Journal of Engineering Geology

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Soil nailing is a prevalent method for temporary or permanent stabilization of excavations which, if it is used for permanent purposes, the seismic study of these structures is important. There are a few physical models, with limited information available, for the study of behavior of soil nailed walls under earthquake loading. Numerical methods may be used for the study of effects of various parameters on the performance of soil nailed walls, and this technique has been used in the current paper. In this research, the effects of various parameters such as the spacing, configuration, and lengths of nails, and the height of wall on seismic displacement of soil nailed walls under the various earthquake excitations were studied. To investigate the effects of the configuration and the lengths of nails on the performance of these structures, two configurations of uniform and variable lengths of nails have been used. To study the effects of the spacing between nails and the height of the wall the spacings of 2 and 1.5 meters and the heights of 14, 20, and 26 meters have been considered. The seismic analysis has been carried out using the finite element software Plaxis 2D. To analyze the lengths' of nails, it was assumed that the safety factors of stability of different models are constant, and the limit equilibrium software GeoSlope was used. After specification of the lengths of nails based on constant safety factor of stability, the deformations of the models under several earthquakes records were analyzed, and recommendations were made on minimizing the deformations of soil nailed walls under seismic loading.

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In the narrow geosynthetic-reinforced retaining walls a stable rear wall exists in a short distance and so there is no enough space to extend appropriate length of reinforcements. In this case, the probability of overturning of retaining wall increases especially when subjected to earthquake loading. To increase the stability of the wall, reinforcements may be connected to the stable rear surface. Alternative solution is the utilization of full-height cast in-place concrete facing in order to resist the earth pressure by combined actions of reinforcements pullout capacity and facing flexural rigidity. One of the main questions about this type of walls is the portion of earth pressure resisted by the facing. In this study, the seismic earth pressure of narrow geosynthetic-reinforced backfill on rigid facing was evaluated using limit equilibrium approach and horizontal slices method. The critical failure surface was assumed to extend linearly from the wall toe to the rear surface and then moves along the interface of the backfill and rear surface up to the backfill surface. The effects of various parameters such as wall aspect ratio have been investigated. The obtained results show that the applied soil pressure on wall facing will be increased with depth in the upper part of the wall according to the Mononobe-Okabe equation, but its pattern is inversed in the lower part of the wall and it decreases until it reaches to zero at the wall toe. The results of analyses indicate that the attracted soil thrust by the facing increases with lessening of backfill width.