Spectral Analysis of Surface Waves Technique for Measuring the Dynamic Stiffness Profile of Railway Roadbed

초록

The precise evaluation of the railway roadbed stiffness is a very important issue for track maintenance and new line construction. The majority of track deterioration is caused by the weak bearing capacity of railway roadbed. In general, FWD, DCP, PBT, GPR and in-situ boring methods are used for the evaluation of the railway roadbed condition. However there is a need for faster, continuous and accurate techniques due to the train operation in the field. The Spectral Analysis of Surface Waves(SASW) method is one of the techniques that meets these requirements and is based on geophysical technique. This method involves actively exciting surface wave energy at one point and measuring the resulting vertical sur-face motions at various distances away from the source. The layered ground stiffness pro-file is calculated by inversion analysis which is based on a dynamic stiffness or transfer matrix. The advantages of the SASW are : (1) it is a nondestructive and non-intrusive method, (2) more accurate results, (3) a large test area may be covered, (4) above all things, a shear wave is not affected by the moisture content. Recently improved techniques have been reported including, the joint inversion method, passive SASW, CAP SASW, MASW and 2D, 3D tomography. This paper focuses on the application of the SASW method to railroad. And some advanced new techniques and case histories which is applied to various railway locations are presented.