Environmental Engineering Reference
In-Depth Information
a.
construction of the anchored wall.
a.
General view of the tieback slopes.
b.
Details of a retaining wall
b.
General view of the portal.
Figure 3.
south Machico interchange.
Figure 4.
Western portal of the caniçal double tunnel.
Given that one of the major obstacles to the
implementation of the construction works was the
thickness of slope deposits which covered substantial
part of the highway, a geotechnical characterisation
of these deposits was carried out in order to better
understand their behaviour (Rosa et al. , 2004).
in the fine fraction, which controls the behav-
iour of these deposits, the lower percentage limit
which passed through the #200 mesh was around
66%, the lower limits below 2 mm and 2 µ were
22% and 38%, respectively.
it was also obtained liquidity limit (ll) values
between 56% and 122% and plasticity index (Pi) val-
ues between 21 and 80%. The water content (w) and
volume weight (γ) obtained were 28% and 18.4 kn/m 3 ,
respectively. For the particles density (G) values of
between 2.53 and 2.90 were obtained. sand equiva-
lent (se) ranged between 14 and 16%. analysis car-
ried out on the matrix using the x-ray diffraction
method showed that the clay fraction is essentially
comprised of montmorillonite (around 95%).
The undrained residual resistance was estimated
based on the parameters in terms of actual tensions
based on the Mohr-coulomb rupture criteria.
it was obtained cu res = 14 kPa for c' res = 0 kPa
and φ' res = 14°. however, to take into account the
favourable contribution of gravel and blocks and
the undulation of the rocky substrate, in terms
of resistance to sheering, it was considered that
favourable parameters could be adopted. as a
result of this analysis it was adopted c' res = 0 kPa
and φ' res = 16° and cu res = 20 kPa.
4
eXaMPles oF ciVil WoRks
aFFecTeD BY The sloPe DePosiTs
at the south Machico interchange, slope deposits
vary in depth, reaching more than 20 m in local-
ized areas.
in order to construct this interchange, a large
amount of retaining structures were built, resort-
ing to a wide range of solutions, in order to enable
the construction of the highway and the respective
connecting access roads to the existing regional
road ( Fig. 3 ) .
 
 
 
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