LANDSLIDES IN LITHUANIA - lgt.lt · PDF file17 LANDSLIDES IN LITHUANIA V. MARCINKEVICIUS 1,...
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17 LANDSLIDES IN LITHUANIA V. MARCINKEVICIUS 1 , R.B. MIKŠYS 2 , V. MIKULENAS 3 Geological Survey of Lithuania, Lt. 2600 Vilnius, st S. Konarsko 35, Lithuania e-mail: 1 [email protected], 2 [email protected] , 3 [email protected] 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 16 th 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 19 th 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.Vaitiekunas 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, Kuršiu 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, Taurage, Rašnava clay deposits, also Vilkpede 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, Taurage 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:
Transcript of LANDSLIDES IN LITHUANIA - lgt.lt · PDF file17 LANDSLIDES IN LITHUANIA V. MARCINKEVICIUS 1,...
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LANDSLIDES IN LITHUANIA
V. MARCINKEVICIUS1, R.B. MIKŠYS2, V. MIKULENAS3
Geological Survey of Lithuania, Lt. 2600 Vilnius, st S. Konarsko 35, Lithuaniae-mail: [email protected], [email protected] , [email protected]
Slope landsliding is the most importantengineering geological process on the territoryof Lithuania. There are known historical facts aboutthe slope failures starting with the 16th century.These are landslides of Gediminas and Bekešashills in Vilnius. The Seredžius bricked church waswashed down by Nemunas River stream, andcollapsed into the valley 1829. The principal partof large slope failures of the past are remainedunknown. Ca. 85–90 landslides have been studiedor described during the last century (1937 andlater). It is noteworthy mention, that about 60 %of landslides are fixed in Lithuania jointly.
Landslide studies in Lithuania started beginningwith the 19th century. Systematic engineeringgeological research of slope failures in the cityof Kaunas was carried out by Prof. M.Kaveckissince 1937. Engineers geologists from KaunasUniversity of Technology (F.Norkus, A.Žiedelis,P.Masiulis) performed research of slopes of thelargest rivers in Lithuania 1960–1964. Since 1966,specialists from the Department of Hydrogeologyand Engineering geology of Vilnius Universityperform study of landslides. R.Stulpinas,R.B.Mikšys, V.Vaitiekunas are interested witha problem of archaeological monuments - hillforts -slope stability and an application of engineeringmeans to stabilise these historical sites. Recentlyspecialists from the Geological Survey and Instituteof Geology are able to apply quantitative orqualitative methods of landslide hazard assessment.
Landslides damage both natural and artificialslopes. Natural: due shore abrasion of the BalticSea, Kuršiu Marios lagoon and lakes, bankundercutting by artificial water reservoirs, erosionof rivers and ravines, etc. Artificial: slopes inexcavations and causeways (roadbeds) of trafficroads, walls of quarries of natural resources, slopesof the largest dumps; slopes of archaeologicalmonuments. The landslide activity is related tolocation of the largest cities (Vilnius, Kaunas,Alytus and others) in the deep valleys of the largestrivers Nemunas, Neris and others. Due to humaneconomic activity, with a construction on the slopesand their nearest environment, the stability andnatural moisture balance of soils are oftendisturbed. During these works, when the strengthproperties and strength stress state of soil havechanged, landslides could occur on the alreadyurbanized areas. According to economicalsignificance and their danger (by significance forthe land-use), landslides could be subdivided into:1. Urban areas; 2. Traffic roads; 3. Depositsof natural resources; 4. Protected areas and
monuments; 5. Dumps of waste materials; 6. Othereconomically significant territories.
Favourable engineering geological conditionsfor the landslide occurrence (geological structure,hydrogeological, geomorphological,technogenical),generally effecting a whole complex of naturalenvironment, where the slope failures form anddevelop are as follows:geological structure - slope failures develop in the
series of Quaternary sediments, formedof differently sized sand, sandy loam, loam andclay. Landslides develop sometimes on thetraffic roads especially due to deformationsof peat and silt. The most unstable slopes arecomposed of stripped clay characterised byliquid plastic or soft plastic consistency, orincompletely densed artificial grounds. Theirbest examples are landslides of Kuksa, Taurage,Rašnava clay deposits, also Vilkpede in Vilniusand Gandinga hillfort.
hydrogeological (and hydrological) –caused bysurface and underground water influenceconditioning changes in consistency andstrength parameters of clayey soils, or byhydrogeodynamical pressure, or whena filtrational stream effects the soil in the basicfrontal part of slope. The last is very importanton Lithuanian territory, becausehydrodynamical forces provoke the unstabillityof slopes in the walls of natural resourcedeposits. The influence of hydrogeologicalfactors is very often linked to suffosion process.
geomorphological – Slopes are unstable in thenatural geomorphological conditions due toerosional and abrasional strips, where the basicfrontal part of slopes is washed out by waterstream, and the steepnes of slopes increases tillthe stability limit.
technogenical – Landslides are happened inTonribis, Kuksa, Taurage and Rašnava quarries(pit) due to vibration, and on the areas of testingexploitation. They also occur duringconstruction works, when practically usedretaining-walls raise the local future changes ofhydrogeological conditions to become worseparameters of soil strength. Very frequentcauses are an increaseof slope stepness by digging-off of their lowerpart, extra loading of slopes, damages ina water-supply system, removal of vegetation onslopes for building, etc.
The landslide research at the time being isprovided according to these topics:
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1) to stabilise the landsliding process hazard forbuildings, communications and for objectsof historical heritage; 2) for the needs of territorialplanning.
An ordinary means for slope stabilisation areincluded for technical projects in most cases. Mainaim of all projects – to eliminate impacts andcauses might disturb a balance of slopes in mostsimplified ways and with minimal tools. Meansapplied most frequently in Lithuania for a replaceof slope balance with certain factor of safety are asfollows: 1. The angle of slope is decreased if it ispossible; 2. The embankments are constructedat the base of erodable slopes; 3. The basesof unstable slopes are loaded by additional ballast;4. Intensive drainage of the landslide body;5. The surface water stream is directed away to thebottom of slope; 6. In case of hydrodynamicalpressure – necessary engineering means are appliedto minimize this factor.When the landslides damage very important objectsor slopes slope failures develop in urban areas: 1.Retaining-walls are built to hold an active groundpressure; 2. Anchor systems are equipped(reinforcement of former landslides at the slopesof Gediminas hill in Vilnius and at the baseof Vytautas hill in Kaunas); 3. The terracing
of the slopes surface; 4. Constructionof installations for drainage; 5. Steel sheet pilling.The modern concept: To use most simplified andleast expensive engineering and economic meansfor the landslide stabilisation in Lithuania. They areaimed not for a stop of certain processes, but todirect the landslide development in that way, whichitself will eliminate their arising causes.The engineering – geological invasion intolandslide processes have to stimulate a naturalrebuilt of slope stability. Moderate and delicatelyincludable functional constructions of naturalmaterials are devoted to neutralise principalerosional factors and to direct the naturaldevelopment processes of slopes for a suppressionof dynamically active deformation hotbeds.
Becomes apparent regularity: The landslidesoccur most frequently in places of distinctlyeconomically impacted natural environment.
The research topicality of slopes is nowadaysconfirmed by a large landslide (ca. 50 000 m3
of ground have slided down according topreliminary data – see photo fig.) occurredsuddenly late evening 11th August 2000 on thefactory site of Lithuanian capital. The losses apartfrom the rebuilt work make up over 1 million USD.
