Effect of Input Source Energy on SASW Evaluation of Cement Concrete Pavement

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter ($D$) varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance ($S$) and receiver spacing ($X$), and (2) for two different heights ($H$) of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength (${\lambda }_{\max }$) and minimum wavelength (${\lambda }_{\min }$) associated with the combined dispersion curve, corresponding to a particular combination of $D$ and $H$, were noted to increase almost linearly with an increase in the magnitude of the input source energy ($E$). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of $D$. Based on statistical analysis, two regression equations have been proposed to determine ${\lambda }_{\max }$ and ${\lambda }_{\min }$ for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement.