Environmental Engineering Reference
In-Depth Information
Detailed studies and stabilization methods of volcanic rocky
slopes in coastal areas, canary islands, spain
a. lomoschitz & a. cilleros
Departmento de Ingeniería Civil, Universidad de Las Palmas de Gran Canaria, Spain
R. García-Ferrera
JOFRAHESA, S.L., Las Palmas de Gran Canaria, Spain
aBsTRacT: natural relief on mountainous volcanic islands has deep ravines, steep rocky slopes and
high coastal cliffs. Volcanic formations have very heterogeneous rocks and soils. Besides, civil and building
works sometimes include high cuts on the terrain and, as a result, many urban areas have been affected
by rock falls and landslides. We show two case studies of the canary islands: (1) Rock fall hazard study
and stabilization methods on los Teques slope, Mogán, southern Gran canaria island, and (2) Geologic-
geotechnical study for a footpath project in Morro Jable coastal cliff, Pájara, southern Fuerteventura
island. We conclude that sometimes classic methods of rock masses characterization are ineffective, while
detailed geological studies are the best way to define and evaluate unstable zones on the slopes and to
design the most convenient stabilization methods.
1
inTRoDUcTion
and geomechanical classification of volcanic
formations (e.g., González de Vallejo et al.,
2007, del Potro & hürlimann 2007); (c) strength
and deformability models to interpret the behav-
iour of volcanic rocks (kwasniewsky 2002, ser-
rano et al. 2002, 2007) and (d) case studies of
engineering projects and works (e.g., erichsen
2002, simic 2007).
in this chapter, two case studies of volcanic rock
Volcanic areas present an outstanding variety of
rock and soil materials in a relatively random pat-
tern. This wide diversity is a direct consequence
of the genesis of the material by a wide range of
volcanic activity and external factors which con-
trol eruption dynamics, transport, emplacement
and reworking of the material being generated
(del Potro & hürlimann 2007).
occasionally, simplified graphic profiles of vol-
canic formations have been used, showing an alter-
nance of lava flows, of middle to high strength,
and interbedded pyroclastic layers, of low strength
(serrano et al. 2008). Moreover, natural slopes of
volcanic layers are variable and sometimes they
have a conical spatial disposal (volcanic cones)
around central points of eruption. Besides, other
features have to be considered such as the exist-
ence of syngenetic cooling joints, which are previ-
ous to tectonic jointing (Blyth & de Freitas 1984,
schmincke 2004) and the influence of the strata
thickness on the bearing capacity of the terrain
and the stability of slopes (lomoschitz, 1996).
in recent years, many works have been done on
the geotechnical characterization and behaviour
of volcanic rocks. They are about four main topics:
(a) geomechanical characterization of intact rocks,
from massive lava flows to pyroclasts, which are
of a variety of geochemical compositions and tex-
tures (Rodríguez-losada et al. 2007a,b); (b) field
Figure 1. Map of the eastern canary islands, 100 km
off the northwest coast of africa, and location (polygons
1 and 2) of the two study cases.
