Determination of the stress state in the Andean Cordillera Frontal near the border between Argentina and Chile

MARTINO, ROBERTO DONATO; GIAMBASTIANI, MAURICIO; ROCCA, RICARDO J.; GUERESCHI, ALINA BEATRIZ; HUERTA SOAJE, PEDRO J.; MARCET, JUAN E.

Buenos Aires

Congreso; 8th South American Congress on Rock Mechanics; 2015

Sociedad Argentina de Ingeniería Geotécnica

The initial state of stress is an important parameter in underground excavations. From its knowledge, it is possible to calculate the stresses induced around the excavation and the necessary support for stabilization. This task becomes critical when the excavations have great dimensions such as caverns and when rock overburden is significant. Different methodologies are discussed, including simple regional stress maps, the survey of surface paleostress and hydraulic fracturing executed in borehole between 500 and 800 m deph. These methodologies have been applied in the Andean Cordillera Frontal, where the Agua Negra tunnel will be built between Argentina and Chile. This area is affected by the subduction of the Nazca plate beneath the South American plate. This setting generates that the greatest principal stress σ1 has a W-E orientation and relationship with the vertical stress (σ2) reaches about 1.4.