Analysis of seismic vibrations excited by a moving railway construction

This paper presents a theoretical analysis of seismic vibrations generated by a fast moving train. The possibility of using seismic vibrations of technogenic character, created by the vehicle itself and recorded by the equipment used in seismic exploration of the subsoil, to detect and localize areas of the geomedium under the tracks and in its vicinity, prone to karst phenomena, where the risk of accidents is increased, is investigated. The main physical mechanisms for the excitation of seismic waves traveling along the free surface and going deep into the earth are listed. Particular attention is paid to Rayleigh surface waves, which dominate at small and medium distances from the path at frequencies up to the first tens of hertz. The calculation of the spectrum of the surface Rayleigh wave, prevailing in the seismic response recorded at the indicated distances, has been performed. The amplitude-frequency characteristics and their dependence on the velocity of movement and on the difference in the velocity of propagation of elastic waves in the sedimentary strata are considered. The graphs of the seismic wave response spectrum at several values of the velocity of movement and parameters of the upper layer of the sedimentary strata are shown as a relief on the plane of arguments: frequency - distance along the perpendicular. The effect of the frequency dispersion of the velocity of propagation of surface waves in a layered structure under the mainline on the spectrum of the wave response is analyzed. The characteristic features in the relief, depicting the spectrum in two-coordinate representation, are considered as informative features that are laid down in the algorithms for monitoring the layered structure of the soil, as well as the basis for the operation of diagnostic systems for local anomalies caused by karst phenomena under the highway.