The main characteristics of the design and construction of the Pestana Júnior Tunnel, which was built in Funchal (Madeira Island) from the Cota 200 road to the Pestana Júnior road and Campo da Barca are and described. In the design stage, the new Austrian Tunneling Method was applied, and in the geological-geotechnical study of the rock mass, the Bieniawski pro mechanical classification was used with the necessary modifications, due to the peculiar properties of the basaltic rock mass. The tunnel was inaugurated and started functioning in November 1997.
The Pestana Júnior Tunnel develops, approximately, between kms 1+665 and 1+892 of the connection road between the Cota 200 road and the Pestana Júnior road and Campo da Barca, with a 227 m length. The cross-sections geometrical characteristics are identical to the ones of road plan (Figs 1,5). The cross-section is composed by an horizontally elongated and inferiorly truncated ellipsis, so that the gabarit would be respected, with a rectangular section of 4,5 m height, considering the road transverse inclination, and prolonged by two small vertical fragments, with variable heights, dependent on the superelevation of the cross-section. The road is formed by three lanes with 3,50 m width each, one descendent and two ascendant (one destined to fast traffic and the other to slow traffic) and by two trief and lateral with a total width of 0,50 m (Fig. 2). The side walls were painted with white paint on a 2,5 m height, above the sidewalks, to improve visibility conditions inside the tunnel. The longitudinal profile by the tunnels directress presents an ascendant pendent, diminishing from east to west, from approximately 13% to 5% and the cross-sections have superelevations to which correspond pendants between +5% and - 4%.
Twelve geological boreholes were executed for the rock mass recognition from which it was possible to preview that the Pestana Junior tunnel would be excavated on an essentially basaltic rock mass, except on the portal zones where could occur thin lenticular layers of compact and disagregated breccias, fractured and disagregated basalts and weathered volcanic tuffs. The thick basalts correspond to the most representative geological formation along the tunnel and concern very thick basaltic rocks, of high resistance, with gradual variation to vacuolar basalts, from slightly to very vacuolar and more or less breccious. The excavated sections were correspondent to the serviceable sections increased by a thickness of 30+5 cm, so that the concrete lining was not inferior to 25 cm and not significantly superior to 35 cm. For measurement it was considered a medium thickness of 30 cm. In the areas corresponding to the extremities of the tunnel, the indicated thickness was increased by 10 cm, keeping the same tolerance range. On the west portal it was constructed a cut-and-cover tunnel, on a 21 m length, with the temporary detouring of the Luso-Brasileira road that crossed the tunnel on an upper level.