Study On Calculation Method Of Settlement Of Composite Foundation Reinforced With Geosynthetic Encased Stone Columns

The stone column is widely used in soft soil foundation treatment because of i ts good reinforcement and improvement effects of anti –seismic liquefaction,drainage consolidation and compaction.However,the crushed stone is a loose material without cementation strength,which can only be formed into a pile under the constraint of external lateral limiting force.In the treatment of soft soil foundation,the lateral limiting force provided by the soil around the pile is often very limited,which leads to the excessive bulging deformation of the pile body in the bearing deformation proc ess,so that The stone column cannot give full play to its role in improving the bearing capacity of the foundation and reducing settlement deformation.In recent years,a new type of stone column formed by wrapping geotechnical sleeve on the outside of traditional stone column can effectively improve the bearing capacity of foundation and reduce settlement deformation.we call this new foundation treatment method as geosynthetic encased stone columns.At present,the exploration of composite foundations reinforced with geosynthetic encased stone columns is still in the primary stage,and the bearing deformation mechanism has not been fully revealed.Therefore,this paper studies the settlement calculation method of composite foundation reinforced with geosynthetic encased stone columns.Firstly,geotextiles are simulated using geogrid unit with tensile failure mode added through numerical methods,and the numerical model of the geosynthetic encased stone columns was established.The numerical model has been verified by comparing numerical results with the experiments.The compression tests of geotextile encased stone column under different compaction densities,different geotextile modulus and tensile strength and different confining pressures were simulated.This paper also analyzes the interaction between the pile body and the reinforcement during the deformation process of the geotextile encased stone column,summarizes the bearing mechanism and failure mode,and deduces the formulas for calculating the strength and modulus of geosynthetic encased stone columns based on deformation characteristics during uniaxial compression.Then,a numerical model of composite foundation unit reinforced with geosynthetic encased stone columns is established,and the variat ion law of the pile–soil stress ratio with the buried depth of the composite foundation under different conditions is studied.Considering the strain coordination relationship among pile body,soil and reinforcement,the calculation formula of the pile –soil stress ratio of the composite foundation reinforced with geosynthetic encased stone columns under the rigid foundation is derived using the elastoplastic theory,based on this,the calculation formula of the settlement of composite foundation reinforced with geosynthetic encased stone columns is derived.The analytical solution obtained by using the settlement calculation formula of this paper is compared with the literature results,which verifies the correctness of the calculation formula of this paper,and through parameter analysis,the effects of the stiffness of the reinforcement,the load level,the ratio of the pile–soil modulus,and the area replacement rate on the pile –soil stress ratio and settlement deformation characteristics of the composite foundation are discussed.Finally,the load–bearing deformation curve obtained by using the method in this paper is compared with the results of field static load experiment in an engineering example,which verifies the rationality of the settlement calcul ation method for the composite foundation reinforced with geosynthetic encased stone columns in this paper,so as to provide some reference for the engineering practice.