Experimental Study on the Propagation of Low-Velocity Impact Waves in Sand Using Particle Image Velocimetry

Abstract

Particle image velocimetry (PIV) is a hybrid experimental–digital technique that allows for the noncontact measurement of the displacements and strains in granular media. It has seen widespread applications in the laboratory studies of geostatic problems, such as slope failures and ground deformation due to foundation punch-through. In recent years, the development of optical cameras with high temporal and spatial resolution opens the possibility of extending the PIV technique to dynamic problems such as those caused by impact. Using PIV for impact measurements requires the images to be taken at very high frame rates. In this paper, an attempt is made to capture the phenomenon of low-velocity impact wave propagation in sand using PIV. Details of the experimental setup are presented, and the key factors that affect the accuracy of the measurements are discussed. The PIV results are processed to obtain the displacement, velocity, and acceleration histories for particle patches at varying distances from the impact source. Comparisons are made against independent concurrent measurements recorded by two accelerometers embedded in the same soil sample, as well as the results from a dynamic finite-element analysis that computes the displacements and stresses in the sand due to the same impact loading. This study indicates that, for dynamic measurements in low-velocity impact experiments, the PIV technique offers a promising nonintrusive method of capturing the displacement, velocity, and acceleration histories over a wide range of locations in the sand mass without needing to embed sensors in the test sample.