Environmental Engineering Reference
In-Depth Information
cliff stabilization solutions at the south coast of Madeira island
V.c. Rodrigues, F.a. sousa, s.P.P. Rosa & J.M. Brito
Cenorgeo, Engenharia Geotécnica, Lda., Lisboa, Portugal
aBsTRacT: The necessity to protect important infrastructures constructed, along the south coast of
Madeira island, at the top and at the bottom of high cliffs, against the collapse of isolated rock blocks
or of significant masses of soil and rock debris, has lead to the development of complex geotechnical
projects and to the execution of specific stabilization works. This paper describes, for some of those cliffs,
the existing geological conditions and the main instabilization processes that affect them. attending to
the acquired experience from these works, some considerations are presented about the advantages and
limitations of the stabilization solutions considered, especially in what concerns the required logistics for
their execution.
1
GeneRal chaRacTeRisTics
oF The cliFFs
2
GeoloGical chaRacTeRisTics
The south coast of Madeira island presents a very
accentuated relief, formed by deep valleys and
elongated mountains known as “lombos”.
These elevations are, in most cases, cut by
subvertical cliffs, usually over hundred metres
height, originated in the Post-Miocene Volcanic
This complex is constituted of alternating lay-
ers of basaltic lava flows and breccias. interstrati-
fied in these formations also occur tuffs layers,
with lenticular and irregular contours, generally
of minor expression (serviços Geológicos de
Portugal, 1974).
The basaltic lava flows can be either compact
(βc) or fractured (βF) exhibiting, mainly, subver-
tical contractional joints, showing continuity and
along Madeira island south coast, between arco
da calheta and Machico, there are several cliffs
of significant height showing stability problems,
threatening the safety of the infrastructure located
at their top or bottom.
as a consequence, some of these infrastruc-
tures had their use or occupation conditioned or
interdicted.
over the last years, several cliffs have been iden-
tified as requiring stabilization works involving
significant human and material resources.
Table 1 presents the characteristics of the
most important cliffs that were already stabilized,
namely its location, length, height and cost of the
stabilization works.
Table 1. Main characteristics of the most important cliffs stabilized along Madeira island
south coast.
Maximum
height
(m)
length
(m)
cost
(€)
location
Description
arco da calheta
cliff above the eR101
at sítio do Massapez
150
50
2.0 × 10
6
Ponta do sol
cliff above the eR222
at sítio da Vargem
40
40
0.7 × 10
6
Ponta do sol
Upper section of the
cliff above the lugar
de Baixo seaport
200
60
7.2 × 10
6
Ribeira Brava
cliff above the eR222
at sítio do calvário
50
20
0.3 × 10
6
Machico
cliffs beneath the saint
João Baptista Fort
45 to 50
10 to 20
0.2 × 10
6
