Automated inversion procedure for spectral analysis of surface waves

The usual inversion procedures for spectral analysis of surface waves (SASW) testing assume that only one Rayleigh mode is dominant, and thus fail to give reliable results for irregular soil profiles and some complex pavement systems. A new inversion algorithm is presented that is based on the numerical simulation of an actual SASW test, thus enabling the contributions of all types of waves and their modes to be taken into account. The algorithm also benefits from a nonlinear minimization technique in addition to the current linearized minimization to improve robustness of the inversion. Artificial irregular profiles, including a profile with a softer layer trapped between two stiffer layers, a profile with a stiffer layer sandwiched between two softer layers, and a profile with softer layers at larger depths, as well as two experimental pavement profiles have all been successfully inverted.