Arching Development in Transparent Soil during Multiple Trapdoor Movement and Surface Footing Loading

Abstract

Soil arching exists in many earth structures, such as pile-supported embankments, tunnels, buried pipes, and retaining walls. These earth structures are sometimes subjected to surface footing loading. Limited studies showed that surface footing loading weakened active soil arching formed in backfill material; however, this effect has not been well considered in the current design. In this study, two-dimensional (2D) trapdoor tests with transparent soil were carried out to investigate the development of active soil arching under static surface footing loading. The particle image velocimetry (PIV) technique was adopted to monitor the deformations of soil particles due to multiple trapdoor movements and surface footing loadings. Soil arches with a triangular expanding pattern and a tower-shaped development pattern were observed in the cases with different fill heights. Under the surface footing load, soil arching first degraded locally (at its crown) and then gradually expanded to both sides of the arch with an increase of load magnitude until full degradation of soil arching globally. The model tests with active soil arching resulted in a larger surface settlement under a footing load than that without soil arching due to the volumetric expansion of the soil during the formation of soil arching. Two analytical methods were compared with the experimental results before local degradation and after global degradation of soil arching.