The Research Of Vibration Isolation Performance Of The Wave Impedance Block Under Moving Loads

Nowadays,the environmental pollution caused by the various artificial vibrations is becoming more and more obvious,and the international listed the vibration as one of the seven environmenta l hazards in the world.Based on this context,it 's particularly important and has a quite high application value to study on the vibration isolation measures in the vibration problems.According to the environmental vibration which is caused by the moving loads,a series of study work was carried out in this paper.As a kind of barrier isolation measure,the wave impedance block(abbreviated to WIB)has given rise to a large number of scholar 's research and has achieved a series of remarkable achievements since proposed.However,there were few systematic studies by combination of theoretical analysis,measured and simulation in previous studies,so the results obtained had limitation to some extent.In this work,taking the actual vibration isolation effect of wave impedance block under moving loads such as highway traffic as the research object,the vibration isolation effects of wave impedance blocks made of three different materials are studied through the methods of theoretical derivation,field test an d the finite element simulation.It will provide certain valuable reference for the application of the new isolation barrier in solving the problems of environmental vibration induced by traffic loads in practical engineering.The main research contents ar e as follows:1.Vibration isolation of the wave impedance block under moving loads through the field testBy taking the field measurement near the highway,the actual vibration isolation effects of wave impedance blocks in the ground under highway traffic loads are studied.Considering two kinds of loads such as truck and road roller,we tests the surface vibration response of foundation near highway in four conditions where have no wave impedance block and three kinds of wave impedance blocks made of plai n concrete,geofoam sandwich and sand-free concrete different materials in the foundation respectively.T he results show that under the highway traffic loads,the vibration response can be effectively reduced by setting the wave impedance block;the vibrat ion isolation effect of the wave impedance block made of geofoam sandwich is the best,and the wave impedance block made of sand-free concrete is the second.2.The time-domain finite element simulation of the non-splitting perfectl y matched layer absorbing boundary condition under moving loadsBoundary reflection is a key problem in the numerical simulation of wave field.Because of the semi-infinite space structure of foundation,we must make the influence of the boundary reflection generated by artificia l truncation on the real wave field decreased or eliminated before the actual finite element simulation,so in this paper,we choose the perfectly matched layer(abbreviated to PML)absorbing boundary condition which has been proved to have a better absorb ing performance to minimize the reflection of artificial boundary and improve the accuracy of the results in simulation calculation.Firstly,based on the linear elastic dynamics theory and combined with the transformation of moving coordinate,the second-order elastic wave equation of homogeneous isotropic elastic medium in the moving coordinate system is derived;T hen,according to the transformation of Fourier and complex stretching coordinate,a kind of non-splitting perfectly matched layer(abbreviated to NPML)absorbing boundary is established by introducing auxiliary functions;After that,using Galerkin approximation method for the above NPML absorbing boundary condition,it obtains the time-domain finite element calculation model with the form of displacement;Finally,the effective absorbing performance of the non-splitting PML under moving loads is verified to use numerical examples in the elastic wave problem.3.Establishment of the finite element model of vibration isolation system with wave impedance block under moving loadsThe field test is numerically simulated by finite element method.At first,ther e are brief descriptions to some important problems in the analysis of the foundation vibration when using the finite element method,and accord ing to it,the simulation is developed;Next,based on the second-order elastic wave equation in the moving coordinate system and adding the PML absorbing boundary condition to around of the truncated calculated area,the finite element model of vibration isolation system of the wave impedance block under moving loads is established,and the vibration isolation performance of wave impedance blocks with three different materials that placed in the elastic foundation is calculated;At the last,putting the simulation results under the same condition of load compared with the results obtained from field test,it not only proves that the wave impedance block has a better vibration isolation performance for the foundation vibration problems caused by moving loads,but also provides a strong technical support for the parameter analysis of the wave impedance blocks made of geofoam sandwich and sand-free concrete under moving loads in the future,which can effectively improve the application level of wave impedance b lock in partical engineering.