Trenches or underground walls have been set up in the ground along railways as measures to cut off ground vibrations. However, due to the number of variables involved (such as ground conditions, underground wall scale, construction materials etc), no method has yet been established to quantitatively evaluate the effectiveness of vibration reduction techniques.
      The Railway Technical Research Institute (RTRI) has established a technique to analyze transmission and diffraction of waves through an underground wall in order to quantitatively evaluate the relationship between ground structure and actual ground vibration. This technique provides a method to determine quantitatively the effectiveness of vibration reduction from such parameters as ground structures, underground wall scale (depth, thickness, and construction extension), and construction materials (density, elastic constant, and damping constant). In validation tests on an experimental model and in site tests (around 20 examples), the technique approximately duplicated the effectiveness of vibration reduction actually measured (Fig. 1).
      When compared with numeric simulations such as the finite element method, this technique is far simpler and easier to use, and is effective in planning/designing ground-level vibration reduction measures.