LANDSLIDES IN LITHUANIA
V. MARCINKEVIČIUS1, R.B. MIKŠYS2, V. MIKULĖNAS3
Geological Survey of Lithuania, Lt. 2600 Vilnius, st S. Konarsko 35, Lithuania
e-mail: 1vytautas.marcinkevicius@lgt.lt, 2bonifacas.miksys@lgt.lt , 3vidas.mikulenas@lgt.lt
Slope landsliding is the most important
engineering geological process on the territory
of Lithuania. There are known historical facts about
the slope failures starting with the 16th century.
These are landslides of Gediminas and Bekešas
hills in Vilnius. The Seredžius bricked church was
washed down by Nemunas River stream, and
collapsed into the valley 1829. The principal part
of large slope failures of the past are remained
unknown. Ca. 85–90 landslides have been studied
or described during the last century (1937 and
later). It is noteworthy mention, that about 60 
of landslides are fixed in Lithuania jointly.
Landslide studies in Lithuania started beginning
with the 19th century. Systematic engineering
geological research of slope failures in the city
of Kaunas was carried out by Prof. M.Kaveckis
since 1937. Engineers geologists from Kaunas
University of Technology (F.Norkus, A.Žiedelis,
P.Masiulis) performed research of slopes of the
largest rivers in Lithuania 1960–1964. Since 1966,
specialists from the Department of Hydrogeology
and Engineering geology of Vilnius University
perform study of landslides. R.Stulpinas,
R.B.Mikšys, V.Vaitiekūnas are interested with
a problem of archaeological monuments - hillforts slope stability and an application of engineering
means to stabilise these historical sites. Recently
specialists from the Geological Survey and Institute
of Geology are able to apply quantitative or
qualitative methods of landslide hazard assessment.
Landslides damage both natural and artificial
slopes. Natural: due shore abrasion of the Baltic
Sea, Kuršių Marios lagoon and lakes, bank
undercutting by artificial water reservoirs, erosion
of rivers and ravines, etc. Artificial: slopes in
excavations and causeways (roadbeds) of traffic
roads, walls of quarries of natural resources, slopes
of the largest dumps; slopes of archaeological
monuments. The landslide activity is related to
location of the largest cities (Vilnius, Kaunas,
Alytus and others) in the deep valleys of the largest
rivers Nemunas, Neris and others. Due to human
economic activity, with a construction on the slopes
and their nearest environment, the stability and
natural moisture balance of soils are often
disturbed. During these works, when the strength
properties and strength stress state of soil have
changed, landslides could occur on the already
urbanized areas. According to economical
significance and their danger (by significance for
the land-use), landslides could be subdivided into:
1. Urban areas; 2. Traffic roads; 3. Deposits
of natural resources; 4. Protected areas and
monuments; 5. Dumps of waste materials; 6. Other
economically significant territories.
Favourable engineering geological conditions
for the landslide occurrence (geological structure,
hydrogeological, geomorphological,technogenical),
generally effecting a whole complex of natural
environment, where the slope failures form and
develop are as follows:
geological structure - slope failures develop in the
series of Quaternary sediments, formed
of differently sized sand, sandy loam, loam and
clay. Landslides develop sometimes on the
traffic roads especially due to deformations
of peat and silt. The most unstable slopes are
composed of stripped clay characterised by
liquid plastic or soft plastic consistency, or
incompletely densed artificial grounds. Their
best examples are landslides of Kuksa, Tauragė,
Rašnava clay deposits, also Vilkpėdė in Vilnius
and Gandinga hillfort.
hydrogeological (and hydrological) –caused by
surface and underground water influence
conditioning changes in consistency and
strength parameters of clayey soils, or by
hydrogeodynamical
pressure,
or
when
a filtrational stream effects the soil in the basic
frontal part of slope. The last is very important
on
Lithuanian
territory,
because
hydrodynamical forces provoke the unstabillity
of slopes in the walls of natural resource
deposits. The influence of hydrogeological
factors is very often linked to suffosion process.
geomorphological – Slopes are unstable in the
natural geomorphological conditions due to
erosional and abrasional strips, where the basic
frontal part of slopes is washed out by water
stream, and the steepnes of slopes increases till
the stability limit.
technogenical – Landslides are happened in
Tonribis, Kuksa, Tauragė and Rašnava quarries
(pit) due to vibration, and on the areas of testing
exploitation. They also
occur during
construction works, when practically used
retaining-walls raise the local future changes of
hydrogeological conditions to become worse
parameters of soil strength. Very frequent
causes
are
an
increase
of slope stepness by digging-off of their lower
part, extra loading of slopes, damages in
a water-supply system, removal of vegetation on
slopes for building, etc.
The landslide research at the time being is
provided according to these topics:
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1) to stabilise the landsliding process hazard for
buildings, communications and for objects
of historical heritage; 2) for the needs of territorial
planning.
An ordinary means for slope stabilisation are
included for technical projects in most cases. Main
aim of all projects – to eliminate impacts and
causes might disturb a balance of slopes in most
simplified ways and with minimal tools. Means
applied most frequently in Lithuania for a replace
of slope balance with certain factor of safety are as
follows: 1. The angle of slope is decreased if it is
possible; 2. The embankments are constructed
at the base of erodable slopes; 3. The bases
of unstable slopes are loaded by additional ballast;
4. Intensive drainage of the landslide body;
5. The surface water stream is directed away to the
bottom of slope; 6. In case of hydrodynamical
pressure – necessary engineering means are applied
to minimize this factor.
When the landslides damage very important objects
or slopes slope failures develop in urban areas: 1.
Retaining-walls are built to hold an active ground
pressure; 2. Anchor systems are equipped
(reinforcement of former landslides at the slopes
of Gediminas hill in Vilnius and at the base
of Vytautas hill in Kaunas); 3. The terracing
of the slopes surface; 4. Construction
of installations for drainage; 5. Steel sheet pilling.
The modern concept: To use most simplified and
least expensive engineering and economic means
for the landslide stabilisation in Lithuania. They are
aimed not for a stop of certain processes, but to
direct the landslide development in that way, which
itself will eliminate their arising causes.
The engineering – geological invasion into
landslide processes have to stimulate a natural
rebuilt of slope stability. Moderate and delicately
includable functional constructions of natural
materials are devoted to neutralise principal
erosional factors and to direct the natural
development processes of slopes for a suppression
of dynamically active deformation hotbeds.
Becomes apparent regularity: The landslides
occur most frequently in places of distinctly
economically impacted natural environment.
The research topicality of slopes is nowadays
confirmed by a large landslide (ca. 50 000 m3
of ground have slided down according to
preliminary data – see photo fig.) occurred
suddenly late evening 11th August 2000 on the
factory site of Lithuanian capital. The losses apart
from the rebuilt work make up over 1 million USD.
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