INVESTIGATION OF GEOSYNTHETIC-SOIL INTERFACE SHEAR CHARACTERISTICS USING A LARGE DIRECT SHEAR APPARATUS

Abstract

Geosynthetics, including geogrids, geotextiles, and geocomposites, have become increasingly popular as a more sustainable and cost-effective alternative to traditional chemical and mechanical treatments. Geosynthetics could improve pavement performance by providing separation, filtration, and tensile reinforcement, by effectively distributing loads across the pavement structure. This study examines the interface properties of geocomposites used with subgrade and subbase materials. Pullout tests were conducted to assess the interlocking and frictional resistance between the geosynthetics and soils, considering both sides of the geosynthetic in contact with different soil materials. The results indicated that geosynthetic performance varied with soil type, with the weakest interaction occurring in the subgrade-subgrade condition and the strongest in the subbase-subbase condition. The study further quantified the shear stress and friction angle for various soil-geosynthetic combinations, finding that the simulated field conditions fell between the extremes of subbase-subbase and subgrade-subgrade interactions. The measured peak shear stresses exceeded the calculated values by 15% for geocomposites. This discrepancy suggests the need for a correction factor to enhance the accuracy of design predictions, thereby ensuring safer and more reliable geosynthetic applications in pavement construction. The obtained interface shear properties can be applied to develop reliable finite element models. Moreover, the testing methodology can be used to establish reliable numerical models for evaluating the shear behaviour of various geosynthetic materials.