Study On Transversely Isotropic Model And Mechanical Properties Of Geogrid Reinforced Foundatio

Based on the characteristics of Guizhou province with high mountains and deep valleys and steep slope drop,we designed the indoor plate load test and direct shear test of geogrid reinforced foundation based on a high fill foundation project of a bridge abutment on Guian Avenue,and studied the mechanical properties of geogrid reinforced foundation in vertical and horizontal directions under the action of load,considered the composite foundation as a transverse isotropic medium,and established the relationship between vertical and horizontal deformation modulus and The relationship between vertical and horizontal deformation modulus and reinforcement rate,fill modulus and reinforcement modulus is established,and the calculation methods of additional stresses and displacements in vertical and horizontal directions are further deduced to reveal the mechanism of reinforced composite foundation under the action of load.With the help of VS2010 programming software C++language,the transverse isotropic model of reinforced composite foundation is developed twice,and the numerical tests of plate load and direct shear are carried out by FLAC3D software,and the calculation results are consistent with the results of indoor tests and theoretical calculations,which verifies the rationality of the present model.The model was applied to a reinforced soil high-fill bridge abutment project on Gui’an Avenue to conduct numerical simulation and analyze its mechanical properties,and the main research results were obtained as follows:（1）Based on the basic physical and mechanical parameters of the reinforced soil filler obtained from the conventional indoor physical and mechanical tests,the geogrid reinforced soil composite foundation with no reinforcement,5-layer reinforcement,7-layer reinforcement and 16-layer reinforcement schemes were designed for the plate load test and indoor direct shear test.The results of the flat plate load test show that the geogrid reinforcement can effectively increase the bearing capacity of the foundation at the same location by up to 63.5%,reduce the foundation settlement by up to 45%,reduce the horizontal earth pressure by up to 43%and reduce the horizontal displacement by up to 85%under different working conditions;the results of the indoor direct shear test show that the role played by the friction angle at the interface of the reinforced soil is more obvious in the shear resistance process.（2）Considering the geogrid reinforced soil composite foundation as a transverse isotropic body,the solution methods of transverse isotropic elastic matrix and elastic parameters（E₁、E₃、μ₁、μ₃、G₁）are derived according to the relevant theories of elasticity and composite material mechanics;the relationships between the deformation modulus in vertical and horizontal directions of reinforced composite foundation,reinforcement rate,fill modulus and reinforcement modulus are established;the additional stresses and displacements in vertical and horizontal directions of reinforced soil composite foundation are calculated.The additional stresses and displacements in the vertical and horizontal directions of the composite foundation are compared with the indoor test results and the conventional calculation results,and it is found that the displacement error results can be controlled within 20%,which is more accurate than the conventional calculation results.（3）Based on the secondary development function of FLAC^3D platform,the member functions,base categories,intrinsic registration and information exchange between the intrinsic model and FLAC^3D main program are rewritten by using the built-in model and C++development language in Microsoft Visual Studio 2010 compiler to realize the transversely isotropic model This enables the secondary development of the transversely isotropic model.The generated dynamic link library files were embedded into the FLAC^3D main program,and the numerical simulations were performed for the indoor plate load test and the direct shear test.（4）The transversely isotropic model and the conventional model were applied to the calculation of a reinforced soil high-fill bridge abutment project on Gui’an Avenue,and the stress,strain and damage zone clouds of the bridge abutment were compared and analyzed.The range is smaller than that calculated by the conventional model.When the settlement at the top of the bridge abutment and the horizontal displacement in zone D are compared with the actual monitoring data of the project,it is found that the calculation results of the transversely isotropic model are closer to the actual operation of the project.In this paper,starting from the experimental research on the composite foundation of grating reinforced soil,the transverse isotropic model and the parameter solution method are established,and the secondary development is based on the commercial software platform,and applied to the actual engineering numerical simulation,which improves the numerical simulation technology of geogrid reinforced foundation and can provide some theoretical basis for similar actual engineering design.