Examining Quality of Retaining Wall Made of Mortar and Stones by Means of Comparing Spectrum of Elastic Reflection Wave Frequncy

There are much more retaining wall made of mortar and stones in railway lines, road lines and the other engineering objects. How to examining their quality? The author had test the velocity of elastic reflection wave, Rayleigh surface wave method and Comparing the spectrum of frequency of elastic reflection wave, and had elected comparing the spectrum to examining retaining wall for 5 km in length, because this method have some specialties,such as high resolution, non-interference from materials of mortar and stones, and easiness getting the data.