Investigating composite behavior of Geosynthetic-Reinforced Soil (GRS) mass

A study was undertaken to investigate the composite behavior of a Geosynthetic Reinforced Soil (GRS) mass. Many studies have been conducted on the behavior of GRS structures; however, the interactive behavior between the soil and geosynthetic reinforcement in a GRS mass has not been fully elucidated. Current design methods consider the reinforcement in a GRS structure as "tiebacks" and adopt a design concept the reinforcement strength, Tf, and reinforcement spacing, Sv, have the same effects on the performance of a GRS structure. This has encouraged the designers to use stronger reinforcement at larger spacing, as the use of larger spacing will generally reduce time and effort in construction.;A series of large-size Generic Soil-Geosynthetic Composite (GSGC) tests were designed and conducted in the course of this study to examine the behavior of GRS mass under well-controlled conditions. The tests clearly demonstrated that reinforcement spacing has a much stronger effect on the performance of GRS mass than reinforcement strength. An analytical model was established to describe the relative contribution of reinforcement strength and reinforcement spacing. Based on the analytical model, equations for calculating the apparent cohesion of a GRS composite, the ultimate load carrying capacity of a reinforced soil mass, and the required tensile strength of reinforcement for a prescribed value of spacing can be determined. The model was verified by using measured data from the GSGC tests, measured data from large-size experiments by other researchers, and results of the finite element method of analysis. Since GRS walls with modular block facing are inherently "flexible", an analytical procedure was also developed to predict the lateral movement of the wall system. The procedure also allows the required tensile strength of the reinforcement to be determined by simple hand-calculations. In addition, compaction-induced stresses which have usually not been accounted for in design and analysis of GRS structures were investigated. An analytical model for calculating compaction-induced stresses in a GRS mass was proposed. Preliminary verification of the model was made by using results from the GSGC tests and finite element analysis. The dilative behavior of a GRS composite was also examined. The presence of geosynthetic reinforcement has a tendency to suppress dilation of the surrounding soil, and reduce the angle of dilation of the soil mass. The dilative behavior offers a new explanation of the reinforcing mechanism, and the angle of dilation may be used to reflect the degree of reinforcing of a GRS mass.