WAVE-PROPAGATION IN LAYERED SOILS - THEORETICAL SOLUTION IN WAVE-NUMBER DOMAIN AND EXPERIMENTAL RESULTS OF HAMMER AND RAILWAY TRAFFIC EXCITATION

A method of calculating the wave field of horizontally layered soils is presented. It combines numerical integration in the wavenumber domain with the matrix method for layered soils in the most simple way. The three-dimensional problem of a harmonic horizontal or vertical point load acting on the surface of the soil is investigated. The method yields the radial, transverse and vertical displacements as functions of frequency and distance, which describe the complete wave field due to a point load of any direction. Results are presented for the vertical displacement due to vertical excitation, as that is the situation which is usually of interest in soil prospecting and vibration analysis. The amplitudes and partly the phases (which yield the dispersion curves of the soil profile) of the complex transfer functions are given for some elementary layered soils, such as a soft layer on a stiffer half-space, a stiff layer on a softer half-space, and continuous variation of stiffness and damping. Comparison of the results with those for homogeneous half-spaces of different wave speeds leads to a general conclusion that usually only the soil material down to half a wavelength of the Rayleigh wave has an influence on the response of the surface, but some significant deviations from that rule are also shown. Experimental results for three different sites due to impulse, harmonic and railway traffic excitation are presented and compared with the theoretical results, and these demonstrate the strong influence of the soil profile on the distribution of wave amplitudes in distance and frequency. © 1994 Academic Press. All rights reserved.