VISUALIZATION EXPERIMENT OF SUBBASE MATERIAL EJECTS AND EROSION PROCESS CAUSED BY PUMPING IN PAVEMENT

Abstract

 In this study, model experiments were conducted to simulate pavement pumping, aiming to visualize the process of subbase erosion under repeated wheel loads. In the experiments, an acrylic plate with a slit aperture, simulating a pavement slab with a transverse joint, was placed on saturated silica sand layer, and a rubber tire repeatedly applied a wheel load onto the plate. The soil container, made of clear acrylic, enabled vertical cross-sectional view of pavement plate deflection and movements of sand grains. Fluorescently stained grains were mixed into the sand layer to serve as tracking targets for experimental video processing. The observation revealed that pumping is caused by the combined effects of gradual deflection in the approach slab and rapid deflection in the leave slab under wheel loading; the former pushes the sand grains beneath the approach slab toward the transverse joint, while the latter pumps out the sand grains through the joint aperture. When the slabs are unloaded and deflect upward, turbulent water flow forms beneath the slabs, particularly scouring the subbase surface beneath the joint.