Global Stability of Reinforced Soil with Nail and Tieback Jefferson Lins da Silva 1 , Francisco Shigueo Urakawa 2 , Lucas Deroide do Nascimento 3 , Clever A. Valentin 4 Department of Geotechnical Engineering, Engineering School of São Carlos, University of São Paulo (USP), Avenida Trabalhador Sancarlense, nº 400, São Carlos/SP, Postal Code: 13566-590, Brazil. 1 Professor, D.Sc., Tel.: +55 16 3373 9505, Fax. +55 16 3373 9509, e-mail address: jefferson@sc.usp.br 2,3 Graduate Students, e-mail address: 2 francisco.fsu@gmail.com and 3 lucasdn6@gmail.com 4 M.Sc., e-mail address: 4 cclever@sc.usp.br ABSTRACT The reinforced soil is a good technique and an economical alternative to stabilization of natural or artificial slopes. The appropriated combination of reinforcements can be a solution to reduce costs. This study aims to evaluate the stability of slopes with reinforced soil carried out with nails and tiebacks. The analysis was based on numerical simulations and experimental results obtained in the literature. The computational package used for numerical simulation was Slope/W. The analyses were performed in order to evaluate the effect of the reduction and the rearranging of the nails and also the inclusion of tiebacks. Taking into account the global stability, the safest slope was the one which had the nails more distant to the ground surface. There was not a significant increase in the safety factor of the soil nailing with the increasing of the grout injection. Another important conclusion is that the reinforced soil structure with nails and tiebacks is a good alternative to improve the safety of the slope due to its satisfactory behaviour in the numerical simulations. KEYWORDS: reinforced soil, soil nailing, tieback, global stability, slope, safety factor. I NTRODUCTI ON The reinforced soil is a good technique and an economical alternative to stabilization of natural or artificial slopes. The artificial slopes can be cut off or fill. In literature, there are studies about the use of reinforced soil in field and laboratory, for example, Hausmann and Lee (1978), Clouterre (1991), Chang and Milligan (1996), Franzen (1998), Morris (1999), Hong et al. (2003), Lee et al. (2204), Junaideen et al. (2004), Chu and Yin (2005), França and Bueno (2008) e Silva and Bueno (2010). These works deal with the soil reinforcement by inclusions of steel elements, known as soil nailing and grouted ground anchors. The soil nailing and grouted ground anchors allow the execution of slopes on steep cuts and the walls are generally constructed from the top to down, permitting a better use of the space and lower cost (Ortigão and Palmeira, 1992). Soil nailing is an earth retention technique using grouted tension-resisting steel elements (nails) that can be designed for permanent or temporary support. The association of these elements with the local soil, with the wall face and with the drainage system, leading the slope to a higher - 1123 -