encasement material stiffness and friction Angle of the column body of floating geosynthetic encased stone columns composite foundation bearing deformation characteristics of the singlecolumn,and puts forward the best encased depth,the best length of column,the best encasement material stiffness and the influence of the change of friction Angle on the bearing capacity of the column body.