Vol.12 (2022) No. 4 ISSN: 2088-5334 Application of the Nailing Technique to Stabilize a Slope in a Section of the Twinning of Road and Rail Infrastructure Mohamed Ben Ouakkass a,* , Latifa Ouadif a , Ahmed Akhssas a a 3GIE Laboratory, Mohammadia Engineering School, Mohammed V University in Rabat, Morocco Corresponding author: * ben.ouakkass@gmail.com Abstract— Nailing is one of the most widely used stabilization techniques because of its technical and economic advantages. It is a practical and effective solution for the reinforcement of in-place slopes. It consists of placing in the soil high resistance nails to increase the cohesion of the soil and its resistance to traction and shear, which allows having a new material of great capacity. In this paper, we present the slope stability study in a section twinning of the road and railroad infrastructures between the kilometer points (KP) 105+938 and 106+263 of the line connecting Casablanca to Marrakech. The railroad track's topographic constraints and geometric requirements made the nailing method appeal to the realization of the new railroad in this area. The objective of this work is, on the one hand, to present the stability analysis of the slope before the earthwork and the implementation of the new railroad and, on the other hand, to evaluate the performance and stability of the nailed walls. The stability analysis of the soils in this section was verified in terms of safety coefficient using the calculation software TALREN. In the end, it can be concluded that the stability calculation results are conclusive and allow for highlighting the effectiveness of the innovative solution of nailing. This technique can be considered a good alternative to improve the safety and performance of excavation walls. Keywords— Reinforcement; nailing; stability; twinning; slope; retaining. Manuscript received 16 Jul. 2021; revised 18 Nov. 2021; accepted 12 Apr. 2022. Date of publication 31 Aug. 2022. IJASEIT is licensed under a Creative Commons Attribution-Share Alike 4.0 International License. I. INTRODUCTION Soil reinforcement by nailing is one of the practical techniques for improving the mechanical characteristics of in- place soils. This stabilization method is currently undergoing a very significant and widely employed development [1]–[5] due to its many advantages, namely its ease and speed of implementation [6]–[10], but also it preserves the geometry of the treated site. Soil nailing is a versatile and cost-effective technique for stabilizing slopes and retaining structures [11]– [13]. It involves placing metal inclusions or other high- strength materials in the ground. These inclusions increase the cohesion of the soil as well as its tensile and shear strength by producing a new compound material with a high capacity [6], [11], [14], [15]. The nailing technique is a geotechnical solution used mainly to reinforce slopes and vertical excavations. It is a stabilization technology allowing the reinforcement and maintenance of slopes. It began in France with the first nailed soil wall constructed in 1972 [3], [16], [17]. Nailing reinforcement can be used both to construct cuttings retaining walls and reinforce existing slopes. It can also be realized temporarily to support and stabilize the ground during the realization of the works in a building site, or on the contrary, can have a definitive function. In the context of the doubling of the railroad track between Settat and Marrakech, on the railroad line connecting the two major cities of Morocco: Casablanca and Marrakech [18], we proposed to proceed with the nailed wall solution for the stabilization of the embankment in a section of the twinning of the railroad track and the national road N9. This paper presents a case study of embankment reinforcement using the nailed wall method to allow for the placement of the second railroad track. Our objective is to analyze the stability and evaluate the performance of the nailed slope to undertake the widening of the railway rights-of-way and the construction of the new railroad track. The ease of implementation, the economic efficiency, and the performances brought to the nailed soil [19], [20] have made the nailed retaining technique widely solicited universally in temporary and permanent applications. 1498