Analysis Of Vibration Isolation Performance Of Vibration Isolation Barrier In Unsaturated Soil Foundation

With the rapid development of rail transit,how to reduce the impact of vibration caused by high-speed trains on the surrounding environment h As received extensive attention.Vibration isolation trenches can block the propagation of vibration waves in the propagation path,and are widely used and studied.At present,the commonly used foundation models for studying the vibration response of foundations include singleph Ase foundation model,two-ph Ase saturated foundation model,and three-ph Ase unsaturated foundation model.Every time one more ph Ase is considered,the wave propagation characteristics will be very different.Most subgrade soils are in an unsaturated state,and it is clear that the unsaturated soil foundation model is more in line with the actual situation.In this paper,b Ased on the PDE module of the finite element software Comsol Multiphysics,an unsaturated foundation-vibration isolation trench model is established.The attenuation coefficient of lateral and longitudinal displacement amplitudes and the relative values of lateral and longitudinal average displacements are used As evaluation criteria.Under medium-frequency vibration and high-frequency vibration,the dimensions of vibration isolation trenches(empty trenches,filled trenches)in unsaturated soil foundations(depth,cross-sectional area,cross-sectional form,sidewall inclination,distance from vibration source,number of rows,and spacing of multiple rows of trenches),material parameters(shear modulus)and foundation parameters(saturation,porosity,permeability coefficient,etc.)factors on the vibration isolation effect,compared the vibration isolation effect of single-ph Ase foundation,saturated foundation,and unsaturated foundation hollow trench,The parameter values for the vibration isolation trench to exert the best vibration isolation effect are given.The main research results obtained in this paper are As follows:1.BAsed on the secondary development of the PDE module of the Comsol Multiphysics finite element software,the dynamic equation of the unsaturated porous medium considering the dynamic coordination conditions of the interaction of each ph Ase at the interface is solved.By comparing with the existing analytical and numerical solutions,the correctness and precision of the method and program are verified.2.The unsaturated foundation-vibration isolation trench model w As built,and the influence of the vibration isolation trench size,material parameters and foundation parameters on the vibration isolation effect of the unsaturated foundation hollow trench and vibration isolation trench w As calculated and analyzed,and the single-ph Ase foundation and saturated foundation were compared.,Vibration isolation effect of hollow trenches in unsaturated foundations.The main conclusions are As follows:(1)The influence of the foundation model: the single-ph Ase foundation and the dualph Ase foundation will underestimate the vibration isolation effect of the hollow trench,and the vibration isolation effect of the three-ph Ase foundation hollow trench is the best.For three-ph Ase unsaturated foundation,under the premise of minimum error,it can be simplified to single-ph Ase foundation under medium frequency vibration,and it can be simplified to two-ph Ase foundation under low frequency and high frequency vibration.(2)Influence of unsaturated foundation parameters: The unsaturated foundation parameters have the greatest influence on the vibration isolation effect of hollow trenches is porosity,followed by saturation,and the smallest is permeability coefficient.Empty trenches have better vibration isolation effect in unsaturated foundations with low saturation,low porosity and high permeability coefficient.(3)Influence of the geometric parameters of the hollow trench: changing the inclination angle of the side wall of the hollow trench and the distance from the vibration source h As the greatest impact on the vibration isolation effect of the hollow trench,followed by the depth,number of rows and row spacing of the hollow trench.The vibration effect h As the le Ast impact,and at different vibration frequencies,the parameters for the best vibration isolation effect of the hollow trench are different.(4)Influence of filling ditch filling: when the ratio of the shear modulus of the filling to the soil shear modulus is about 60 or less than or equal to 0.006 times,the vibration isolation effect is the best;the width of the filling ditch is set to the minimum allowable value for construction That’s it.