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: christar@geo.auth.gr

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: christar@geo.auth.gr

•.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:

christar@geo.auth.gr

2. Museum of Natural History, Lesvos Island, Greece, e-mail: n.zouros@geo.aegean gr

3. National Technical University of Athens, Patission 42, 10682 Athens, Greece, e-mail:

marinos@central.ntua.gr

•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.

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