Near-Field Effects on Array-Based Surface Wave Methods with Active Sources

Abstract

Although the capabilities of engineering surface wave methods have improved in recent years due to several advances, a number of issues still require study to further improve the capabilities of modern surface wave methods. Near-field effects, which are one of these issues, have been studied for traditional surface wave methods with two receivers, and several criteria to mitigate the effects have been recommended. However, these criteria are not applicable to surface wave methods with multiple receivers. Moreover, the criteria are not quantitatively based and do not account for different types of soil profiles, which strongly influence near-field effects. A new study of near-field effects on surface wave methods with multiple receivers was conducted via numerical simulations, laboratory simulations, and field tests. Quantitatively based criteria for near-field effects in different soil profiles are presented using two normalized parameters developed in this study. There was excellent agreement between numerical and experimental results, and it was found that underestimation of measured Rayleigh phase velocities was the major symptom of near-field effects.