slope stability aspects and protective techniques...
TRANSCRIPT
Landslides
B. ChristarasSchool of Geology - Lab. of Engineering Geology & Hydrogeology
Aristotle University of Thessaloniki AUTH)
54006 Thessaloniki - Greece
Tel/fax: +30-31-0-998506, E-mail: [email protected]
Landslides
Methods of slope stabilization
• Controle of seepage forces• Reducing the driving forces and increasing the resisting forces
Drainage methods
• Deep wells,
• Vertical drains,
• Subhorizontal drains,
• Drainage galleries,
• Interceptor trench drains and
• Relief trenches.
Stabilization of the slopes
• Change of the slope geometry todecrease the driving forces or toincrease the resisting forces,
• Control of surface water infiltrationto reduce seepage forces,
• Control internal seepage to reducethe driving forces and to increasematerial strength,
• Provide retention to increase theresisting forces.
SUMMARY OF SLOPE TREATMENT METHODS FOR STABILIZATION
Treatment ConditionsGeneral purpose (preventive or
remedial)
CHANGE SLOPE GEOMETRY
Reduce height Rotational slides Prevent/treat during early stages
Reduce inclination All soil/rock Prevent/treat during early stages
Add weight to toe Soils Treat during early stages
CONTROL SURFACE WATER
Vegetation Soils Prevent
Seal cracks Soil/rock Prevent/treat during early stages
Drainage system Soil/decomposing rock Prevent/treat during early stages
CONTROL INTERNAL SEEPAGE
Deep wells Rock masses Temporary treatment
Vertical gravity drains Soil/rock Prevent/treat during early stages
Subhorizontal drains Soil/rock Prevent/treat-early to intermediate
stages
Galleries Rock/strong soils Prevent/treat during early stages
Relief wells or toe trenches Soils Treat during early stages
Interceptor trench drains Soils (cuts/fills) Prevent/treat during early stages
Blanket drains Soils (fills) Prevent
Electroosmosis* Soils (silts) Prevent/treat during early stages:
temporarily
Chemicals* Soils (clays) Prevent/treat during early stages
RETENTION
Concrete pedestals Rock overhang Prevent
Rock bolts Jointed or sheared rock Prevent/treat sliding slabs
Concrete straps and bolts Heavily jointed or soft rock Prevent
Cable anchors Dipping rock beds Prevent/treat during early stages
Wire meshes Steep rock slopes Contain falls
Concrete impact walls Moderate slopes Contain sliding or rolling blocks
Shotcrete Soft or jointed rock Prevent
Rock-filled buttress Strong soils/soft rock Prevent/treat during early stages
Gabion wall Strong soils/soft rock Prevent/treat during early stages
Crib wall Moderately strong soils Prevent
Reinforced earth wall Soils/decomposing rock Prevent
Concrete gravity walls Soils to rock Prevent
Anchored concrete curtain walls Soils/decomposing rock Prevent/treat-early to intermediate
stages
Bored or root piles Soils/decomposing rock Prevent/treat-early stages
*Provides strength increase
GEOLOGIC CONDITIONS AND TYPICAL FORMS OF SLOPE FAILURES
Geologic condition Typical movement forms
Rock masses: general Falls and topples from support loss
Wedge failure along joints, or joints, shears, and
bedding
Block glides along joints and shears
Planar slide along joints and shears
Multiplanar failure along joint sets
Dry rock flow
Metamorphic rocks Slides along foliations
Sedimentary rocks Weathering degree has strong affect
Horizontal beds Rotational, or a general wedge through joints
and along bedding planes
Dipping beds Planar along bedding contacts; block glides on
beds from joint separation
Marine shales, clay shales Rotational, general wedge, or progressive
though joints and along mylonite seams
Residual and colluvial soils Depends on stratum thickness
Thick deposit Rotational, often progressive
Thin deposit over rock Debris slide, planar; debris avalanche
or flow
Alluvial soils Depends on soil type and structure
Cohesionless Runs and flows
Cohesive Rotational, or planar wedge
Stratified Rotational, or wedges, becoming lateral
spreading in fine-grained soils
Aeolian deposits Variable
Sand dunes or sheets Runs and flows
Loess Block glides; flows during earthquakes
Glacial deposits Variable
Till Rotational
Stratified drift Rotational
Lacustrine Rotational becoming progressive
Marine Rotational to progressive; rotational
becoming lateral spreading; flows
Stabilization of slopes
forcestoplingorSliding
forcestainingF
___
_Re
ForcesTopplingorSlidingForcestaining
Stability
____Re
Plane failure analysis
Rapid wedge failure analysis
Comprehensive wedge failure analysis
Toppling failure analysis
Slope stability analysis
Earth pressure
Rock-Pack calc
Safety factor (SF) calculation for a slope
a) Without tension crack b) With a water-filled tension crack
Symbol Parameter Dimensions
F Factor of safety against sliding along sheet joint Calculated
H Height of the overall slope or of each bench 60 m or 20 m respectively
ςf Angle of slope face, measured from horizontal 50
ςp Angle of failure surface, measured from horizontal 35
z Depth of tension crack Calculated (m)
zw Depth of water in tension crack or on failure surface Variable (m)
α γr γw Horizontal earthquake acceleration Unit weight of rock
Unit weight of water
0.08 g(proportion of g) 0.027
MN/m3 0.01 MN/m3
W A Weight of rock wedge resting on failure surface Base area
of wedge
Calculated (MN) Calculated
(m2)
U Uplift force due to water pressure on failure surface Calculated (MN)
V c Horizontal force due to water in tension crack Cohesive
strength along sliding surface
Calculated (MN) Variable
(MN/m2)
θ Friction angle of sliding surface Variable (degrees)
T Force applied by anchor system (if present) Specified (MN)
ζ Inclination of anchor, anti-clockwise from normal Specified (degrees)
Slope stability analysis. Safety factor calculation for plane failure.
Ra
Ra
W
S
niΦi
Νi
F = tanΦi / tanni
Wl
Ni
Na
A
N
S
EW
ni
Φi
O
Νa
Ν
b
Ν
iI
Ra
Rb
Ri
Qa
Qb
a
b
A
BUb
Ua
Wedge Safety factor calculation (SF)
Sliding along two planes intersections
Nb
B
Na
A
N
S
EW
Φini
Νi
Wl
b
a
i
F = tanΦi / tanni
Changing slope geometry (1)
Natural slopesHard massif rocks: Maximum slope angle and height is controlled by the concentration
and orientation of joints and by seepage. The critical angle for high slopes of hard,
massive rocks with random joint patterns and no seepage acting along the joints is about
70o (Terzaghi, 1962).
Interbedded sedimentary rocks: Extremely variable, depending upon rock type,
climate and bedding thickness as well as joint orientations and seepage conditions. Along
river valleys, natural excavation may have reduced stresses sufficiently to permit lateral
movement along bedding planes and produce bedding plane mylonite shear zones.
Clay shales: 8 to 15o, but often unstable. When interbedded with sandstones, 20 to 45o.
Residual soils: 30 to 40o, depending upon parent rock type and seepage.
Colluvium: 10 to 20o, and often unstable.
Loess: Often stands vertical to substantial heights.
Sands: Dry and clean, are stable at the angle of repose (η=θ)
Clays: Depends upon consistency, whether intact or fissured and the slope height.
Sand-clay mixtures: Often stable at angles greater than repose as long as seepage
forces are not excessive.
Changing slope geometry (2)
Cut slopes in RocksHard masses of igneous or metamorphic rocks widely jointed, are commonly cut
to 1H:4V (76o).
Hard rock masses with joints, shears, or bedding representing major discontinuities
and dipping downslope are excavated along the dip of the discontinuity, although all
material should be removed until the original slope is intercepted. If the dip is too
shallow for economical excavation, slabs can be retained with rock bolts.
Hard sedimentary rocks with bedding dipping vertically and perpendicularly to the
face or dipping into the face; or horizontally interbedded hard sandstones and shales
are often cut to 1H:4V but in this case, the shales should be protected from weathering
with shotcrete or gunite if they have expansive properties.
Clay shales, unless interbedded with sandstones, are often excavated to 6H:1V (9.5o).
Weathered of closely jointed masses (except clay shales and dipping major
discontinuities) require a reduction in inclination to between 1H:2V to 1H:1V (63 to
45o) depending on conditions, or require some form of retention.
Changing slope geometry (3)
Cut slopes in SoilsThin soil cover over rock: The soil should be removed or retained as the condition
is unstable.
Soil-rock transition (hard residual soils to weathered rock) are often excavated to
between 1H:2V to 1H:1V (63 to 45o) although potential failure along relict
discontinuities must be consibered.
Most soil formations are commonly cut to an average inclination of 2H:1V (26o)
but consideration must be given to seepage forces and other physical and
environmental factors to determine if retention is required. Slopes between benches
are usually steeper.
Soil cuts are normally designed with benches, especially for cuts over 8 to 10 m
high. Benches reduce the amount of excavation necessary to achieve lower
inclinations because the slope angle between benches may be increased.
Drains are installed as standard practice along the slopes and the benches to
control runoff.
RETAINING WALL CHARACTERISTICS
Wall type Description Comments
Rock-filled buttress Constructed of non degradable,
equidimensional rock fragments with at
least 50% between 30 to 100 cm and not
more than 10% passing 2-in sieve [Royster
(1979)].
Gradation is important to maintain free-
draining characteristics and high friction
angle, which combined with weight
provides retention. Capacity limited by
of approximately = 40o and space
available for construction.
Gabion wall Wire baskets, about 50 cm each side, are
filled with broken stone about 10 to 15 cm
across. Baskets are then stacked in rows.
Free-draining. Retention is obtained from
the stone weight and its interlocking and
frictional strength. Typical wall heights
are about 5 to 6 m, but capacity is
limited by .
Crib wall Constructed by forming interconnected
boxes from timber, precast concrete, or
metal members and then filling the boxes
with crushed stone or other coarse granular
material. Members are usually 2 m in
length.
Free-draining. Height of single wall is
limited to an amount twice the member
lenght. Doubling box sections in depth
increases heights. High walls are very
sensitive to transverse differential
settlements, and the weakness of cross
members precludes support of high
surcharge loads.
Reinforced earth walls A compacted backfill of select fill is placed
as metal strips, called ties, are embedded
in the fill to resist tensile forces. The strips
are attached to a thin outer skin of precast
concrete panels to retain the face.
Free-draining and tolerant of different
settlements, they can have high capacity
and have been constructed to heights of
at least 18 m. Relatively large space is
required for the wall.
Concrete gravity wall A mass of plain concrete. Requires weep holes, free-draining
backfill, large excavation. Can take no
tensile stresses and is uneconomical for
high walls.
Semigravity concrete wall Small amount of reinforcing steel is used
to reduce concrete volume and provide
capacity for greater heights.
Requires weep holes, free-draining
backfill, and large excavation. Has been
constructed to heights of 32 m [Kullhawy
(1974)]
Cantilever wall Reinforced concrete with a stem connected
to the base. The weight of earth acting on
the heel is added to the weight of the
concrete to provide resistance.
Requires weep holes and free-draining
backfill; smaller excavation than gravity
walls but limited to heights of about 8 m
because of inherent weakness of the
stem-base connection.
RETAINING WALL CHARACTERISTICS (Continued)
Wall type Description Comments
Counterfort wall A cantilever wall strengthened by the
addition of counterforts.
Used for wall heights over 6 to 8 m.
Buttress wall Similar to counterfort walls except that the
vertical braces are placed on the face of the
wall rather than on the backfill side.
As per cantilever and counterfort walls.
Anchored reinforced-concrete
curtain wall
A thin wall of reinforced concrete is tied
back with anchors to cause the slope and
wall to act as a retaining system.
Constructed in the slope from the top
down in sections to provide continuous
retention of the slope during
construction. (All other walls require an
excavation which remains open while the
wall is erected.) Retention capacity is
high and they have been used to support
cuts in residual soils over 25 m in height.
Drains are installed through the wall into
the slope.
Anchored steel sheet-
pile wall
Sheet piles driven or placed in an
excavated slope and tied back with anchors
to form a flexible wall.
Seldom used to retain slopes because of
its tendency to deflect and corrode and
its costs, although it has been used
successfully to retain a slope toe in
conjunction with other stabilization
methods.
Bored piles Bored piles have been used on occasion to
stabilize failed slopes during initial stages
and cut slopes.
Height is limited by pile capacity in
bending. Site access required for large
drill rig unless holes are hand-excavated.
Root piles Three-dimensional lattice of small-
diameter, cast-in-place, reinforced-concrete
piles, closely spaced to reinforce the earth
mass.
Trade name “Fondedile” A retaining
structure installed without excavation.
Site access for large equipment required.
Rock Slopes
The various methods of retaining hard rock slopes are described briefly below.
Concrete pedestals are used to support overhangs, where their removal is not practical because of
danger to existed construction downslope.
Rock bolts are used to reinforce jointed rock masses or slabs on a sloping surface.
Concrete straps and rock bolts are used to support loose or soft rock zones or to reduce the number
of bolts.
Cable anchors are used to reinforce thick rock masses.
Wire meshes, hung on a slope, restrict falling blocks to movements along the face.
Concrete impact walls are constructed along lower slopes to contain falling or sliding blocks or
deflect them away from structures.
Shotcrete is used to reinforce loose fractured rock, or to prevent weathering or slaking of shales or
other soft rocks, especially where interbedded with more resistant rocks.
Gunite is similar to shotcrete except that the aggregate is smaller.
Retaining wall characteristics
Methods of retaining hard rock slopes
• Concrete pedestale, for overhangs• Rock bolt for jointed masses,• Bolts and concrete straps for intensely
jointed masses,• Cable anchors to increase support
depth,• Wire mesh to constrain falls,• Impact walls to deflect or contain
rolling blocks,• Shotcrete to reinforce loose rock, with
bolts and drains,• Shotcrete to retard weathering and
slaking of shales.
Egnatia Highway
Palio-Kavala
Egnatia Highway – Palio, Kavala
J2
J3
J1
F3
F1
J1: 224/68J2: 126/67
J3: 112/41
F1: 228/67
F3: 104/74
Sl
Egnatia Highway – Palio, Kavala
Έληππν θαηαγξαθήο επηηόπνπ ζηνηρείσλ (Bieniawski, 1979)
Έξγν:
Πεξηνρή:
Ζκεξνκελία:
ΔΓΝΑΤΙΑ ΟΓΟΣ – Όξπγκα Ο7
Γπηηθό πξαλέο (1ε αλαβαζκίδα)
Τκήκα 14/5 – 14/9
Ννέκβξηνο 1997
Γεσηεθηνληθή δώλε
Μάδα Ρνδόπεο
Δίδνο βξαρνκάδαο
Γξαλνδηνξίηεο
ΠΟΗΟΣΖΣΑ ΠΔΣΡΩΜΑΣΟ (R.Q.D.) ΚΑΣΑΣΑΖ ΣΟΗΥΩΜΑΣΩΝ ΑΤΝΔΥΔΗΩΝ
Δμαηξεηηθή
Καιή
Μέηξηα
Πησρή
Πνιύ πησρή
90-100 %
75- 90 %
50- 75 %
25- 50 %
< 25 %
+ (78)
Τγηέο πέηξσκα
Διαθξά απνζαζξσκέλν
Μέηξηα απνζαζξσκέλν
Σειείσο απνζαζξσκέλν
Παξακέλνλ έδαθνο
+ (14/5-14/6)
+ (14/7-14/9)
+ (14/6-14/7)
ΤΠΟΓΔΗΑ ΝΔΡΑ ΑΝΣΟΥΖ ΣΟΤ ΤΛΗΚΟΤ ΣΟΤ ΠΔΣΡΩΜΑΣΟ
Δηζξνή γηα 10m
κήθνπο ζήξαγγαο
(lit/min)
Καηάηαμε
αληνρήο
Αληνρή
(MPa)
Γείθηεο ζεκεηα-
θήο θόξηηζεο
(MPa)
ή
πίεζε λεξνύ (kPa)
ή
Γεληθέο ζπλζήθεο : Ξεξό
Πνιύ πςειή
Τςειή +
Μέζε
Μέηξηα
Μηθξή
Πνιύ κηθξή
>250
100-250
50-100
25-50
5-25
1-5
>10
4-10
2-4
1-2
<1
ΑΠΟΣΑΖ ΑΤΝΔΥΔΗΩΝ
πζηήκαηα: I (J1) II (J3) III (J4) IV
Πνιύ κεγάιε
Μεγάιε
Μέηξηα
Μηθξή
Πνιύ κηθξή
>200 cm
60-200 cm
20-60 cm
6-20 cm
< 6 cm
+ (23)
+ (115)
+ (42)
ΓΗΔΤΘΤΝΖ ΚΑΗ ΚΛΗΖ ΑΤΝΔΥΔΗΩΝ
ύζηεκα Γηεύζπλζε κέγηζηεο θιίζεο (ν) Γσλία θιίζεο (
ν)
κέζε από έσο
Η
II
III
IV
213o
098o
318o
185o
070o
290o
235o
130o
345o
61o
24o
26o
ΚΑΣΑΣΑΖ ΑΤΝΔΥΔΗΩΝ
ύζηεκα : Η (J1) II (J3) III (J4) IV
ΜΖΚΟ ΔΠΔΚΣΑΖ
Πνιύ κηθξή
Μηθξή
Μέζε
Τςειή
Πνιύ πςειή
<1 m
1-3 m
3-10 m
10-20 m
>20 m
+
+
+
+
+
ΑΝΟΗΓΜΑ ΑΤΝΔΥΔΗΩΝ
Πνιύ θιεηζηέο
Κιεηζηέο
Μέηξηα αλνηρηέο
Αλνηρηέο
Πνιύ αλνηρηέο
< 0.1 mm
0.1-0.5mm
0.5-2.5 mm
2.5-10 mm
> 10 mm
+
+
+
+
+
+
ΣΡΑΥΤΣΖΣΑ ΚΑΗ ΚΤΜΑΣΩΖ
Πνιύ ηξαρεία
Σξαρεία
Διαθξά ηξαρεία
Λεία
Οιηζζαίλνπζα
+
+
+
+
ΤΛΗΚΟ ΠΛΖΡΩΖ
Δίδνο
Πάρνο
Τιηθό ζε ζιίςε (Mpa)
ΚΤΡΗΑ ΡΖΓΜΑΣΑ ΚΑΗ ΠΣΤΥΔ
Γίλεηαη ε ζέζε θαη ηα θύξηα γεσκεηξηθά ηνπο ζηνηρεία:
ηε ζέζε 14/5 εληνπίζηεθε επηθάλεηα ξήγκαηνο κε ζηνηρεία 142ν/82
ν (F2), κε επίπεδε, νμεηδσκέλε
επηθάλεηα θαη κε πδξνζεξκηθά εμαιινησκέλν γξαληηηθό πιηθό πιήξσζεο πάρνπο 1 m. ηελ ίδηα ζέζε
εληνπίζηεθε ξήγκα κε ζηνηρεία 084ν/75
ν (F5), κε επίπεδε, θαηνπηξηθή επηθάλεηα ρσξίο πιηθό πιήξσζεο.
Δπίζεο ξήγκα κε ζηνηρεία 226ν/68
ν (F1), κε επίπεδε επηθάλεηα θαη κέηξηα απνζαζξσκέλν πδξνζεξκηθά
εμαιινησκέλν απιηηηθό πιηθό πάρνπο 5 c m πεξίπνπ.
ηε ζέζε 14/7+04 εληνπίζηεθε επηθάλεηα ξήγκαηνο κε ζηνηρεία 225ν/82
ν (F1), κε επίπεδε επηθάλεηα κε
πιήξσο απνζαζξσκέλν θαη πδξνζεξκηθά εμαιινησκέλν γξαληηηθό (θανιίλεο) πιηθό πιήξσζεο πάρνπο 0,4
m.
ηε ζέζε 14/7+05 εληνπίζηεθε επηθάλεηα ξήγκαηνο κε ζηνηρεία 123ν/66
ν (F3), κε θπκαηνεηδή επηθάλεηα
πιήξσο απνζαζξσκέλε, κε άλνηγκα πεξίπνπ 10 cm ρσξίο πιηθό πιήξσζεο.
ΓΔΝΗΚΔ ΠΑΡΑΣΖΡΖΔΗ ΚΑΗ ΠΡΟΘΔΣΑ ΣΟΗΥΔΗΑ
Σαμηλόκεζε ηεο βξαρνκάδαο ζε ζρέζε κε ηελ βαζκνλόκεζε:
Βαζκνί RMR : 70
Καηάηαμε : ΗΗ
Υαξαθηεξηζκόο : Καιή
Egnatia Highway – Palio, Kavala
Γεσηερληθή ηαμηλόκεζε βξαρνκάδαο RMR (Bieniawski, 1989) – Πξνζαξκνγή γηα βξαρώδε πξαλή SMR (Romana, 1985).
A. ΣΑΞΗΝΟΜΖΖ ΚΑΗ ΒΑΘΜΟΝΟΜΖΖ ΣΩΝ ΠΑΡΑΜΔΣΡΩΝ
ΠΑΡΑΜΔΣΡΟ ΠΔΓΗΟ ΣΗΜΩΝ
1
Αληνρή
ζπκπαγνύο
Γείθηεο
ζεκεηαθήο
θόξηηζεο
>10 MPa 4-10 MPa 2-4 MPa 1-2 MPa
Πξνηηκάηαη
ε δνθηκή
κνλναμνληθήο
αληνρήο
πεηξώκαηνο
Αληνρή ζε
αλεκπόδ. Θιίςε
>250 MPa 100-250 MPa 50-100 MPa 25-50 MPa
5-25
MPa
1-5
MPa
<1
MPa
Βαζκνί 15 12 7 4 2 1 0
2 Πνηόηεηα πεηξώκαηνο RQD 90-100 % 75-90 % 50-75 % 25-50 % <25 %
Βαζκνί 20 17 13 8 3
3 Απόζηαζε αζπλερεηώλ >2 m 0.6-2.0 m 200-600 mm 60-200 mm <60 mm
Βαζκνί 20 15 10 8 5
4
Καηάζηαζε αζπλερεηώλ
(βιέπε D)
πνιύ ηξαρείο
επηθάλεηεο,
αζπλερείο,
ρσξίο
δηαρσξηζκό,
πγηή ηνηρώκαηα
ειαθξά ηξαρείο
επηθάλεηεο,
δηαρσξηζκόο
<1mm, ειαθξά
απνζαζξσκέλα
ηνηρώκαηα
ειαθξά ηξαρείο
επηθάλεηεο,
δηαρσξηζκόο
1mm, πνιύ
απνζαζξσκέλα
ηνηρώκαηα
επηθάλεηεο
νιίζζεζεο
ή πιηθό
πιήξσζεο <5mm
δηαρσξηζκόο 1-
5mm ζπλερείο
Μαιαθό πιηθό
πιήξσζεο >5mm
ή
δηαρσξηζκόο >5mm,
ζπλερείο
Βαζκνί 30 25 20 10 0
Δηζξνή αλά
10m κήθνο ζεξ.
(lit/min) θακία <10 10-25 25-125 >125
5 Τπόγεην
λεξό
Λόγνο πίεζεο
λεξνύ δηαθιαζ.
πξνο κέγηζηε
θύξηα ηάζε ζmax 0 <0.1 0.1-0.2 0.2-0.5 >0.5
Γεληθέο ζπλζή-
θεο πγξαζίαο εληειώο μεξό ύθπγξν πγξό ζηάγδελ ξνή
Βαζκνί 15 10 7 4 0
B. ΠΡΟΑΡΜΟΓΖ ΒΑΘΜΟΛΟΓΖΖ ΜΔ ΒΑΖ ΣΟΝ ΠΡΟΑΝΑΣΟΛΗΜΟ ΣΩΝ ΑΤΝΔΥΔΗΩΝ (Βιέπε E).
C. ΣΑΞΗΝΟΜΖΖ ΣΖ ΒΡΑΥΟΜΑΕΑ Δ ΥΔΖ ΜΔ ΣΖΝ ΒΑΘΜΟΝΟΜΖΖ.
Βαζκνί RMR 100-81 80-61 60-41 40-21 <21
Καηάηαμε I II III IV V
Υαξαθηεξηζκόο πνιύ θαιή θαιή κέηξηα πησρή πνιύ πησρή
D. ΟΓΖΓΗΔ ΓΗΑ ΣΖΝ ΣΑΞΗΝΟΜΖΖ ΣΖ ΚΑΣΑΣΑΖ ΣΩΝ ΑΤΝΔΥΔΗΩΝ (γξακκή Α.4).
Μήθνο αζπλερεηώλ (ζπλέρεηα)
Βαζκνί
< 1 m
6
1-3 m
4
3-10 m
2
10-20 m
1
> 20 m
0
Γηαρσξηζκόο (άλνηγκα)
Βαζκνί
Καλέλα
6
< 0.1 mm
5
0.1-1.0 mm
4
1-5 mm
1
> 5mm
0
Σξαρύηεηα
Βαζκνί
Πνιύ ηξαρείεο
6
Σξαρείεο
5
Διαθξά ηξαρείεο
3
Λείεο
1
Οιηζζαίλνπζεο
0
Τιηθό πιήξσζεο
Βαζκνί
Καλέλα
6
θιεξό < 5 mm
4
θιεξό > 5 mm
2
Μαιαθό < 5mm
2
Μαιαθό > 5 mm
0
Απνζάζξσζε ηνηρσκάησλ
Βαζκνί
Τγηέο
6
Διαθξά
απνζαζξσκέλν
5
Μέηξηα
απνζαζξσκέλν
3
Σειείσο
απνζαζξσκέλν
1
Απνζπληηζεκέλν
0
E. ΠΡΟΑΡΜΟΓΖ ΣΑΞΗΝΟΜΖΖ ΑΤΝΔΥΔΗΩΝ (Romana, 1985).
Πεξίπησζε Πνιύ επλντθή Δπλντθή Μέηξηα Γπζκελήο Πνιύ δπζκελήο
P
T
P/T
aj - as
aj - as - 180o
F1
> 30o
0,15
30o – 20o
0,40
20o – 10o
0,70
10o – 5o
0,85
< 5o
1,00
P
P
T
βj
F2
F2
< 20o
0,15
1
20o – 30o
0,40
1
30o – 35o
0,70
1
35o – 45o
0,85
1
> 45o
1,00
1
P
T
P/T
βj - βs
βj + βs
F3
> 10o
< 110o
0
10o – 0o
110o – 120o
-6
0o
> 120o
-25
0o – (-10o)
-50
< -10o
-60
P = Καηνιίζζεζε κε επίπεδε επηθάλεηα νιίζζεζεο (Plane failure)
T = Καηάπησζε κε αλαηξνπή (Toppling failure)
βs = Κιίζε πξαλνύο
as = Γηεύζπλζε θιίζεο πξαλνύο
aj = Γηεύζπλζε θιίζεο αζπλερεηώλ
βj = Κιίζε αζπλερεηώλ
F. ΠΡΟΑΡΜΟΓΖ ΣΑΞΗΝΟΜΖΖ ΑΤΝΔΥΔΗΩΝ (Romana, 1985).
Μέζνδνο εθζθαθήο Φπζηθό πξαλέο
(Natural slope)
Πξνξrεγκάησζε
(Presplitting)
Ήπηα αλαηίλαμε
(Smooth blasting)
πλήζεο αλαηίλαμε
(Regular blasting)
Διαηησκαηηθή
αλαηίλαμε
(Deficient blasting)
F4 + 15 + 10 + 8 0 - 8
SMR = RMR + (F1 x F2 x F3) + F4
G. ΠΡΟΩΡΗΝΖ ΠΔΡΗΓΡΑΦΖ ΚΛΑΔΩΝ S.M.R. (Slope Mass Rating).
Καηάηαμε V IV III II I
SMR 0 - 20 21 - 40 41 - 60 61 - 80 81 - 100
Πεξηγξαθή Πνιύ πησρή Πησρή Μέηξηα Καιή Πνιύ θαιή
Δπζηάζεηα Πνιύ αζηαζέο Αζηαζέο Μεξηθά επζηαζέο Δπζηαζέο Πιήξσο επζηαζέο
Αζηνρίεο Μεγάιεο επίπεδεο ή
ζαλ έδαθνο
Δπίπεδεο ή κεγάιεο
ζθήλεο
Μεξηθέο αζπλέρεηεο
ή πνιιέο ζθήλεο
Μεξηθά ηεκάρε
(blocks)
Κακκία
Αλαγθαία κέηξα
(ππνζηήξημε)
Δπαλεθζθαθή Δθηεηακέλε
δηόξζσζε
πζηεκαηηθή Σπραία Κακκία
Egnatia Highway – Palioa, Kavala
Rock mass description, according ISRM
Number Dip Dipdirection Quantity Type Location Spacing Surface Aperture Weathering Infilling(o) (
o) (m) index 1 (m) index 2
1 42 118 1 joint 0.15 0.3 2b failed f.w. empty
2 40 132 1 joint 0.15 0.3 2b failed f.w. empty
3 40 120 1 joint 0.15 0.3 2b failed f.w. empty
4 40 116 1 joint 0.15 0.3 2b failed f.w. empty
5 52 108 1 joint 0.15 0.3 2b failed f.w. empty
6 41 107 1 joint 0.15 0.3 2b failed f.w. empty
7 38 104 1 joint 0.15 0.3 2b failed f.w. empty
8 57 218 2 joint 0.15 0.21 3b closed oxidized empty
9 73 221 2 joint 0.15 0.21 3b closed oxidized empty
10 66 219 2 joint 0.15 0.21 3b closed oxidized empty
11 62 218 2 joint 0.15 0.21 3b closed oxidized empty
12 60 221 1 joint 0.15 0.21 3b closed oxidized empty
13 58 225 1 joint 0.15 0.21 3b closed oxidized empty
14 63 216 2 joint 0.15 0.21 3b closed oxidized empty
15 65 232 1 joint 0.15 0.21 3b 0.15 oxidized aplite
16 70 131 1 joint 0.15 0.3 2b closed f.w. empty
17 40 118 1 joint 0.15 0.3 2b closed f.w. empty
18 75 134 1 joint 0.15 0.3 2b closed f.w. empty
19 70 228 3 joint 0.13 0.21 3b closed m.w. mylonite
20 73 221 2 joint 0.13 0.21 3b closed m.w. empty
21 75 225 2 joint 0.13 0.21 3b closed m.w. empty
22 75 223 3 joint 0.13 0.21 3b closed m.w. empty
23 70 220 3 joint 0.13 0.21 3b closed m.w. empty
24 60 128 1 joint 0.13 10 3b 0.001 s.w. empty
25 65 228 3 joint 0.07 0.166 3b closed s.w. empty
26 65 225 2 joint 0.07 0.166 3b closed s.w. empty
KAVALA - SLOPE 07
Tectonic measurements of road slope face
Discontinuities' characteristics
Left slope (west) - Road
f.
f.w.
s.w.
m.w.
h.w.
c.w.
r.s.
INDEX 1
ROUGHNESS-WAVINESS
a. Rough
b. Smooth
c. Slickensided
INDEX 2
1. Graduated
2. Undulating
3. Planar
Residual soil
Completely weathered
A- first order B- second order
Slightly weathered
Moderately weathered
Highly weathered
WEATHERING CLASSIFICATION
Fresh
Faintly weathered
• Biotitic gneiss with pygmatitic intercalations
(Serbomacedonian zone)
Rock cut in “Nimphopetra – Redina part” of Egnatia highway
(ch.25+215,89 – ch.25+373,95), to the East of Thessaloniki
Joints:
a) J1: 134/66 (slightly rough surfaces, spacing of
5-35cm)
b) J2: 35752 (slightly rough surfaces with spacing
of 3-50cm
Schistosity: S: 221/36 (slightly rough surfaces
with spacing of 3-15cm)
Fault: F: 195/60 (normal fault, joints with smooth
planar surfaces and
spacing of 10-50cm)
Geotechnical classification RMRStrength of intact rock 5-25MPa 2
RQD 25-50% 5
Spacing of discontinuities <60mm 5
Condition of discontinuities Length = >20mm
Separation = >5mm
Roughness = Slickenside
Infilling = >5mm, soft filling
Highly weathered
3
Ground water Completely dry 15
Rating adjustment for discontinuity orientations
Unfavorable -50
33-50 = 17
Potential sliding analysis
• Slope failure consisting by rockmass material
i. Sliding along schistosity surfaces 221/36 when slope inclination is more than 36o
ii. Potential wedge’s sliding; F=4,18
• Slope failure consisting by absolutely weathered rockmass material which behaves like soil
( γ = 2,65gr/cm3, φ = 22ο)
i. Slope stability without embakment: Sfsat = 1, Sfuns = 2
ii. Slope stability with embankment:
Sfsat = 1, Sfuns = 2
“Nimphopetra – Redina part” of Egnatia highway
Proposed slope excavation method
• Slope inclination less than 34o significant change to
morphology relief.
• Slope inclination equal to 34o moderate stability, wire
mess investment for protection to rock fall
• Proposed geometry: Two benches 10m high being
inclined to 34o, embankment formed by sort vertical
benches 10m width and 2,5m – 3,25m high form
downstairs
Kithira Island – landslide – site Kapsali
Mechanical behaviour of marls
• Seismic area: M: 7,2 (1750, 1903), M:6.0-6.8 (1789, 1866, 1937)
• According to lab test:
– the marl behaves like a soil been characterized as a silty clay of lowplasticity (CL-ML) with θ= 23,20 and c= 0.227 Kg/cm2.
– The marl is hard in dry conditions but looses easily its cohesion, inwet conditions..
– The permeability of the marl is estimated ask=100xd102=100x0.0012=0.0001 mm/sec = 10-6 cm/sec.
– The minimum safety factor of the slope is estimated to FSmin: 1.05-1.3 (dry) and FS1= 0.993 & FS2= 0.958 (wet) (method used:Morgenstern & Price (1965))
• slope stability analysis result:
– Back analysis in marls: c= 4 kN/m2 θαη θ= 180.
– Moisture of marl, in rain conditions: 15%, and γ= 23 kN/m3
Site Kapsali
Western landslide
Δηθόλα 1. Aλάιπζε επζηάζεηαο ηνπ πξαλνύο ζηελ δπηηθή θαηνιίζζεζε, κε αληίζηξνθή κέζνδν
Eastern landslide
Δηθόλα 1. Aλάιπζε επζηάζεηαο ηνπ πξαλνύο ζηελ αλαηνιηθή θαηνιίζζεζε, κε αληίζηξνθή κέζνδν
Δηθόλα 1. Καηνιίζζεζε ζην θαηώηεξν ηκήκα ηεο πθηζηάκελεο (αλαηνιηθήο) θαηνιίζζεζεο 2.
Other unstable sites
Δηθόλα 1. Γπλεηηθή αζηάζεηα ηνπ πξαλνύο κεηαμύ ησλ θαηνιηζζήζεσλ (ηνκή Α1-Α2)
Δηθόλα 1. Πεξηζζόηεξνη θύθινη νιίζζεζεο κε ζπληειεζηέο αζθάιεηαο SF= 07-1.1, πνπ ραξαθηεξίδνπλ
αζηαζείο έσο νξηαθά επζηαζείο επηθάλεηεο.
Δηθόλα 1. Δπζηάζεηα ηεο κάξγαο ζε ζέζε δπηηθά ηεο δπηηθήο θαηνιίζζεζεο (ηνκή Β1-Β2)
Α1-Α2
Β1-Α2
Malakasi A
Malakasi B
Malakasi C
High cut slope
Malakasi C
TECTONIC FORMATIONS
• These “tectonic formations” concern
tectonic melanges having “chaos”
structures. The matrices of these melanges
are mainly consisted of shailes and pelites,
containing detached blocks of limestones
and deep sea sediments.
• Mechanically the above materials behave
differently in dry and in wet conditions. In
dry conditions, they behave like a rock,
while in wet conditions, they loose
rapidely their cohesion and their original
structure behaving like a satured soil.
MAIN FACTORS OF SLIDING
Area on the West of Metsovo Tunel
-Tectonic formation between Pindos and Ionian flysch
-Tectonics
-Geometry of the flysch
Area on the East of Metsovo Tunel
-Tectonic formation between the ophiolites and flysch
-Tectonics
-Geometry of the flysch
Anilio
Egnatia Highway - Pindos mountainCHRISTARAS B., ZOUROS N., MAKEDON Th., DIMITRIOU An.
Aristotle University of Thessaloniki, (AUTH)
Lab. of Engineering Geology & Hydrogeology
Tel/Fax: +30-31-998506, e-mail: [email protected]
•.CHRISTARAS, B., ZOUROS, N. & MAKEDON TH., (1994): Slope stability phenomena along the Egnatia highway. The part Ioannina-Metsovo, in Pindos mountain chain, Greece. 7th Cong.
I.A.E.G., Lisboa, pp. 3951-3958.
•.CHRISTARAS, B., ZOUROS, N. & MAKEDON, TH. (1995): Behaviour of Votonosi formation in Pindos mountain (Greece). XI ECSMFE’95, Copenhagen, Bull. of Danish Geotechn. Soc. 11,
pp. 723-728.
•.CHRISTARAS, B., ZOUROS, N., MAKEDON, TH. & DIMITRIOU, AN. (1996): Common mechanism of landslide creation along the under construction Egnatia highway, in Pindos mountain
range (N. Greece). 30th IGC, Beijing, v.17.
•.Christaras, B., Zouros, N., Makedon, Th. & Dimitriou, An. (1997): Adverse geotechnical conditions in road construction. Sections of the new Egnatia highway across Pindos mountain range (N.
Greece) Intern. Symp. of IAEG, “Engineering Geology and the Environment”, Athens, Balkema Publ. pp. 2639-2646
•.CHRISTARAS, B (1997): Landslides in iliolitic and marly formations. Examples from the North-western Greece. Engineering Geology, Elsevier, 47, pp. 57-69.
Landslides in Eptahori Village - Kastoria County
• The village is located at the toe of a marly steep slope
• Slope inclination 500-700.
• Rock falls from the overlying sanstones (blocks of 200-400 tn) because of the weathering of the underlain marl.
• Marl is strong in dry conditions while it looses its strength rapidly during rain conditions.
• Weathering causes nderxcavation at the base of the overlying sandstone
• Instability of the sanstone blocks
• Toppling of sandstone blocks toward the village
Measures decreasing the possibility of failure•Retention of the unstable blocks •Soil on the slope - vegetation•Control of surface water - DrainsMeasure to decrease the energy of falling blocks •Change of slope inclination (possibility is limited) with creation of berms•VegetationMeasure for trapping and restraining falling blocks (at the end of the village)•Construction of a deep trench•Construction of a wall to restrain the arriving blocks
Protective measure
Heavy rains and mass movements in loose volcanic formationsExamples from Sarno (Italy) and Lesvos island (Greece)
Argenos (Lesvos Island - Aegean Sea - Greece)
•The event: In February 1998, a landslide was occurred in Lesvos Island,
during a heavy rain (120 mm high in 12 hours).
•The Landslide: The landslide presents a horizontal length of 150 m,
causing vertical displacement of 0.8 m at the national road, which crosses
the landslide, in the middle. The slope, where the landslide occurred, has
an angle of 300 dipping to the NE. An important fault, striking NE-SW,
limits the landslide to the SE, down throwing the northwestern part.
•Mineralogy: The phenomenon occurred in the weathered upper parts of
volcanic formations, consisting of andesite-dacite laves. In this area, a
thick layer of screes, composed of weathering volcanic materials covers
the volcanic rocks. Mineralogically these weathered materials mainly
consist of montmorilonite, micas, feldspars and calcite.
•.Physical properties: According to the grains size analysis, the material
can be characterized as clayey sand. Gravels are also included, in low
quantity. The liquid limit of the sample from the scree was measured
LL=46 and the plasticity index PI=25. For the weathered volcanic
materials from the surrounding area, the liquid limit was measured
LL=48 and the plasticity index PI=29.
B. Christaras1, N. Zouros2 & P. Marinos3
1. Aristotle University of Thessaloniki (AUTH), 54006 Thessaloniki, Greece, e-mail:
2. Museum of Natural History, Lesvos Island, Greece, e-mail: [email protected] gr
3. National Technical University of Athens, Patission 42, 10682 Athens, Greece, e-mail:
•Water activity: An important water source is located at the bottom of the weathered
materials, in contact with the impermeable layers (bedrock). The landslide occurred
in this loose formation. The loose materials were over-saturated, during the heavy
rainfall. The impermeable layer at shallow depth did not permit the quick drainage of
the soil during the extreme rain conditions. The swelling of the montmorilonite,
induced by the presence of the water source at the bottom of the moved mass
accelerated the sliding by increasing the driving forces.
Failure on the road
The top of the landslide
Contact water source
The landslide continues downward
REFERENCESCHRISTARAS B., ZOUROS N. & MARINOS P. (2000). Heavy rain and mass movements in pyroclactic formations. Examples from Sarno (Italy) and Lesvos
Island (Greece). Geoeng2000, An International Conference on Geotechnical & Geological Engineering, Melbourne, SNES0398.PDF, in CD
•The event: On the 4th and 5th of May 1998, significant
“landslides” occurred in the region of Campania in Italy. The
area is located east of Naples and Vezuvius volcano.
The mud level rose to cover the roads and the ground floors of
the houses throughout the town, and covering the surrounding
area with a thick mud stratum. 160 people lost their lives
under the mud, in the town of Sarno. Moreover, a significant
number of houses were declared uninhabitable and some of
them were destroyed.
•Meteorological data: In the period between the 3rd and 6th of
May 1998, 100mm of rain fell with a recurrence interval of
10-15 years (monthly rainfall on April 1998: 150-200 mm).
in the morning of the 4th of May and in the afternoon of the
5th of May, the rainfall intensity was 10 mm/h (the average
rainfall intensity during the 3-day period of 4-6/5/1998 was 3
mm/h St. Pietro weather station - CNR, Italy).
•The landslides: The mass movements of pyroclastic deposits
and erosion volcanic materials were actually flows triggered
by the intense rainfall. The slopes dip up to 30o and the
ground surface of the populated area dips 5o on average.
•Physical properties: The earthflows were mainly sands. The
apparent dry unit weight for the loose pyroclastic materials is
9.81 KPa and that of the volcanic tuffs 14.7 KPa. The loose
surface pyroclastic materials have high permeability (10-3-10-5
m/s). This property contributed to the rapid liquefaction of the
materials. The rainwater that caused the liquefaction could not
infiltrate into the deeper, low permeability layers
Sarno (East of Napoli - Italy)
0.0001 0.001 0.01 0.1 1 10 100
Diameter (mm)
0
10
20
30
40
50
60
70
80
90
100
erosion materials
Sample 1
Sand
CLAYSILT
FINE MEDIUM COARSE
SANDFINE MEDIUM COARSE
GRAVELFINE COARSE
Similar mechanism with that of Lesvos island:
• Mass movements in saturated weathered volcanic materials, during extremely heavy rainfalls where the drainage (or seepage) capabilities were insufficient to control the inflow water.
•The grain size and plasticity appear to be important properties, which together with water content were responsible for the different behavior of earth materials and the slopes, between
the above mentioned cases, under over-saturated conditions. The presence of swelling minerals favors sliding instead of flow.
In Sarno: The material was loose pure sand, without any plasticity or cohesion. The heavy rain rapidly produced a flow of earth materials, which moved downstream, covering the
cultivated areas between the slope-foot and the populated region. In loose pure sand, the water content exceeds the liquid limit easily.
In Lesvos Island: The material was characterized as clayey sand, containing swelling minerals and presenting low (but enough) plasticity and enough cohesion. These properties create
an unstable slope with typical rotational slip before liquefaction and earthflow will be occurred. A tension crack, which opened in the head zone, as slide started to move, captured runoff
and increased infiltration. Small-scale flowslides were also appeared in the sliding mass area.
Landslide at chainage 18+900 of the
national road Kozani-Rimnio
Landslide at chainage 18+900 of the
national road Kozani-Rimnio
Tectonic was responsible for
the failure (SF<1)
Tectonic was responsible for
the failure (SF<1)
Not circle sliding (Bishop
method
Not circle sliding (Bishop
method, SF>1)
Physicomechanical properties of soil formationsPhysicomechanical properties of soil formations
sample Location
chainage
Soil description
(USCS)
γ m U LL PI GI Cc K σ
D1 17Silty sand (SM)
2.13 16 8 46 22 0 0.324 3 10-5
D2.1 19 Marl (ML) 1.84 33 2 91 42 37 0.729 9 10-8 26.5
D2.2 » Marl (CL-ML) 1.86 13 45 12 12 0.315 10-8 35
D2.3 » Silty sand (SM) 1.78 11 4 49 15 0 0.351 2 10-5
D2.4 » Anglomerate 1.92 5 16 6.3
10-4
D3.1 4.5 Clayey silt
(CL-ML)
4 33 46 10 11 0.324 1.6
10-10
D4.1 Kessaria Cohesive silt (ML) 1.62 63 15 15 0.477 10-8 8.5
D4.2 » Cohesive silt (ML) 1.74 35 10 75 39 38 0.585 8.1
10-9
9.0
D5 Kariditsa Clay (CH) 51 6 61 9 12 0.459 9 10-10
D6.1Krokos -
Ano KomiClayey silt
(CL-ML)
22 70 46 9 10 0.324 4 10-10
D6.2 » Clayey silt
(CL-ML)
22 94 44 11 11 0.306 2.3
10-10
D6.3 » Silt (ML) 1.72 18 47 45 12 0.315 6.4
10-8
D7 Kozani Silty clay (CL) 1.75 20 10 60 25 21 0.45 3.6
10-10
Achlada - Florina CountyUnstable slope in lignite mine
• Cohesiveless pure sand
(c=0, phi=380)
• Cohesiveless silty sand
(c=0, phi=32)
• Stability factor <<1
1tan
tanF
1tan
tan
2
1
tan
tanwF
Wet loosen soil
Dry loosen soil
Simonos Petra Monastery
FS: .93FS: .93
The Koutlomoussi MonasteryThe Koutlomoussi MonasteryStabilization measures
• It was built in the 11th century.
• parallel
• mgrained
thickfractured
• atthe
jointed
• piles
• It was built in the 11th century.
• Geology: Mica schist dipping parallelto the slope.
• The bedrock is covered by a 5-6 mthick weathered mantle (fine grainedmaterial) underlain by a 6-8 m thicktransitional zone of strongly fracturedand altered rock.
• Slip plane (dip: 5o-6o downslope, atdepth 20m): contact between theweathered mantle and the jointedbedrock.
• Stabilisation: reinforced concrete pileswith anchored bulkhead
The Stavronikita MonasteryThe Stavronikita Monastery
An important N-S fault
causes damage to the
wall of the North side of
the monument.
An important N-S fault
causes damage to the
wall of the North side of
the monument.
In order to retain this fractured rock mass, a
pattern of anchored rock bolts was used. The
weathered mantle was stabilised using a
pattern of piles of 10 m length
In order to retain this fractured rock mass, a
pattern of anchored rock-bolts was used. The
weathered mantle was stabilised using a
pattern of piles of 10 m length
Retaining measuresRetaining measures
The Archaeological site of Olympia
•It was one of the most important sanctuaries
of the ancient period, where pan-Hellenic
games called Olympic, were performed from
a very early period.
•With the Olympic Games, the ideal of noble
rivalry found its complete expression and for
many centuries forged the unity and peace of
the Greek world.
•It has not yet been established when people
first began worshipping at Olympia.
However, archaeological finds show that the
area was at least settled from the 3rd
millennium B.C. The most of the ruins are of
the 5-2th c. BC.
Olympia Archaeological site
The Bouleuterion, 6th-5th c. B.C.
The Gymnasium, 2th c. B.C.
The Palaestra, 3th c. B.C.The Temple of Ira, 7th c. B.C.
Geotechnical conditions•The archaeological site is limited to the north
by a steep hill slope, which is crossed by a
national road of heavy traffic.
•The slope (at the level of the archaeological
site) consists of fine-grained soil, classified as
silty clay to silty clayey sand of low plasticity.
•According to the grain size analysis of
representative specimens, the material is
composed of 22-17% clay, 43-80% silt and 35-
3% sand. The liquid limit of the above
specimens is LL=30-32%, the plastic limit is
PL=22 and the plasticity index is PI=8-10%.
•The material presents low permeability and drainage ability.
•In dry conditions: UCS= 5-15 Mpa, c=17-23.7 Kpa and θ= 5,2-110.
•In rain conditions: It looses rapidly its cohesion providing unstable
conditions and important earth pressures on the ancient rocky retaining wall
which lean downslope, under the pressure
Instability phenomena•Unstable conditions cause important earth
pressures on the ancient rocky wall.
•Lower part of the slope: S.F.=0.17.
m
m
m
National road
Archaeological Site
The instability is due to:
•the quality of the geo-material,
•the water activity and
•the presence of an important root system of trees,
which act negatively on the existed ancient
retaining wall.
•Stabilization of the slope minimizing the earth
pressure on the ancient retaining wall:
• Drainage of the slope,
•Removal of the roots of the trees at the lower part of the slope.
•A shallow vegetation retaining system could also improve the stability of the
upper parts of the hill-slope.
•The methods used for reinforcing the ancient retaining wall should be
adapted to the identity of the archaeological site.
Mac
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