failures and landslides:
This term includes phenomena of partial or total
instability or failure of natural or manmade slopes.
Landslides may occur due to (a) the mineralogical
composition of the ground (presence of clay minerals), (b) the
presence of faults, especially when their dip is parallel to
that of the slope, (c) the dip of the sedimentary layers (parallel
to the dip of the slope), (d) frequent and heavy rainfall
resulting in erosion and mechanical weakness of the soil or
abrupt increase of the water table, (e) intensive groundwater
pumping resulting in lowering the water table, internal erosion
and reduction of the soil cohesion, and (f) earthquakes and
Cyprus, relatively large and active slope failures and
landslides occur in the western part of the island (Paphos
District), where rocks of the Mamonia Complex and the Kannaviou
Formation are exposed. Characteristic
examples of landslides are observed in the villages of Mamonia,
Kannaviou, Statos, Pentalia, Kritou Marottou, and Anadiou.
In the southern part of the island (Limassol District),
landslides relate chiefly to the Lower Marls of the Lefkara
Formation as well as the Moni Formation (bentonite).
Examples can be seen in the areas of the villages of
Kilani, Silikou, Doros, Korfi, Trimiklini as well as Moni and
Pentakomo. Also, in
northwest Cyprus, landslides can be observed along the roads
from Morphou to Skylloura and from Myrtou to Panagra.
long mining history of Cyprus has resulted in extensive waste
dumps in many areas such as Kalavasos in the south, Limni in the
northwest, Mitsero and Mathiatis in central Cyprus and Troulli
in the east. In all
these examples the waste dumps have been deposited without a
proper design. They are characterised by high porosity and high
compressibility, low density and limited strength.
Thus, under certain conditions the slopes of these dumps
may develop landslide phenomena.
number of measures can be taken either separately or in
conjunction with one another to face the problem of slope
failures and landslides. Such
measures include the decrease of the dip of the slope, the
unloading of the land-slit mass, the construction of berms or
terraces, the controlled pumping of ground water to maintain a
stable water table, the construction of drainage system and
retaining walls etc.
Rock falls are observed mainly in the mountainous areas
of Cyprus and in natural and manmade slopes.
They are mainly related to one or more causes according
to the geological, topographical and rainfall conditions.
Faults and fractures play an important role, especially
their density and network.
Earthquakes often contribute to the fracturing of the
rock mass and eventually to rock falls.
Rock falls directly affect the safety of the people.
Examples of rock falls have been observed in Lemithou,
Akrounta, Pelentri, Prodromos and along the road from Nicosia to
on the characteristics of each case of rock fall, different
measures can be taken to resolve the problem.
The most frequently used method for facing the problem is
the installation of anchors and rockbolts.
Settlement is the subsidence of a civil structure that is
caused by its weight and the relative compressibility and
deformation of the underlying soil.
Thus, foundation settlements are highly related to the
geological conditions and the mechanical properties of the
clays and gypsum are the main soil types in Cyprus that are
related to foundation settlements.
Cyprus, marls are found in different types according to their
geological age and lithological characteristics.
Marls are found either as thin interlayers in the Lefkara
and Pakhna Formations or as thick layers in the Athalassa and
Nicosia Formations. The
most extensive and significant type of marl, from the
geotechnical point of view, is that of the Nicosia Formation.
The mechanical behaviour of marl depends significantly on
its moisture and clay content.
Thus, the mechanical behaviour of marl is very sensitive
to the effects of water, which gives rise to swelling and
shrinkage phenomena leading to cracks in buildings.
clayey geological formations that contain the mineral
montmorillonite, and thus belonging to the bentonitic soils, are
characterised by high plasticity and swelling as well as
shrinkage under certain water-content conditions.
In summer, for example, they shrink due to dryness and
cause volume reduction leading again to the development of
cracks in civil structures.
In winter, on the other hand, they expand (swelling
effect) due to the absorption of water and become more plastic
which reduces their strength and increases their compressibility.
most characteristic swelling clays in Cyprus belong to the
Kannaviou and Moni Formations (bentonitic clays), although the
Lower Marls of the Lefkara Formation also exhibit significant
swelling properties. The
problems that are related to swelling clays are mainly seasonal
movements of buildings (subsidence and lifting) and other linear
civil structures such as roads and drainage systems.
Swelling clay effects are observed in areas around the
villages of Pentakomo, Moni, Kannaviou, Kritou Marottou,
Pentalia, Marathounta, Nata, Kythrea, Myrtou, Gastria and
landslides are observed in areas that are composed of bentonitic
solution to the problems relating to foundation settlements due
to the presence of marls or bentonitic clays is difficult,
expensive and often of limited effectiveness.
The main remedy includes measures to ensure stable
moisture content on the foundation level.
Raft foundation is also designed as well as pilling.
settlements or subsidence of civil structures can also be caused
by the development of void spaces or caves in the ground called
Cyprus, sinkholes are formed in lithological units that contain
either gypsum or limestone and they are the products of the
dissolution of these two lithologies by water.
Sinkholes in gypsum occur all over the island, in
particular in the areas of Pissouri, Maroni, Aradippou, Kathikas,
Kalavasos, Nisou, Pergamos and between Lefka and Galinoporni.
The sinkholes are rather small in size, may have an
irregular shape and constitute foundation “traps”.
When their roof collapses due to the weight of the civil
structure on top, sinkholes may cause subsidence problems.
Remedial measures are often very difficult and include
filling up the sinkhole with grout.
Limestone is another rock type that sinkholes or caves can be developed in due to its dissolution by water. In Cyprus, the dissolution of limestones appears to be rather limited, forming small, irregular surface caves or complex underground voids and drainage systems leading to the development of karstic springs (karst is a term derived from the Carso area in the Dalmatian Alps in Yugoslavia relating to rock dissolution). Such karstic springs are found in the northern part of the island along the Pentadaktylos Range. Underground dissolution voids are difficult to identify from the surface and constitute a serious potential problem in the stability of civil structures.