A method to estimate the efficiency of ground vibration reduction wall

Among the various countermeasures for rolling stock, tracks and structures that have been discussed to prevent the ground vibration along railway lines, burying a wall in the ground is expected to be a comparatively effective solution to cut off vibration. Since the effect of vibration isolation wall depends on the ground conditions and the materials, size and other conditions of wall-in-ground, however, there are no quantitative designing methods established to isolate vibration. Therefore, we reviewed the results of model experiments and field tests in the past from a new viewpoint and developed a method to quantitatively evaluate the effect of vibration isolation wall. In planning and designing vibration isolation wall, it is desirable to have a simple and convenient method to evaluate its effect. Thus, we composed a moderately simple theoretical model to evaluate the effect of vibration isolation wall in quantitative terms. This model features the following:(1) Assumes that a surface wave (Rayleigh wave) is generated from the railway and that the vibration energy behind the wall-in-ground is the sum of the energy of the transmitted wave through the wall and the energy of the diffracted wave originated from its side and bottom.(2) Applies Kirchhoff's diffraction theory, which is introduced in the fields of optics and acoustics, to the evaluation of the diffracted wave.(3) Applies the one-dimensional wave transmission theory that is normally used and the beam deformation theory by regarding the wall-in-ground as a beam to calculate the transmission rate of the wave transmitted through it.Since it is far simpler than the numerical analysis by the finite element method (FEM), the newly developed evaluation method will be useful for planning and designing vibration isolation wall along railway lines.