Micromechanical Analysis of Geosynthetic-Soil Interaction Under Cyclic Loading

Abstract

Granular materials are commonly used in the construction of civil engineering infrastructure. Geosynthetics have been used to improve the performance of these structures in many projects. The interaction between geosynthetics and soil is an important factor that governs the performance of the geosynthetic-reinforced structures. Previous studies on geosynthetic-soil interaction using laboratory and continuum based numerical approach were beneficial for studying the overall behavior of the system, however those investigations did not provide insight into microscale response. To improve the understanding of the geosynthetic reinforcement mechanisms, geosynthetic-soil interaction was studied under a monotonic and a cyclic loading using a micromechanical approach. The micromechanical parameters of the granular materials and reinforcements were calibrated using a biaxial test and a tensile test, respectively. The behavior of granular materials was evaluated under a monotonic and a cyclic loading and analyzed from force and fabric orientation perspectives. Using the calibrated micromechanical parameters, benchmark trapdoor experiments were simulated to establish the simulation techniques for geosynthetic-soil interaction. The micromechanical studies of three practical problems involving geosynthetic-soil interaction were conducted. The practical problems were: geosynthetic-reinforced embankments overlying voids, Geosynthetic-Reinforced Pile-Supported (GRPS) embankments, and geosynthetic-reinforced bases. In the biaxial test simulation of soil, porosity of the soil showed profound influence on the shear strength of soil. Particle gradation had a limited influence on the shear strength under the monotonic loading; however, the particle gradation had a strong influence on the resilient modulus computed under the cyclic loading. In the trapdoor experiments, soil arching was observed as an essentially meta-stable condition. The inclusion of reinforcement in the embankments reduced the settlements measured on the top of the embankments. Geosynthetic reinforcement increased the load transfer to the piles and reduced the load on the compressible soils. The anchorage failure of the reinforcement also controlled the load transfer particularly in the low embankments. In the geosynthetic-reinforced base simulation, the density of base course had a profound effect on a rut depth. The tensile stresses developed in the geosynthetic reinforcement helped distribute the contact forces wider. A relatively small tensile stress developed in the reinforcement; therefore, a very stiff reinforcement was not necessary to improve the performance of the base. An optimum ratio between the aperture sizes to the aggregate diameter was identified for the improved performance of the geogrid-reinforced base.