Evaluation of effect of backfill particle size on installation damage reduction factors for geogrids

Abstract

ABSTRACT: The reduction factors used to account for the impact of installation damage on the tensile strength of geogrids employed in mechanically stabilised earth (MSE) walls and reinforced embankments are usually obtained from field tests that simulate actual construction conditions. Although costly and time-consuming, site-specific field tests incorporate the damage mechanisms that may occur in geogrid reinforcements during installation. Several studies have developed empirical relationships for these reduction factors for use in design calculations, typically considering the effects of construction methods and the backfill soil gradation on the damage of geogrids having a given polymer type, manufacturing method, and weight per unit area. One of the issues with these relationships is how to quantify the backfill soil gradation in the empirical relationships. In this study, a series of field test sections were constructed using geogrids with two polymer types and a range of different weights per unit area to identify quantitative relationships that can be used to better estimate the impact of backfill gradation on the reduction factors for installation damage of geogrids. The results from the field test sections indicate that the reduction in tensile strength of geogrids after installation is non-linearly related to the maximum particle size in the backfill soil. Recommended upper-bound relationships for the reduction in tensile strength for different geogrid polymers are presented based on an evaluation of data sets, with a greater reduction factor observed for polyvinyl-chloride-coated woven polyethylene geogrids than for high-density uniaxially-drawn polyethylene geogrids.