NUMERICAL STUDY OF THE EFFECTS OF GROUNDWATER AND BED RESISTANCE CONDITIONS ON THE BEHAVIOR OF GEOSYNTHETIC SOIL WALLS

The low soil tensile strength is a major limitation in soil structure, while this limitation can be resolved by reinforcing the soil in a reinforced soil wall system. Geosynthetic reinforced soil walls over the past two decades around the world are considered to be very popular and widely used due to many benefits, such as economic savings, accelerate in construction, apparent beauty and more flexibility, than conventional walls, such as gravity walls. Generally, reinforced soil walls are composed of three parts, the backfill, facing and the reinforcement. The mechanism of the reinforced soil walls is based on the interaction between the reinforcement and the soil, which prevents the soil against ruptures. In most designs of a geosynthetic reinforced soil wall, the bed of the reinforced soil wall is considered rigid. Due to the difference in the behavior of the reinforced soil wall on a compressible or loose bed, relative to rigid bed, investigating the behavior of this system on a compressible bed is considered necessary. In this research, the behavior of geogrid reinforced soil seated on a bed with different resistance parameters and different groundwater levels, using finite element method for the analysis of deformation and forces, and limits equilibrium method for checking wall stability, has been evaluated. Also the effect of wall height, in two categories with a height of 4 and 8 meters is considered and evaluated. The result showed that reducing the resistance parameters bed of reinforced soil wall, would lead to increase lateral displacement of the wall and tensile load of the geogrids, and to reduce the wall's stability, and as the surface of groundwater level closer to the below of reinforced soil wall, the lateral displacement of the wall will be more and the overall stability of the wall will be less, and this effect of groundwater on the wall's behavior is significant at a distance of zero to one meter below the wall. Also, by observing the stability of the walls, when the strength of the bed decreases from rigid to weak, the wall safety factors will be greatly reduced and the slipping surface will close to the wall surface. This is also evident for the existence of groundwater level, which is more perceptible in the bed with poorly sandy soil.