Studying the Wave Propagation in the Soft Soil Medium Subjected to Low-Frequency Dynamic Effects

AbstractDynamic effects on structures are complicated topics, both in theoretical and experimental aspects. This article aims to study more about the characteristics of the waves that originate from a low-frequency source of vibration, propagate through soil medium, and come to attack a receiver building in the vicinity. The virtual experimental method uses a finite element Plaxis 2D model in which the soil medium is compressible, subjected to a low-frequency vibration (i.e., pile driving and an impact loading in horizontal direction, both excitations have the same frequency f = 1.5 Hz). The mechanism of reflecting the waves from the source to the surrounding medium and the ground surface is studied by examining the direction of displacement vectors in different angles of propagation direction. The target focuses on determining the direction of propagation, reflects from the pile tip to the ground surface, and studying the additional settlement of the receiver footing due to the dynamic effects in the far-field. The former is to understand more about the decay of the body waves, and the mechanism of detaching the body waves to surface waves. Some preliminary results on free-domain displacement indicate that the longitudinal P-wave travels from the pile tip to along a line of which the angle is between 72 to 76° to the horizontal direction, and the transversal S-waves are detected at about 18 to 40° to the horizontal direction, and the surface R-wave may travel at a longer distance up to 50 m. The propagation velocity of R-wave in soft soil is calculated by dividing the distance by the time between two arbitrary points in the time-domain displacement, equals 35.5 m/s.KeywordsDynamic effectsFar-fieldLow-frequency responseAdditional settlement