Spectral analysis of surface wave response of multi-layer thin cement mortar slab structures with finite thickness

The method of spectral analysis of surface waves (SASW), a nondestructive t esting method, has mainly been developed and used for many years in the fie lds of geotechnical engineering and highway engineering, such as for examin ing the material properties of pavement systems and soil media under an inf inite half-space condition. Extensive research in this area has been focuse d on understanding the applicability and limitations of the SASW method in recent decades. This method consists of generation, measurement, and proces sing of dispersive surface waves. During an SASW test, the surface of the m edium under investigation is subject to an impact to generate surface wave energy at various frequencies. Two vertical accelerometer receivers are set up near the impact source to detect the energy transmitted through the tes ting media. By recording signals in digitized form using a data acquisition system and processing them, surface wave velocities can be obtained by con structing a dispersion curve. Through forward modeling, the shear wave velo cities can also be found, which can be related to various material properti es. This paper presents the relationship between the theoretical and experi mental compact dispersion curves when the SASW method is applied to multi-l ayer thin cement mortar slab systems with a finite thickness. The test resu lts of surface wave velocity obtained from the experimental compact dispers ion curve are found to have higher values than the results obtained from th e theoretical dispersion curve due to different boundary conditions and ref lections from the boundaries. An experimental study was conducted to examin e if the dispersive characteristics of a Rayleigh wave exist in the multi-l ayer cement mortar slab systems. This study can be utilized in examining st ructural elements of general concrete structures and can be applied in the integrity analysis of concrete structures with a finite thickness. (C) 2001 Elsevier Science Ltd. All rights reserved.