Environmental Engineering Reference
In-Depth Information
Figure 5. layout of central emergency parking lay-bys
and connecting gallery for vehicles.
Figure 7.
overall view of western tunnel portal.
pyroclastic material. occasionally this complex is
intercalated with highly altered basaltic lava. The
β
2
volcanic complex is formed of alternating layers
of basaltic lava and irregularly interstratified pyro-
clastic breccia materials which are also intercalated
with episodic layers of volcanic tuff.
Based on the lithological and structural charac-
teristics of the crossed formations obtained dur-
ing the course of prospecting and characterisation
works, although performed only in the portal zones
given the high covering and length of the galleries,
as well as on the experience acquired monitoring
other civil works in formations with similar char-
acteristics, the geotechnical zoning of the bedrock
was carried out. Zones were defined covering all
foreseeable situations with each geotechnical zone
corresponding to a level of bedrock quality and
behaviour. This zoning covered 4 geotechnical
zones referred to as ZG1, ZG2, ZG3 and ZG4.
Geotechnical zone ZG1 was essentially com-
prised of compact basalts (βc) and compact
Figure 6. overall view of heavy vehicle parking lay-by
and connecting gallery for vehicles during impermeabili-
zation phase and after completion of secondary lining.
The β
1
volcanic complex is formed of a chaotic
pile of coarse materials resulting from angular
block projections, volcanic bombs and scoriae,
covered in a more or less developed fraction of fine
