Pullout resistance of bearing reinforcement embedded in sand

Abstract

Mechanically stabilized earth (MSE) structure has been widely accepted as a retaining structure. Its construction cost is mainly controlled by backfill materials, which are generally coarse-grained soils, and reinforcement type (steel volume). The present paper introduces a new cost-effective reinforcement, designated as "Bearing Reinforcement". It is composed of a longitudinal member and transverse (bearing) members. The longitudinal member is made of a deformed bar, which exhibits a high pullout friction resistance. The transverse members are a set of equal angles, which provide high pullout bearing resistance. The maximum pullout bearing resistance of a single isolated transverse member, sbmax, can be determined by using the plasticity solution based on the modified punching shear failure mechanism. Influential factors governing the mobilization of pullout bearing resistance are spacing, S, leg length, B, and numbers, n of transverse members. The larger the S/B, the lower the transverse member interference. The S/B ratios of <3.75 and >25 are referred to as full and free interference, respectively. The relationship between normalized average pullout bearing stress, σbn/ nσn and pullout displacement, d, where σbn/n is average pullout bearing stress of the bearing reinforcement with n transverse members and σn is applied normal stress, is practically identical for the same level of transverse member interference. This relationship can be modelled by hyperbolic function. From this finding, a suggested procedure for estimating pullout characteristics (maximum pullout resistance and pullout force versus displacement relationship) of the bearing reinforcement for any level of transverse member interference (any S, B, and n) based on a one point test on the bearing reinforcement with a single isolated transverse member is proposed. Good agreement has been obtained between the predicted and the measured pullout characteristics. This suggested method is useful for the internal stability analysis of MSE wall in terms of engineering and economic viewpoints.