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KOSOVA LANDSLIDE - ATYPICAL SANATION

AbstractThe paper describes the rehabilitation of the main road atthe Kosova site, where due to appearance of the samenamed landslide in May of 2014th has been significantdamage of the road and complete stopping of traffic.

Thanks to the fact that the landslide in the road zone hasstopped on the terrace of Bosna River, the originalapproach to the rehabilitation has been based on thepresence of deposited materials in the toe part oflandslide which presented counter-weight in the bottomof the slope and imposed as natural rehabilitationsolution. Existing landfill material had been additionallysecured by stone-drainage ribs in function of securing theshore, landslide’s toe, road’s trunk and slope of thecutting above the road, and road stabilization wasperformed in five lines of insurance.

Key words: atypical rehabilitation, five stabilization lines

IntroductionIn the period of extreme rainfall of May 2014 and thecatastrophic floods that have engulfed parts of countriesin the region (Bosnia and Herzegovina, Croatia, Serbia),on a slope above the main road M17 between Doboj andMaglaj, in a place Kosova activated are landslides whichlaunched mass volume of approximately 500 000 m3.

Figure 1 Landslide shape in relation to M17

Prior stateDetrusive (progressive) landslide caused the destructionof several buildings in the hamlet Sejmenovići, and toepart has done a significant damage to a road in about 120meters.

Figure 2 Objects caught by landslide

The traffic was completely stopped, and movements onthe road in the longitudinal and transverse directionamounted to more than 6 meters. The existing reinforcedconcrete wall from hill side is broken, partly overturnedand translational "pushed" to 5-10 in the direction ofsliding. Roadway is in the longitudinal and lateraldirection wavy cracked with dismembered and chaoticskew parts of asphalt.

Figure 3 View on moved part of main road

Landslide stopped on a river terrace under the road, nextto the bed of river Bosna, which’s watercourse is crossedwith limestone outcrops. Terrace and limestone on theleft bank stopped landslide due to the fact that theypractically represent the natural shock absorbers to themoving sliding body towards the river. They actedstabilizing, and in equal measure activated were soilmasses deposited along the coastal belt. They represented"counterweight" to the toe part of sliding body. Thesefacts determined and focused design solution tostabilization and rehabilitation of road.

Proceedings of the 2nd Regional Symposium on Landslides, Belgrade, 2015

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Figure 4 Landslide stopped in toe

Solution approachIn order of emergent of traffic, intervention approach wastaken to repairmen. Alternative relocation of the road onthe opposite side of the river or circumvent of themountain sides, marked an extensive investigation andpreparation of project documentation with the bridgeover the river or high cuts or a tunnel on the hillside,with an expensive and longtime construction. Therefore,the rest of the existing road area.

Geological conditions

Wider area of the terrain on landslide location iscomposed by Jurassic-Crataceous clastic-carbonate andUpper Cretaceous carbonate sediments.

Figure 5 Geological map of wider landslide area

Immediate geological base, or substrate to landslide ismade by Jurassic-Crataceous clastites on whom aredeveloped thick surface covers of elluvial-dilluvial and

colluvial type, mainly clayish, debris and fragmentedcomposition.

Relation of clayish and debris components in in cover arevery heterogeneous, which results in weak geomechanicalproperties.

Heterogeneous engineering-geological component ofmasses of cover on location, also results in variablehydrogeological characteristics, so the different porositystructure defines permeability and function of some partsof slope above the traffic road.

Causes of landslide

In circumstances of intense dampening and flooding, andwith elevation of groundwater level (as in May 2014th),clayey fractions have swollen and turned into liquid state,unstable state, and debris more permeable fractions havebecome ‘’corridors’’ for more free turbulent waterflowing, which altogether resulted in activation of slidingprocess and apperance of consequent type.

Besides that, by engineering-geological and geotechnicalterrain observations it has been seen that surfacematerials are subject to erosion and denudation, and alsowith lower saturation turn into liquid state. Therefore,sliding begun gradually from upper part and spreaded tolower parts of the slope, all to the road.

Investigation works

In given circumstances are done trial pits under thetraffic and behind the wall. It has been determined thatlimestone substrate is on a depth of around 4 m, and inthe zone behind the wall, is clayey debris, clay and rockfragments, with water under hydrostatic pressures.

Concepts of design solutions

Based on the engineering-geological analysis andgeotechnical observations and the results of researchwork analyzed are several possible solutions, namely::

• production of retaining walls (it was not applicable dueto the high force and reliance of walls on piles over longdistances);

• anchoring walls (also adversely solution, because thegeological substratum, or solid rock on the hillside liedeep in the hinterland, and should have a very largelength anchors);

• drainage slope (exclusively drainage could not stabilizethe ground, because the slopes in general disturbedlandslide, with reduced geotechnical characteristics) and

• combinations of counterweights with rock-drainingribs.

Alluvium – river teracce

Globotruncane and rudiste limestones,calcarenites and cherts (Turon and Senon)

Mainly conglomerates and coarse-grainedsandstones, breccias, marls and massivelimestones

Landslide contour

Proceedings of the 2nd Regional Symposium on Landslides, Belgrade, 2015

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The last version was adopted because remainingcounterweight of landfill soils on the terrace stoppedlandslide and he emerged as a natural solution. Existingmaterials landfill or existing counterweight and road areadditionally secured with three longitudinal rock-drainage ribs in the function of providing the coastalzone, the foot of the landfill and the slope of the cutabove the road, on which are also applied drainage ribs.

RehabilitationStabilization of the road was performed in five "lines"with elements of insurance:

1. insurance river Bosna consisted of rockfilling largeblocks of stone resting on a solid limestone (rocky)surface in the river bed, thus preventing erosion coast;

2. ensuring the landfill on the river terrace is derived withrock-drainage rib along the foot of the landfill with twostreams of the water, which prevented possibly latermoves of the mass landfill, as counterweight;

3. insurance along the lines of the former retaining wallwas presented with a longitudinal rock-drainage rib fordraining water with three-row concrete gabions over ribs;

4. ensuring the slope of the cutting is achieved by cross-drains whose end parts (as in previous drainageelements) laid under the existing and potential slidingsurfaces and

5. load of roadway construction resting on mass oflandslide foot is achieved by removing the upper parts ofthe landfill and the execution of cross-stone ribs on thesame grids which are laid and ribs on the slope, whichstructure has provided roadway as a complete solid zoneof required (large) capacity.

Figure 6 Rehabilitated road

Conclusion

Based on the presented solution, with investment of lessthan 1 mil. €, rehabilitation and stabilization of road, andthe establishment of traffic was carried out for less than amonth after the occurrence of landslides. Considerablesavings were made with durable functionality of the road.

Reference

Fund of professional-technical documentation, Design&QC SarajevoMain design of immediate intervention on road M17-005: Karuše –

Ozimica, km 9+050 – km 9+270 in order to enable road for trafficon landslide area in Kosova, Design&QC Sarajevo, 2014

Engineering geology, chosen chapters, Bašagić M. (2007), Civ. Fac.Un. Sarajevo, [ISBN 551.1/.4: 624] (075.8), 173 p.

Basic geological map, sheet Zavidovići M 1:100 000, SZG Beograd,1973

Rehabilitation of main road M17 on Kosova locality,Engineering-geological-geotechnical terms of rehabilitation,Report, Design&QC Sarajevo, 2014

Figure 7 Normal cross-section of rehabilitated road