The Research On Dynamic Response Characteristics And Analytical Methods Of Geotechnical Reinforced Embankment Under Moving Load

Geosynthetics reinforced embankment is a kind of soft soil foundation treatment form formed by base and geosynthetics.It is commonly used in the foundation treatment of expressway and high-speed railway due to the advantages in construction cost and timeliness.Moreover,it can increase the bearing capacity of the embankment and improve the stability of the embankmen t,and it has a good treatment effect on soft soil embankment.However,the theoretical research is still at the primary stage,especially the interaction of the “pavement structure layer-embankment fill-reinforced cushion layer” that needs further study.Therefore,an in-depth and systematic study about the dynamic response characteristic of geotechnical reinforcement embankment under moving load and its analysis method was made by theoretical analysis,combined with the finite element numerical model.Firstly,this dissertation analyzed the mechanism of geo-reinforced body,and summarizes the mechanism of geosynthetics reinforced body.And then discussing the deformation mechanism and load transfer mechanism of the composite interaction for“reinforced body-cushion layer-fill”.Stress and deformation analysis methods of commonly used geo-reinforced bodies are refined to provide ideas for the main research object of geo-reinforced embankments under moving loads.Secondly,based on the theoretical calculation model of Euler-Bernoulli beam and Timoshenko beam on elastic foundation,the deformation analysis method of the single-layer foundation beam considering the friction effect of the beam-soil interface under static load was discussed.Friction resistance di stribution forms were considered to be constant,linear distribution,proportional to the lateral displacement,and the power series solution considering the coupling of vertical and horizontal displacement,etc.On this basis,the pavement structure layer was considered as a viscoelastic foundation beam for the geosynthetics reinforced embankment under moving load.Based on the Kelvin foundation beam model,considering the influence of interface friction effect between pavement structure layer and subgrade soil,the transient problem of finite beam on viscoelastic foundation under traffic load is analyzed.The displacement analytical solution of the viscoelastic foundation beam under half sine wave load is obtained by trigonometric series expansion method,Laplace Fourier integral transformation and inverse transformation.The pavement structure layer on the upper of the embankment,the embankment filling soil layer,and the geocell or multilayer geosynthetic cushion layer was regarded as a composite system,and the geocell or multilayer geosynthetic cushion layer was regarded as a shallow composite foundation beam below the embankment filling soil layer.Considering the bending stiffness of the pavement structural layer,an extended double-layer Euler-Bernoulli beam model is therefore proposed to analyze the deformation under the symmetric vertical load.In this method,the interface friction effects of the beam-soil,the coupling effect of the horizontal displacement and the vertical displacement are conside red,and the influences of the properties of the upper pavement structure and the embankment filling on the geocell or multilayer geosynthetic reinforced embankment system are considered systematically.Thirdly,according to the characteristics of traffic load,based on the double-layer Euler-Bernoulli beam model mentioned above,considering the bending rigidity of reinforced cushion layer and the gravity of embankment filling,the modified double-layer Euler-Bernoulli foundation beam was used to predict th e performance of the geo-reinforced embankment system under traffic loads.First of all,the bending stiffness of the pavement structural layer and the modified bending stiffness of the geosynthetic reinforced gravel cushion were obtained,and then the ana lysis model of the geosynthetic reinforced embankment is established under a moving load.At the same time,the coupling effect of the upper and lower beams on the dynamic response of the upper and lower beams was also considered,and the governing differe ntial equation for the double-layer beam system was derived by using the first-order perturbation theory.The corresponding solution was obtained.Finally,analyzing the characteristics of the traffic load,the moving surface load was chosen for simulation,and the Fortran subroutine was compiled for controlling the amplitude,range,and speed of the moving load.Infinite element was used at the boundary to reduce the boundary effect owing to the model size.Aiming at the viscoelasticity of embankment filli ng,an equivalent linear viscoelasticity model was developed by using ABAQUS user material subroutine to simulate embankment filling.The geogrid was simulated by the 2D truss element,and the geocell was simulated by the 3D membrane structure.Thus,the f inite element 3D numerical analysis model of geosynthetic reinforced embankment was established under a moving load.The spatial distribution characteristics and plane distribution characteristics of the numerical model were analyzed.Based on the finite e lement analysis model,this dissertation discussed the effects of different types of reinforcement,vehicle overload,moving load speed,the height of embankment filling,pavement structural layer stiffness,the ratio of double-layer beam bending stiffness,the ratio of upper and lower soil layer stiffness and other factors on the stress and deformation of the geosynthetic reinforced embankment.The economical design and construction suggestions were given.