Inelastic Deformation of Sand Reinforced with Different Reinforcing Materials

Abstract

Geomaterial as well as polymer geosynthetic reinforcement are known to have significant visco-plastic property. A series of plane strain compression tests were performed on air-dried Toyoura sand reinforced with four grid types of reinforcement to evaluate the effects of the strength and deformation characteristics (inextensible or extensible; and nearly elastic or highly non-linear elasto-viscoplastic), surface conditions (smooth or rough) and the degree of in-plane dispersion of reinforcement. The effect of reinforcement stiffness on the pre-peak stiffness and peak strength of reinforced sand was not significant, while the effects of the surfaced roughness and the degree of in-plane dispersion were more significant. Significant viscous effects on the vertical stress - vertical strain behaviour of reinforced sand were observed, which were due mainly to the viscous property of sand. The tensile load in the geogrid reinforcement arranged in the sand subjected to sustained constant vertical load decreased with time, indicating that the current design method to evaluate the long-term tensile strength of geosynthetic assuming that the constant tensile load is maintained for life time is on the safe side, perhaps overly. The residual strain of reinforced sand can be made very small by preloading and further sustained loading at the preloaded state, making the effects of reinforcement stiffness negligible.