The Study On Rail Transit Vibration Isolation Of In-filled Trenches Based On Periodic Structure Theory

Periodic infilled trenches have been applied in the civil engineering as an effective vibration isolation measure.However,there are some limitations,such as:(1)Flexible infilled materials are unstable in the process of installation and work.But few researchers have investigated to overcome the instability of the infilled material in the soil and ensure the convenience of the installation,while improving the vibration isolation performance of the in-filled trenches.(2)The periodic structure is generally repeated in accordance with laws and it may cause unnecessary waste of material.Therefore,changing the configuration and layout of in-filled trenches can achieve desired vibration isolation effect and save materials.(3)The ground vibration caused by rail transit trains is mainly concentrated in the middle and low frequencies.How to broaden the attenuation domain of low frequency is an urgent issue to be solved.Therefore,the finite element method is used to study the vibration isolation effect of different forms of in-filled trenches for solving these existing issues.Based on periodic structure theory,efficient and low-cost method is discussed to improve the vibration isolation of wave barriers.The main contents are as follows:(1)Thus,the composite in-filled trench composed of EPS geofoam and concrete is proposed in this paper for sake of a good isolation performance of trench and overcoming the drawback of trenches in soil stability problem and in the process of installation.Based on the periodic structure theory,a two-dimensional finite element model is established by COMSOL to calculate the dispersion relation and band gap.And a parametric study is conducted to analyze the influence of main parameters on band gap.(2)The finite element method is used to verify the feasibility of proposed trenches for vibration isolation in frequency domain.A parametric study is performed to investigate the effect of different parameters of periodic composite infilled trenches on vibration isolation in frequency domains.The vibration reduction effect of periodic composite infilled trenches,periodic EPS infilled trenches and periodic concrete infilled trenches are compared under the main frequency range of ground vibration caused by railway.(3)Based on the improvement of the periodic in-filled trenches,the gradient periodic composite infilled trenches are proposed.The response analysis in frequency domain and time domain is conducted to verify the effectiveness of the vibration isolation effect of gradient periodic composite infilled trenches while saving materials.Then,a parametric study is performed to investigate the effect of different parameters of gradient infilled trenches on vibration isolation.Three kinds of gradient infilled trenches with different depth configurations are proposed.(4)An embedded PT-WIB structure consisting of periodic infilled trenches and wave impeding barrier(WIB)is proposed to realize the vibration isolation in low and medium frequency.The vibration isolation performance of three wave barriers(WIB,periodic in-filled trenches and PT-WIB)under different excitation in frequency domain and time domain is studied.A parametric study is performed to investigate the effect of different parameters of PT-WIB on vibration isolation.