Effect of particle shape on shear behaviour of aggregate-geogrid interface under different aperture ratios

Abstract

ABSTRACT Effects of aggregate size and shape on monotonic shear behaviour of unreinforced and geogrid-reinforced aggregate interfaces were systematically investigated through direct shear tests. Five different grades of angular aggregates and five kinds of rounded aggregates with identical particle size distribution were selected as test materials. Experiment results revealed the coupling effects of particle shape and aperture ratio (AS/D50 ), defined as the ratio of geogrid aperture size (AS) to the average particle size of aggregate (D50 ), on the shear behaviour of the unreinforced and reinforced interfaces. The peak shear stress, shear displacements corresponding to peak shear stress and residual shear stress, as well as maximum dilation of aggregate–geogrid interfaces at each AS/D50 were greater than those of glass beads–geogrid interfaces. The largest interface shear strength coefficient of aggregate–geogrid interfaces was achieved at AS/D50 = 2.55, and the optimum reinforcement of glass beads–geogrid interfaces appeared at AS/D50 = 5.05. The shear strength decreased more after the peak when the value of AS/D50 was relatively small, and the post-peak strength reduction of aggregate–geogrid interfaces was more pronounced. A generalised stress-dilatancy relationship was proposed, which introduced a variable dilatancy index (ζ) that reflected the effects of aperture ratio and particle shape.