Environmental Engineering Reference
In-Depth Information
Geological and geotechnical conditions of the Machico-caniçal
highway
V.c. Rodrigues, s.P.P. Rosa, J.a.M. Brito & c.J.o. Baião
Cenorgeo, Engenharia Geotécnica, Lda., Lisboa, Portugal
aBsTRacT: The Machico-caniçal highway, with 8 km long, is part of Madeira island development
program, connecting Funchal city to caniçal village trough a continuous highway along the islands south
coast. This highway crosses an extremely mountainous region, conditioned by the existence of two very
heterogeneous volcanic complexes, generally covered by unstable slope deposits or by deep alluvial depos-
its. Those geological conditions lead to the execution of a wide range of civil engineering works. This
paper presents the most relevant geological and geotechnical aspects identified along this highway, in
particular in what special engineering structures (tunnels, bridges and viaducts) and retaining walls were
concerned.
1
GeneRal laYoUT
chaRacTeRisTics anD MaJoR
ciVil enGineeRinG WoRks
special engineering structures (bridges and tunnels)
and retaining walls involved, detailed geotechni-
cal studies were carried out, based essentially on
detailed geological surface surveys and deep sur-
vey consisting on rotational boring.
Up to 146 borings were made to investigate the
8 km length of the highway, comprising a drilling
total of 3 071 m, which corresponds to 384 m of
drilling/km.
of all the drilling carried out, around 72% was
made for the surveying of special engineering struc-
tures (bridges and tunnels), whilst the remaining
28% concerned the highway itself and the retain-
ing walls. of the survey works carried out for spe-
cial engineering structures, an average of 203 m of
drilling/bridge (21 m/support) and around 233 m/
tunnel (144 m/km) were made.
The Machico-caniçal highway, constructed
between 2003 and 2004, is located on the eastern
side of the Madeira island, along the southern
coastline, and it constitutes the connecting stretch
between santa catarina airport and caniçal vil-
The stretch comprehended the construction of
eight tunnels, five of them double, and four double
bridges and viaducts (cenor & Grid, 2002-2003).
The tunnels had a total length of 9 750 m.
The bridges and viaducts comprised a total
length of 1144 m.
an important set of retaining structures were
also designed, with a total length of 2750 m,
1900 m corresponding to retaining structures
equal to or higher than 8 m (Pereira
et al
., 2004).
in Tables 1a, 1B and 1c are presented the major
characteristics of the special engineering structures
(tunnels, bridges and viaducts) and retaining struc-
tures with height equal to or higher than 8 m.
3
GeoloGical anD GeoTechnical
conDiTions
The highway crosses formations of the Post-
Miocene volcanic complex (β
2
) and Mio-Pliocene
The β
2
complex, of a substantially heterogene-
ous constitution, is formed by alternate layers of
basaltic lava flows and pyroclastic materials, usu-
ally interstratified, also intercalated with generally
less important layers of tuffs.
The β
1
complex, the oldest volcanic complex
occurring on the island, as also a very heterogene-
ous constitution and is formed by a chaotic pile of
coarse materials resulting from the projection of
angular blocks, volcanic bombs and flows encased,
2
FielD inVesTiGaTion
in the light of the unfavourable topographic condi-
tions, of the occurring geological conditions (which
were characterised by substantial heterogeneity
and the presence, throughout practically the entire
stretch, of thick and unstable slope deposits), of
the acquired experience in these types of forma-
tions and also of the significance and number of
