Seismic amplification factor and dynamic response of soil-nailed walls

The satisfactory performance of the soil-nailed walls during strong ground motions and their superior flexibility compared to the other guard structures makes them a preferable stabilizing alternative when the risk of seismic loading prevails. The dynamic performance of a deep excavation during a seismic event is greatly influenced by the characteristics of the input motion (fundamental frequency, amplitude, and duration) as well as the properties of geo-materials. Site effect is yet another factor capable of altering the dynamic response of such structures. It has been proven that such site effects as amplification factor and topography effect can be quite influential in the overall seismic performance of earth structure. The present study investigates the effects of mechanical (nails' axial stiffness and soil-nail interface friction coefficient) and geometrical (angle, length, vertical and horizontal spacing) properties of the nails on the dynamic response and the amplification characteristics of a retained trench wall in both loose and dense soil conditions. It was found that the factors leading to the increase in the stability of the reinforced wall would also lead to the increase in the wall's amplification factor. Moreover, the greatest amplification factor has been computed in the immediate vicinity of the wall, and the factor decreases by moving farther away from the wall, converging to that of the free-field condition. It was also noted that the vertical spacing of the nails is more influential in the control of the settlement of the adjacent ground compared to the horizontal spacing.