## 1 Introduction  
The soil nailing system is a technique for stabilizing earth slopes and it is constructed in successive phases, as first illustrated by [PERSON] et al. [1], from top to bottom as excavation proceeds. A soil-nailed slope consists of three main elements, namely, the soil, steel reinforcements bars (nails), and the facing. The elements' composite interactions determine the deformations and stability behavior of a soil nailing system. The shear and tensile strengths of the reinforcing element will increase the overall shear strength and self-supportability of the in situ soil. The function of the facing in a soil nailing system is to ensure the local stability of the ground between the nails and to limit its decompression; the facing should be flexible enough to withstand ground displacement during excavation [2]. [PERSON] et al. [3] have thoroughly reviewed the advancements in the soil nailing technique, different installation processes, failure modes of soil-nailed structures, design philosophies, effects of various construction parameters on the design method, and the analytical, numerical, field and lab testing procedures in the nails' pull-out capacity. [PERSON] et al. [4] submitted state-of-the-art practice documents (NCHRP Project 24-21) related to the analysis, LRF design, and construction of soil-nailed walls for highway applications. The accuracy of the pull-out capacity of the nails will result in the economical and safe design of the soil-nailed structure [5]. [PERSON] [6] analyzed and designed soil nailed walls in expansive soils and the recommended guidelines to improve the design procedures for soil-nailed walls, considering the lateral pressures generated by soil expansion. A simplified method to determine the movement at the crest of a soil nailed wall is developed by [PERSON] et al. [7] who concluded that soil effective cohesion has the greatest effect on crest displacement of the wall. Centrifuge and numerical tests were conducted by [PERSON] and [PERSON] [8] to study the significance of slope facing on the stability and deformation behavior of soil-nailed slopes subjected to seepage. They found that soil-nailed slopes without facing experience face failure due to bearing failure at the slope surface and the nail head surface as well as due to the build-up of excess pore water pressure at the toe region. The influence of the bending stiffness of the facing material--installed on a nailed slope surface of dense sand--on deformation and bearing capacity characteristics were studied by [PERSON] and [PERSON] [9] by conducting tests on rigid and flexible models of footings. Several nailed soil-retaining structures were instrumented to establish a database for the evaluation of structure performance and development of reliable design methods. The material point method-based numerical model was developed by [PERSON] et al. [10] to study the application of plate anchors for landslide stabilization. The numerical model was validated with the results of some small-scale laboratory tests. [PERSON] et al. [11] carried out the shaking table tests to study the seismic behavior of nailed soil slopes. They found that the model nailed slope with a nail inclination of 15\({}^{\circ}\) provided a better reinforcement action than the horizontal and 30\({}^{\circ}\) inclined nails when stabilizing soil slopes. The failure modes of the slope stabilized by a frame beam with prestressed anchors were studied by [PERSON] et al. [12] on a large-scale shaking table. They observed that the seismic damage of the slope stabilized by the frame beam with prestressed anchors mainly occurs at the top of the sliding mass and on the free surface of the slope. A simplified limit equilibrium method is presented by [PERSON] et al. [13] to analyze the stability of slopes reinforced with anchor cables, considering the nonlinear Mohr-Coulomb strength criterion for shear failure of the slip surface. The seismic design of the soil nailing was carried out by [PERSON] et al.