Optimization of Nails Inclination in Slopes Stabilized by the Soil Nailing Method

Soil nailing is one of the common methods used to stabilize excavation walls. This technique has been in attention in recent years. A variety of studies have been performed to optimize the pattern, length and inclination of nails in the design of soil nailing. The nail inclination has been one of significant optimization variables considered in previous studies. As a constraint of the optimization process, it has been assumed in previous studies that the inclinations of all nails through the depth of a soil-nailed wall must be equal. On the contrary, the present study presumes that the inclination of each row of nails could be different; in other words, the inclination of each row of nails is an independent optimization variable. The present study takes into account two approaches to optimize the design of soil nailing. In the first approach, the ratio of the maximum length of nails to the wall height is unconstrained but in the second approach, it is limited to the ratio proposed by the FHWA manual. The results of the present study show that two optimization approaches lead to different optimized inclinations for nails. For the first approach, the optimized inclination of all rows of nails equal to be 5 degree with respect to the horizon but in the second approach, these inclinations are different for rows of nails in the way that they reduce from the top row to the bottom one.