The Hernani tunnel has a mine length of 749 m with an excavation section of some 120 m². It’s free section is 95 m².
The materials that were cut through correspond to rhythmic alternations of tabular banks with a centimetric and metricentric thickness, with a long lateral extension of loams, lutite rocks and loamy rock.
Excavation took place via perforation and blasting for the harder rocks(RMR>40) and the use of mechanical means such as the backhoe with hammer where the materials to be excavated were softer.
Various supports were applied in function of the quality of the materials excavated, including synthetic fibre projected cement, swellex pins, trusses and even installing micropile and certain sections.
