National Road 150 passes through the central region of Argentina and is part of a bi-oceanic corridor from Brazil to Chile. In Sierra de Valle Fertil it has traversed sedimentary rock formations where they have built five bridges and six tunnels. During construction, instabilities phenomena were seen in both tunnels and surface works. In tunnels different behaviors were observed on hard rock and soft rock. Slope instability processes include mass displacement and failures due to decompression generated by excavation. Some reported cases occurred during the execution of the work, including various types of failures. In many sectors, rock masses showed a high degree of weathering. Analyses for the design and mitigation actions undertaken are described. Details emerged in the foundation of the bridges that make the section also arise.

1. Introduction

The Sierra de Valle Fertil is located in the west of Argentina (San Juan province). It is crossed by the National Road 150. This road is a part of a bi-oceanic corridor that runs from Porto Alegre (Brazil) to La Serena (Chile) (figure 1) (Aceituno et al 2014).

This road sector has 40 km in length including six bidirectional road tunnels with a total length of 2000 meters and five bridges.

All tunnels have the same horseshoe shape cross section, 11.9 m wide and 8 m. high with an area of about 70 m2. Details can be found elsewhere [1].

Two of the bridges are arch bridges with about 60 m span width between abutments.

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