Application of Spectral Analysis of Surface Wave Method for Rock Mass Characterization

Abstract

The spectral analysis of surface wave (SASW) was introduced in the 1980s and it has since attracted the attention of researchers because it is a fast, inexpensive, non-destructive, and easy-to-use method for rock mass characterization. The SASW method was applied in excavation classification by Suharsono (2006) as well as in rock quality designation (RQD) determination (Suharsono et al., 2004); determination of flexible pavement and rigid pavement profiles (Ismail et al., 2001); and non-destructive evaluation and characterization of pavement systems (Nazarian and Stokoe, 1984). The aims of this article were to determine the RQD value and to conduct an excavation classification analysis using the SASW method. In the SASW method, Rayleigh waves are generated by impacting the ground with a hammer, which are then detected using two receivers placed on the ground surface and recorded by a spectrum analyzer. Forward and reverse configuration, which generates forward and reverse SASW profiles, is normally obtained by striking the hammer at the two opposite sides of the receivers, as shown in Figure 1. For sampling shallow material, small receiver spacing with high-frequency receivers and high-frequency sources are utilized. For sampling deeper material, low-frequency receivers are used with longer receiver spacing and low-frequency sources. The common receiver midpoint geometry (CRMG) introduced by Cho and Lin (2001), Joh (1996), and Suharsono and Samsudin (2003) was used for the receiver spacing configuration, as shown in Figure 2. Figure 1. Field configuration of SASW method. Figure 2. Common receivers midpoint geometry (CRMG) (after Cho and Lin [2001]; Joh [1996]; and Suharsono and Abdul Rahim Samsudin [2003]). The Rayleigh wave data were collected and transformed to the frequency domain by a dynamic signal analyzer. WinSASW 3.1.3 (Joh, 1996) geophysical software was used for the inversion process to produce profiles of shear wave …