Formation and Propagation of Love Waves from a P-Wave Source

摘要

The objective of this research is to investigate experimentally, and support byfinite element calculations, the formation and propagation of Love waves from a P-wave source due to scattering at material heterogeneities. A series of experiments were conducted where surface strains were measured parallel and perpendicular to a planar granite scattering surface. The granite wall cast in a surface layer waveguide of a low-impedance grout and then cast on a granite base provided the interface for generating horizontally polarized (SH) waves in the surface layer. The in-plane shear waves are the Love waves we measured at the surface. The P-wave source was a 1-cm-diameter spherical explosive of PETN diluted with microballoons to provide a charge density of 0.45 g/cm cast in a styrofoam sphere to further attenuate the peak pressure. We successfully measured the strains at three locations parallel to the wall and two locations perpendicular to the wall, and the test repeatability was good. Good agreement was also observed between the measured and calculated strain at all locations. The code calculations also showed that in-plane shear strains form along the surface layer/granite interface, and these shear strains propagate with little reduction in amplitude but transform relatively high-frequency oscillations to low-frequency wave packets. The experimental configuration used to generate and measure Love waves, an evaluation of the source used in the surface layer experiments, and results from finite element code calculations of the experiment are presented.