## 1 Introduction
[14] with varying geometrical and mechanical parameters for the nail and soil of a slope. They observed that the global factor of safety increased with soil cohesion and friction as well as the nail length, diameter and inclination; nail inclinations higher than 15\({}^{\circ}\) reduced the factor of safety. [PERSON] et al. [15] proposed a new approach for the stability analysis of soil-nailed walls and concluded that the shear strength of soil has a significant effect on the factor of safety and the reliability index of soil-nailed walls. [PERSON] et al. [16] presented the performance of very deep, temporary soil-nailed walls constructed in a very seismically active region. The displacement data for various projects were evaluated in terms of various design parameters of the soil-nailed walls and the excavation depth. [PERSON] and [PERSON] [17] studied the performance of a soil-nailed wall supporting a vertical slope under both static and seismic conditions by observing and computing the maximum lateral displacements, development of nail forces and failure modes of soil-nailed walls. Numerical analyses of the stabilizing mechanisms of loose fill slopes were carried out by [PERSON] et al. [18] to study the influence of hybrid nail orientations on the behavior of the ground nailing system and concluded that the hybrid nail arrangement would limit slope movement and enhance the robustness of the system. [PERSON] [19] applied Bishop's Simplified Method to evaluate and rank the sensitivity of the soil properties, namely cohesion, unit weight and internal friction angle, with respect to the global factor of safety, using the Monte Carlo simulation in a soil nailing design. He showed that the internal friction angle is the most sensitive parameter, while cohesion and unit weight are less sensitive with respect to the global safety factor. [PERSON] et al. [20] developed non-destructive test methods for evaluation and checking the integrity of installed soil nails. [PERSON] et al. [21] present the re-assessment stability analysis of soil nailing design and construction in heavily weathered granite (residual soil), using a limit equilibrium sliding block method (bi-linear failure surface). They found that even after a maximum acceleration of 0.63 g of a stronger earthquake, the nailed wall did not show any damage, probably due to the use of undrained shear strength parameters. [PERSON] [22] studied the hybrid, mechanically stabilized earth and soil nail wall system and proposed the optimum length of nails required to stabilize the structure and reduce the wall deformation. A slope stability analysis of a combined system of soil nails and stabilization piles on loess soil is presented by [PERSON] et al. [23]. [PERSON] et al. [24] proposed the optimization of soil nailing parameters for soil-nailed structure design, using the genetic algorithm method. A composite silt-soil nailed symmetrical foundation pit was numerically investigated by [PERSON] et al. [25] for stability and deformation characteristics. They found the critical values of inclination and spacing of the soil nails, and the diameter and embedded depth of the mixing pile for stability of the foundation pit. Despite the numerous research studies on soil nailing system behavior, laboratory modeling studies of various soil nailing system parameters are not sufficient and further parametric study under varying surcharge loading is clearly needed. The present paper studies the performance of soil-nailed slope physical models with varying nail parameters and surcharge loading. Three important nail parameters, namely, the length of the nail, the nails spacing and the angle, were selected for the study; the effect of the length, spacing and orientation of nails on the force mobilized in the nail, lateral displacement of the slope, settlement of the footing and the earth pressure at the slope face, under and behind the soil mass at various surcharging loading were observed.