EFFECTS OF OBSTACLES ON RAYLEIGH-WAVE DISPERSION OBTAINED FROM THE SASW TEST

This study investigates the effects of underground obstacles on a Rayl eigh Wave dispersion curve obtained by spectral analysis of surface wa ves (SASW) testing. The SASW test is simulated by a transient response analysis of an axisymmetric finite element method. Both rigid obstacl es and cavities with a variety of shapes and embedment depths are cons idered. Results show strong fluctuations in the dispersion curve obtai ned from the signals recorded by receivers in the vicinity of an obsta cle. The fluctuations are primarily a result of wave reflections from the near and far faces of an obstacle. Results obtained from a finite element model are explained through a comparison with a simple theoret ical model and experimental results are published. Fluctuations shown in the dispersion curve can result in misinterpretation of the shear w ave velocity profile. Wherever obstacles are known to exist, an SASW t est should be performed in a way that minimizes these effects. The par ameters that will reduce or aggravate these effects were studied and a re discussed. (C) 1996 Elsevier Science Limited.