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This research studies geogrid reinforcement of sandy soils under the influence of the three earthquakes (Halabjah, Bolunun, and Ali Al-Gharbi) due to the recent increase in seismic activity and the need to reduce damage to foundations due to settlement. Sand samples prepared with a relative density of 70%, with and without geogrid reinforcement, were tested on a shaking (vibrating table) table. Five geogrid layers were used, respectively. Settlement occurs due to dynamic force, and the plastic foundation was used with dimensions of 100 * 100 * 30 mm. Withstands a static load of 5.294 kN/m2. Increasing the acceleration of the earthquake leads to an increase in the settlement of the foundation in the sandy soil. The greater the number of geogrids reinforcing layers, the leads to a decrease in the base settlement, where the rate of settlement decrease is greater, the lower the earthquake acceleration and the greater the number of geogrid reinforcement layers. The time of onset of settlement and the general pattern of settlement are similar in all cases studied. The rate of settlement is approximately twice as high when the soil is saturated than when the soil is dry, and the effect of geogrids is less for the soil when it is saturated than when it is dry. [ABSTRACT FROM AUTHOR]

Finite element method is used to determine the ultimate bearing capacity of Circular Footing resting on geogrid reinforced sand. The effect of each of the depth ratio of the topmost layer of geogrid (u/D), the vertical distance ratio between consecutive layers (h/D), number of geogrid layers (N), and the effective depth ratio of reinforcement (d/ D) on the bearing capacity were studied, where (D) is the footing diameter. In addition, for all these parameters, depth of embedment ratio of footing (D / D f ) and the angle of internal friction ( φ )on the ultimate bearing capacity were studied as well. In general, the results showed that by increasing the number of reinforcement layers (N), the bearing capacity increased. The optimum value of reinforcement layers was (N=3-5). The optimum depth ratio of the topmost layer geogrid was between (0.25D- 0.3D-0.35D) depending on the angle of internal friction (30°,35°,40°) respectively. The optimum vertical distance ratio between consecutive layers was between (0.325D-0.35D),(0.225D-0.25D) and (0.3D-0.375D). As a result, the optimum effective depth ratio of reinforcement was between (0.95D-1.55D), (0.8D-1.2D) and (0.95D-1.1D) depending on the angle of internal friction (30°,35°,40°) respectively. Also, the depth of embedment ratio of footing was (0D,0.25D,0.5D) respectively. [ABSTRACT FROM AUTHOR]