Environmental Engineering Reference
In-Depth Information
struction of six double tunnels inserted in the
Machico-caniçal expressway were presented.
in the referred expressway, the percentage
of tunnel length is unique, reaching 64% of the
total length, mainly due to vigorous relief of the
region.
emphasis was given to the caniçal Double
Tunnel, which figures as the most representative
and emblematic constructed along the Machico-
caniçal expressway.
concerning the design, although consider-
ing the significant limitations associated with the
nature of the volcanic rock mass, it was possible
to improve the geological recognition in order to
obtain the necessary guidelines to define the geo-
technical zoning.
it was also possible to estimate the temporary
support applying empirical methods and define the
soil characteristics required to the calculation mod-
els, consisting either by the finite element method,
or by the hyperstatic reactions method.
This was complemented with a thorough obser-
vation by a continuous geologic survey of the rock
mass, adapted to the development of the excava-
tions and with complementary boreholes, as well
as with measurements of displacements inside the
tunnels, at the surface or inside the surrounding
rock mass.
Therefore, it was possible to adapt the supports,
in effective time, to the effective conditions of the
rock mass. The observation design methodology
and supervision of the works proved to be rather
adequate and allowed a rational and safe adapta-
tion of the support, thus enabling a significant
economy during the construction stage.
Finally, reference was made to the integrated
control and safety system installed in the tunnels.
Figure 9.
overall view of eastern tunnel portal.
For the widened section, excavated in forma-
tions of alternate bands of basalt and disaggre-
gated breccia, the excavation was carried out using
a methodology similar to the one defined for the
parking lay-bys. Yet, due to the proximity of the
tunnel portal, reinforcement for the primary lin-
ing was studied. This consisted of the application
of heB180 steel ribs with 1 m spacing, associ-
ated with 15 cm of shotcrete incorporating aQ50
welded steel mesh.
in the current section, the secondary lining in
reinforced concrete had a constant thickness of
0.25 m and 0.40 m in accordance with the respec-
tive geotechnical zone which the tunnel was cross-
ing. Figures 7 & 9 depict the final aspect of the
tunnel portals.
auscultation consisted of measuring the following
installed instrumentation: i) precision topographic
marks set in profiles transverse to the galleries
ii) rod extensometers inserted in some of the pro-
files, with each one providing two reading points
located at 2.0 m and 5.0 m from the top of the vault;
iii) targets placed around the excavation edge in sec-
tions at distances of 25 m or 50 m for converging
readings; iv) sealed inclinometer tubes in bore holes.
Great emphasis was given to safety concerns
and an evolved system was implemented which
comprised the installation of the following con-
trol and safety equipments: power supply; light-
ing; ventilation; signs; communications; control
systems ccTV; auscultation; fire detection and
fire extinguisher systems; fire hydrants; emergency
parking lay-bys, connecting gallery and light vehi-
cle reversing and pedestrian evacuation galleries;
and access walkways for service personnel and
emergency personnel.
ReFeRences
Baiao, carlos J.o., costa, P., sousa, luis R., Rosa, sergio
P.P. 2003. caniçal Tunnel, island of Madeira Geo-
technical characterisation & observation. Jornadas
hispanolusas “obras subterraneas, Relevancia de la
Prospeccion y observacion Geotecnicas”. Madrid.
Brito, Jose a.M., costa, P., Monteiro, a., oliveira, R.,
Gaiao, R., sousa, luis R. 2002. Geotechnical analy-
sis of the caniçal Tunnel, island of Madeira. interna-
tional symposium isRM. eurock 2002. Madeira.
Brito, Jose a.M., Baiao, carlos J.o., Rosa, sergio P.P.
2005. Modernisation of the Roadway network of the
island of Madeira—Part 3: Tunnels engineering &
life Magazine. no.9.
cenor. 1991a. Variant to 101 expressway in Machico.
Geological-Geotechnical study.
cenor. 1991b. Tamega s/a—somague a/s construction
consortium Machico-caniçal expressway—1st Phase
Queimada stretch Tunnel to caniçal Basic Project.
implementation Project.
6
conclUsions
The main aspects related with the geological-
geotechnical survey, the design and the con-
