Effect of fine content on the pullout resistance mechanism of bearing reinforcement embedded in cohesive–frictional soils

Abstract

Bearing reinforcement, which is composed of a longitudinal member (steel deformed bar) and transverse (bearing) members (a set of equal angle steel), has been established as an effective earth reinforcement material. The equation for estimating the pullout resistance of this reinforcement in coarse-grained soils has been previously developed. The usage of locally available soils as a backfill is particularly cost effective for construction sites where there is a lack of available quality materials. The pullout resistance mechanism of the bearing reinforcement embedded in cohesive–frictional soils with various fine contents is presented in this paper. The total pullout resistance is the sum of the pullout friction and bearing resistances. The pullout friction resistance is approximated from soil shear strength and interaction factor α, which is linearly related to fine content. The bearing pullout resistance of a single isolated transverse member can be approximated from the modified punching shear mechanism where the failure plane angle, β is primarily dependent upon fine content. The relationship between β and fine content is expressed by a polynomial function. The β value of π/2 is suggested for fine contents less than 45%. The transverse member interference is classified into three zones, depending upon spacing and dimension of transverse member, S/B ratio. The larger softened region caused by transverse member interference develops with smaller fine content. Based on a critical analysis of the test results, the pullout resistance equations for bearing reinforcement with different normal stresses, dimensions and spacing of transverse members embedded in different cohesive–frictional soils compacted at optimum point (optimum water content and maximum dry unit weight) are developed in term of total strength parameters. The application of the proposed equations are finally illustrated and verified. The developed equations is useful for the internal stability analysis of bearing reinforcement earth walls during construction and at the end of construction.