Influence of geogrid type and coarse grain size on pull out behaviour of clays reinforced with geogrids embedded in thin granular layers

Abstract

In current article, results of large monotonic pull out tests performed on clays reinforced with two different geogrids (i.e. G1 & G2) encapsulated with thin layers of granular soil of different grain size (i.e. Sand A & B) have been presented. Tests were carried out using a rate of displacement of 1.0 mm/min, normal pressures of 25, 50 and 100 kPa and granular layer thicknesses of 20, 40, 80 and 100 mm. Results showed that encapsulating geogrids in thin granular layers under pull out conditions significantly enhances clay/geogrid interactions and resistance to pull out. Resistance to pull out of geogrid embedded in sand B with larger average grain size (i.e. D50 = 3.1 mm) and greater shear strength were consistently higher than those embedded in sand A with smaller average grain size (i.e. D50 = 1.6 mm) and lesser shear strength. Enhancements also depend on the lower ratio between equivalent thickness of transverse members and the average soil grain size. The rate of resistance mobilisation as well as peak pull out resistance in samples reinforced with the stiffer geogrid (i.e. G1) were consistently was faster and greater than those reinforced with geogrid G2.