xviii european young geotechnical engineers’ conference
TRANSCRIPT
XVIII European Young Geotechnical Engineers’ Conference17-20 June 2007, Ancona, Italy
LANDSLIDE STABILIZATION BY MEANS OF DEEP DRAINAGE.
Andrea ThemeliAlbanian Geotechnical Society
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INTRODUCTIONThis study is related to sliding zone near Tepelena City in the
South of Albania. The landslide gains a specific importance because of its
closeness with the national roadway that connects the south of Albania with the capital Tirana.
1. Current Conditions of the Landslide.2. Geological and Geotechnical investigation.3. Causal Factors Leading to the Loss of Equilibrium, Mechanism
of Rupture and Recommended Measures.4. Hutchinson’s Method for the Deep Seated Instability
Improvement.5. The Optimization of the Deep Trench Drain System.6. Conclusions.7. Questions.
Topics:
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THE LANDSLIDE NEAR TEPELENA CITY.
CURRENT CONDITIONS
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Deflected Electric Pole
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Deflected Electric Poles
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‘IN SITU’ INVESTIGATIONS
LABORATORY TESTS
GEOLOGICAL AND GEOTECHNICAL STUDY OF THE SLIDING ZONE.
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THE MAP OF SLIDING ZONE NEAR TEPELENA CITY.
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GEOLOGICAL PROFILE OF SLIDING ZONE.
1.5
8.0
1.5
7
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PHYSICAL AND MECHANICAL PROPERTIES OF LAYERS.
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The Causal Factors Leading to the Loss of Equilibrium.
The deposits faced in the incline are rocks of low resistance against weathering phenomena.
This deposits, when fully saturated with water, lose their mechanical properties.
The phenomenon of erosion by the surface water is present.
The equilibrium of the slope is affected also from the erosion that Vjosa River creates at the toe of the slope.
The presence of the underground water during the most part of the year.
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Mechanism of Rupture.
We are dealing with a translational slide.which is characterized by some well determinedfailure surfaces in the interior of the slide’s body. This is an active consequent landslide.Different layers move downwards and regardingeach other. For analyzing the stability of the slope, the residual parameters of shear strength of the soils, will be used.
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The measures that must be taken for thestabilization of the zone.
Lowering the underground water level by means of drainage using sub horizontal ditches, which will reach to the most possible depth.
Removing the surface water from the sliding body by means of a perimeter concrete ditch.
Building some river barrages in order to protect the slope from the erosion of Vjosa River.
It is recommended to reconsider the existing engineering measures at both retaining walls, which have not been constructed according to technical specifications.
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HUTCHINSON’S METHOD FOR THE DEEP
SEATED INSTABILITY IMPROVEMENT.
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UNDERGROUND WATER TABLE REDUCTION.
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EFFICIENCY OF DRAINS
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THE FACTOR OF SAFETY .
( )ββγ
ϕβγγcossincos2
⋅⋅⋅⋅⋅⋅−⋅+
=z
tghzCF uuS
( )βγ
ϕγγtgz
tghzF uuS ⋅⋅
⋅⋅−⋅=
"' hhhu +=
( )ηη −=⇒−
= 1''o
o
o hhh
hh
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THE OPTIMIZATION OF THE DEEP TRENCH DRAINS SYSTEM
1.5
8.0
1.5
7
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WEAKEST POINT ASSESSMENT.
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THE OPTIMIZATION OF TRENCH DRAIN SYSTEM
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FACTOR OF SAFETY BEFORE AND AFTER THE INSTALLATION OF THE DRAINAGE SYSTEM.
COULUMN Fs(max. w.l.) Fs(min.w.l.)
1 1.05 1.407
2 0.95 1.217
3 1.11 1.388
4 0.91 1.147
5 1.08 1.261
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DEEP DRAINS.
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PLAN VIEW OF THE ZONE AND THE DRAINAGE SYSTEM.
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LONGITUDINAL PROFILE OF THE ZONE AND THE DRAINAGE SYSTEM
Shtrese mbrojtese
Materjal drenues
Sheshim me rereø 400 mm
Drainage Geocomposite Liner
ø 300 mm
ø 300mm
ø 300 mm
ø 300 mm
ø 300 mm5
4
3
6
6
6
6
6
7
1
1.5
8.0
1.5
LEGJENDA
2
1
7
3
5
4
6
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CROSS SECTION OF DRAINS.
ø 300 mm ø 300 mm
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Z = 136.594
Mbulese mbrojtese
Veshje me gjeotekstil
Rere
ø 300 mmø 300 mm
Rere
Veshje me gjeotekstil
Mbulese mbrojtese
ø 300 mm
Rere
Veshje me gjeotekstil
Mbulesa e filtrueshme
ø 300 mm
Rere
Veshje me gjeotekstil
Mbulese mbrojtese
ø 300 mm
Rere
veshje me gjeotekstil
Mbulese mbrojtese
ø 400 mm Rere
Veshje me gjeotekstil
Materjal i filtrueshem
Mbulese mbrojtese
ø 400 mmRere
veshje me gjeotekstil
Mbulese mbrojtese
X = 415096.056Y = 466633.192Zpro = 135.841
X = 415098.917Y = 466617.645Zpro = 136.813
X = 415106.348Y = 466604.611Zpro = 137.417
X = 415114.354Y = 466591.887Zpro = 137.711
X = 415122.360Y = 466579.162Zpro = 137.696
X = 415131.397Y = 466566.995Zpro = 137.365
Materjal i filtrueshem Materjal i filtrueshem Materjal i filtrueshem Materjal i filtrueshem
Materjal i filtrueshem
Drenazh grumbullues
Drenazhet gjatesore
CROSS SECTION OF DRAINS.
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ø 300 mm
SHTRESE GJEOTEKSTILI
VESHJE BETONI
RRJETE CELIKU (10 X 10 cm)
1.0
0.5 0.5 0.5
1.0
RRJETE TELI (10 X 10 cm)
VESHJE BETONI
SHTRESE GJEOTEKSTILI
1.50.3
0.5
0.7
0.5
0.08
0.08
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CONCLUSIONSThe failure was clearly triggered by the high
underground water table level. In these cases the dewatering of the ground is an inevitable remedial measure.A good method of dewatering the ground is the installation of underground sub-horizontal ditches.The optimization method of the deep trench drain system is shown in this presentation
Reference ListAtkinson, J. 1997. Geotecnica, meccanica delleterre e fondazioni.Bozo, L. 2001. Mirëmbajtja dhe rehabilitimi i rrugëve.Bozo, L. 2002. Bazamentet e objekteve të kultit në Shqipëri.Bozo, L. 2004. Dinamika e dherave (Pjesa II-të).Hutchinson, J.N. 1977. Assessment of the effectiveness of corrective measures in relation to geological conditions and types of slope movement. Bulletin of the Int. Assoc. Eng. Geol., 16, 131-155.Konomi, N. 2001. Gjeologjia inxhinerike (GjeodinamikaInxhinerike).
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ENDQuestions are welcomed