Hyperbolic models for a 2-D backfill and reinforcement pullout

Abstract

ABSTRACT: A series of direct shear tests were performed using an idealised two-dimensional test medium consisting of rhombically stacked steel rods to facilitate displacement computations for reinforced slopes using a force-equilibrium-based finite-displacement method. A series of pullout tests using extensible and stiff reinforcement with various embedment lengths (Lt) were also performed. Modelling for the non-linear behaviour of shear stress–displacement and pullout force–displacement relationships was performed using hyperbolic models. In modelling shear stress–displacement relationships for the steel rod backfill, a linear Mohr–Coulomb failure envelope was assumed for the investigated range of confining pressures. It was found that model parameters for the initial shear stiffness, namely K and n, are significantly different from those for ordinary soils because of the regular and dense packing of the steel rods, but are advantageous as a backfill material for model tests because of its consistency and repeatability. Results of hyperbolic curve fitting for the pullout force–displacement relationship indicate that the model parameters describing non-linear and pressure-dependent behaviour of reinforcement pullout, namely Kt, m, and Rt, are functions of Lt. The modelled hyperbolic shear stress–displacement relationships and the pullout force–displacement relationships are in good agreement with the experimental ones and are applicable for simulating the behaviour of model slopes consisting of steel rod assemblies.