Predicting the Pullout Resistance of Denti-Steel Strips Embedded in Cohesionless Soil

Abstract

Steel strips as soil reinforcements have two significant advantages over reinforcements with a circular cross section like solid and hollow steel bars. First, the contact area of steel strips is more than that of steel bars when they are compared in terms of their steel volume per unit length. Second, unlike steel bars, most of the contact surfaces of steel strips are perpendicular to the in situ vertical pressure. To further enhance steel strips’ efficiencies, denti-steel strips are presented in this study. This form of steel strips further integrates the aforementioned mechanical advantages by welding several dents along a smooth steel strip. The dents are small rectangular pieces of smooth steel placed at regular intervals. A total of 240 pullout tests consisting of 51 experimental tests and 189 numerical simulations were conducted to evaluate the performance of a denti-steel strip as an innovative bearing reinforcement in frictional soil. Three-dimensional numerical simulations were carried out using the finite-difference package FLAC3D and validated with the experimental results. It was found that the height, number, and relative spacing of dents are dominant factors in the pullout capacity, and, unlike ribbed steel strips with an unchangeable configuration, the optimum dent spacing of denti-steel strips can be designed based on the properties of granular soil. This research introduces a sawtooth failure surface for a denti-steel strip when there is no interference between dents. However, it proposes a block failure surface when there is severe interference between them. These failure surfaces are the bases of developing several rational equations for predicting the maximum pullout capacity of denti-steel strips. The results show that the intensity of interference between dents depends on the spacing-to-height ratio of dents. There are two critical ratios beyond which the interference between dents and failure mechanism significantly change. Numerical simulations indicate that the average normal stress on the reinforcement is more than the applied normal pressure. Furthermore, the average-to-applied ratio of normal stress increases with a decrease in the applied normal pressure.