investigation and experimental comparison of geogrid and gridanchor pullout resitance for sandy soil

Construction on problematic soils, such as soft soils, is usually associated with numerous difficulties. Soil improvement is one of the available solution to encounter the problem in which the geotechnical conditions and the soilchr material properties are essentially improved. Reinforcement of soil is usually carried with aim increasing soilchrshear strength and reducing the erosion and/or settlement, permeability control and etc... . Geosynthetics are made of the polymer materials which are used as reinforcement in geotechnical projects. Geosynthetics, depending on their application, have different types, which can be referred to as geotextile, geogrid, geonet, geomesh, geomembrane, geocell, geocomposite. Considering the mechanical and hydraulic properties of the geosynthetics, they are used in various fields. The suitable design and use of these materials leads usually to significant increase in the factor of safety, performance improvement, and cost reduction in projects when compared with other classical solution. In recent decades, extensive studies have been conducted on the types of Geosynthetics and their function. On the 3D geosynthetics, however, deep studies are of few. In this study, the soil interaction with gridanchor as 3D geosynthetic (G-A) and the effect of various parameters (transverse distance of anchors from each other, joint angle of anchor to the geogrid relative to the horizon, aperture size and normal steress) for gridanchor has been investigated. Also, their performance has been compared with geogrids as 2D geosynthetics (G). In geogrids, the aperture size of geogrid, tensile strength of the samples and normal steress are considered as variables. The Pull out test is considered as the basic experiment to approach the goals of the current studies. According to the variables considered for each type of reinforcement systems, 50 pullout tests have been performed on the samples. Of these, 13 tests were performed as observational tests to ensure the accuracy of the test results. The soil used in this study is poorly graded sand (SP). Gridanchor is a type of geosynthetics that was first used by Mosallanezhad et al. In 2008. The results outcome of tests indicate that the use of Gridanchor and compared with geogrid has a significant effect on increasing the reinforced substratechr pullout load. The effect of normal stress parameters, anchor installation angle and anchor distance from each other on the performance of the gridanchor has been investigated and optimal values have been proposed. If using geogrid in high normal stress, it is better to use geogrid with higher tensile strength. So that if a grid anchor is used in high stresses, it is better that the distance of the anchors from each other is greater than their distance in low stresses. Generally, the use of three-dimensional geosynthetics performs better at normal stresses and low displacement.