Feasibility of the P- and S-beam methods for stability estimation of the Daegok dam in Korea
We investigate the feasibility of using the P- and Sbeam seismic methods to evaluate the stability of dams, employing these methods to analyze the Daegok dam in Korea (a concrete faced rockfill dam; CFRD). In the beam method, adjacent shot gathers are stacked to generate super shot gathers, which can be similar to those obtained using a group of shots or groups of geophones. In the super shot gathers, surface waves and unwanted noises may be suppressed due to phase shifts that occur at adjacent shot gathers, whereas deep reflection events with slight phase differences may be enhanced. For this reason, deep reflection events can be better imaged than shallow ones. By applying the P- and Sbeam methods to the Daegok dam, we were able to image the interior structures of the dam and determine physical properties such as velocities and the Poisson’s ratio. Compared with the velocities obtained from borehole P-S logging for other rockfill dams, the velocities and Poisson’s ratio obtained for the Daegok dam are reasonable. Given that a strong source generator cannot be used with dams because it might damage them, we feel that the P- and S-beam methods can be effective means of evaluating dam safety.