Study On Bearing Capacity Of Composite Foundation Of Geosynthetic-encased Stone Columns

With the rapid development of railway construction,many lines need to cross the soft soil sites.Recently,in order to meet the needs of soft soil sites engineering construction,composite foundation of geosynthetic-encased stone columns has been widely used in different fields of foundation reinforcement.The bearing capacity increases significantly,meanwhile,the site deformation control effect is remarkable,which can achieve high social and economic benefits.Up to now,domestic and international scholars did many research on geosynthetic-encased stone columns,and some valuable research results have been obtained.However,there are few researches on working behavior of geosynthetic-encased group stone columns,and the machanism of group columns are not clear enough.On the basis of the research results,the working state of geosynthetic-encased stone columns has been studied and analyzed based on the finite element method.The main contents of the paper include the following:(1)The mechanism of geosynthetic-encased stone columns,and the development of the general situation has been summarized.From the theoretical research and testing methods,combining the construction technology and methods,the previous achievements in the field of research were summed up systematically.(2)Based on the foreign well-known geosynthetic-encased stone columns indoor model test,the nonlinear finite element method is further employed to simulate the model test.The soil in the model adopts the Mohr-Coulomb elastoplastic constitutive model and the reinforced material adopts the elastic element.The contact element is also introduced between the geosynthetic,the soil and the column.The correctness of the model is verified from two angles of the settlement of composite foundation and the strain of reinforced material.On this basis,the model of large size geosynthetic-encased stone columns has been established,and the working characteristics of group columns are simulated and analyzed.(3)Based on single column and group columns model,the influence of parameters such as modulus ratio of stone and soil,stiffness of geosynthetic,length,friction angle of stone,spacing of column and load of column on the working state of single column and group columns has been analyzed.On the basis of this study,the relationship between settlement of single column and group columns are introduced,the influence of modulus ratio of stone and soil,column spacing and upper load on settlement ratio is analyzed,and the expression of settlement ratio under different working conditions is given.(4)The calculation model of embankment-geosynthetic-encased stone columns composite foundation of soft soil site is constructed.The construction process of embankment is also simulated,which is used to analyze the stress-deformation characteristics of composite foundation under two conditions of low groundwater level and high groundwater level.The consolidation settlement of site and the changing process of excess pore water pressure are also solved at the different construction stages.Finally,the influence of stiffened stiffness and pile number on the drainage of site is discussed,which provides the necessary theoretical support and reference for its optimal design.