Faults & Fault Zones
Faults and Fault Zones
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 1
Faults & Fault Zones Faulting and Rock Mass Characterization: General Considerations
• The comprehension and recognition of the tectonic style and architecture of a region of geotechnical interest is of crucial importance for the development of a valid engineering geological model • Even isolated brittle shears are part of a fault system in close relationship with a regional stress regime (present or past) • Assessment of fault kinematics and sense of displacement reflects the tectonic regime with respect to stress axes orientations and relative sizes at the time of faulting • There are good reasons for the assumption that the kinematics of youngest brittle faults represent the present state of regional stress in a rock mass (see: fault plane solutions of earthquakes) • Present tectonic regime (extensional, wrench,...) and according local fault characteristics determine to a high degree some geotechnically important properties within a rock mass, as there are: permeability, stand-up time and stability performance, stress relief phenomena . . .
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 2
1 Faults & Fault Zones Characterization of Brittle Faults
- Faults are elongated complex zones of deformation, ranging from decimeters to kilometers in magnitude
- A significant internal structure of shear and extensional fractures has developed, reflecting the geometry of the strain field and, consequently, the orientation of the principal stresses
- The brittle deformation, such as particle size reduction by crushing of grains and reorientation of grains by shearing, generates the characteristic fine-grained gouge
- Low-temperature solution transfer contributes substantially to the alteration of fault rocks, in particular of gouge, through transformation and neo-formation of clay minerals
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 3
Faults & Fault Zones Terminology
• (Minor) Shear: Single fracture w/wo thin layer of crushed material (fault rock) between sheared - offset surfaces • Fault: General geological structure with shearing displacement of adjacent rock masses • Shear/Fault Zone: Elongate zone of displacement of considerable width, consisting of interlacing shear fractures or fault sets with or without fault rocks • Fault Rock: Product of host rock structural and/or mineralogical alteration due to brittle and/or ductile deformation during shearing; may be cohesive (coherent), incohesive or secondary indurated
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 4
2 Faults & Fault Zones Significance of Fault Zones
- The significant structural feature is a substantial heterogeneity, reflected by the occurrence of more or less undeformed competent blocks which are typically surrounded by a fine- grained matrix consisting of gouge and highly fractured rocks. The matrix appears to be flowing around the blocks in an anastomosing pattern
- The mainly lozenge shaped blocks exhibit a fractal distribution of dimensions, ranging from the microscale to hundreds of meters in length. Fault structures are scale independent
- A considerable heterogeneity of the stress field may exist. Variations in the stress field might be an important cause of segmentary fault zone formation
- Groundwater conditions are also highly variable. Water occurrence, pressures and flow directions may change dramatically across fault zones.
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 5
Faults & Fault Zones
Investigation of Faults
• Mapping of Morphological Features
• Detailed Outcrop Studies
- Characterization of Intact Rock - Characterization of Discontinuities - Paleostress Analysis
• Subsurface Investigation
- Trenches, Trial Pits - Core Drilling - Geophysical Survey
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 6
3 Faults & Fault Zones Detecting Faults... Geological Field Survey
Geological phenomena
• slickensides, striations: fault kinematics
• major joints
• severe fracturing
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 7
Faults & Fault Zones Detecting Faults... Geological Field Survey
Morphological phenomena
• Linear depressions associated with
- Seeps and / or
- Swamps
- Landslides
- Creeping areas
• Fault escarpment
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4 Faults & Fault Zones Indications of Faulting: Fault-Bound Rock Cliff (right) and Slickensided bedding, Sheared Beds in Outcrop
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Faults & Fault Zones Indications for faulting in covered regions: Trace of Fault Indicated by Surface Morphology, Mass Instability and Underground Water accumulation (Well)
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5 Faults & Fault Zones Rock mass instabilities are often associated with faults and fault rock material can be found frequently in particular at the base of sliding masses, both in natural and artificial outcrops
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 11
Faults & Fault Zones
Fault Scarp of Sub-Recent Activity (N- Anatolia)
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6 Faults & Fault Zones
Active Fault Escarpment, NE-Anatolian Fault Zone
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Faults & Fault Zones Activity: Offset of Paleosoils due to Neotectonic Fault Activity
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7 Faults & Fault Zones
Detecting faulting:
Large planar discontinuities or slickensided shear planes
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Faults & Fault Zones Detecting Faults:
Severe fracturing and development of curved shear planes (phacoids, below) as indication for faulting
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8 Faults & Fault Zones An estimate on potential fault activity and age is of utmost geotechnical importance in certain geotectonic settings. Activity assessment by: Seismic records, historical records, activity of associated mass movements (e. g. rock falls) Alterations of slickensided surfaces : Lustre, weathering, overgrowth, aperture, overprinting, Morphological features: Freshness of scarps – edges – steps - troughs, offset relations (ditches, fences, gutters, watercourses, soil or weathering horizons) development/age of vegetation, Mineralogical hints: Development of clay mineral assemblages, disturbed fill (overprinting/re-juvenation), crack-seal phenomena
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 17
Faults & Fault Zones
Age relationships established by overprinting relationships (displacement of features by shear along schistosity)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 18
9 Faults & Fault Zones Basic Principles of Tectonic Rock Deformation
• Brittle Shear Zone (Fault Zone): Contains fractures and cataclastic fault rocks, often accompanied by hydrothermal alterations • Ductile Shear Zone: Contains mylonites, i.e. structures that have a metamorphic aspect and that formed by ductile flow (crystal plasticity) • Brittle-Ductile Shear Zone: Show evidence of both brittle and ductile deformation, due to intermediate PT conditions or changing PT conditions during deformation.
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 19
Faults & Fault Zones Definitions of brittle deformation
• Brittle deformation is defined as strongly pressure dependent deformation involving an increase in volume as a result of cracking and it includes fracture and frictional sliding (Suppe, 1985).
• A macroscopic deformation process is defined as “brittle” if it is rate –independent and strain softening in the post-peak region (Mandl, 2000).
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 20
10 Faults & Fault Zones Earthquake activity is an expression of brittle deformation in the upper 10 km of the crust.
CHI-CHI - Earthquake, TAIWAN, 21. Sept. 1999, Magnitude 7.6, 2415 deaths with 8000 people injured
Legacy of Prof. Riedmüller Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 21
Faults & Fault Zones CHI-CHI - Earthquake, TAIWAN, 21. Sept. 1999
Klima, Schubert LegacyINSTITUTE of Prof. FOR Riedmüller ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 22
11 Faults & Fault Zones CHI-CHI - Earthquake, TAIWAN 21. Sept. 1999
Legacy of Prof. Riedmüller Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 23
Faults & Fault Zones The three basic fault types, their geometry and their relation to the driving stresses as described by Anderson (1942 & 1951):
normal fault thrust fault strike-slip fault
Mandl (2000)
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12 Faults & Fault Zones Basic fault types and kinematic axes
thrust fault normal fault
left lateral strike-slip faults right lateral
(sinistral) http://www.data.scec.org/glossary.html (dextral)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 25
Faults & Fault Zones Basic fault types and associated morphological features
taken from Ramsay & Huber (1987)
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13 Faults & Fault Zones
The brittle – ductile transition
• According to Sibson (1977), the transition from brittle deformation to plastic deformation takes place in a depth from 10 – 15 km at a temperature range from 250 to 350° C.
• This transition takes place where the influence of increasing temperature starts to prevail over the effect of increasing pressure (Suppe, 1985).
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 27
Faults & Fault Zones Conceptual model of a major fault zone and the associated fault rocks:
Incohesive gouge & breccia Strength trend as (pseudotachylite if dry) a function of depth
s1 –s3 1 - 4 km
Cohesive random- fabric crush breccias, rocks of the 10 - 15 km cataclasite series, Elastic-frictional pseudotachylite if dry regime
Brittle-ductile transition 250 – 350 °C
Cohesive foliated rocks Quasi-plastic regime of the mylonite series & blastomylonites ?
(after Sibson 1977, modified)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 28
14 Faults & Fault Zones Strutural units of a brittle fault zone
Billi et al. 2002
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Faults & Fault Zones
Strutural units of a brittle fault zone
Caine et al. 1996
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15 Faults & Fault Zones Fault Internal Structure: Core & Damage Zone
re t co faul
e zon age dam
k t roc hos
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Faults & Fault Zones Fault Internal Structure: Core & Damage Zone
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16 Faults & Fault Zones Tectonic Melange in an Alpine Thrust Setting
Foliated quartzite Blocks of dolomite marble
Graphitic Phyllite
Semmering Motorway, Tunnel Steinhaus, Austria Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 33
Faults & Fault Zones Tectonic Melange in an Alpine Thrust Setting Marble block with calcite filled extension fractures embedded in graphitic phyllite and foliated quartzite
Semmering Motorway, Tunnel Steinhaus, Austria Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 34
17 Faults & Fault Zones Tectonic Melange in an Alpine Thrust Setting
Blocks (phacoids) of quarzite embedded in graphite phyllite
Tunnel Steinhaus, Austria, Tunnel Face Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 35
Faults & Fault Zones Typical Structure of Ophiolitic Melange in Mesoscale Extension fractures Blocks of serpentinite
Extensional shears
4 cm base
Egnatia Motorway, N-Greece
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18 Faults & Fault Zones Typical Tectonic Melange
Egnatia Motorway, Northern Greece
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Faults & Fault Zones
Typical Tectonic Melange
Bolu Tunnel, Turkey
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19 Faults & Fault Zones Random Fabric of Marble Blocks (Mesoscale) Semmering-Base Tunnel, Austria
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 39
Faults & Fault Zones
Significantly Anisotropic Melange (Mesoscale) Diverse Elongate Blocks (Phacoids) in Foliated Matrix
5 cm
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 40
20 Faults & Fault Zones
Fault Zone Model, Blocks Show Fractal Dimensions, from the Micro – to the Megascale
FINE - GRAINED INTENSELY SHEARED LOZENGE - SHAPED BLOCKS OF NO GOUGE DEFORMATION
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Faults & Fault Zones Fault Zone in Gneiss („Zentralgneis“) HPP MALTA – Austrian Alps
Sample 1: Smectite 92% Illite 8%
Sample 1a: Smectite 87% Illite 13%
Sample 2a: Smectite 77% Mixed Layer 3% Kaolinite 17% Illite 3%
Sample 2b: Sample 40% Kaolinite 50% Illite 10%
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21 Faults & Fault Zones Systematic Transformations of Clay Minerals in Fault Zones (G. Riedmüller 1976)
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Faults & Fault Zones Brittle fault zones show frequently a pronounced contrast in their properties compared to the host rock.
Fault zone encountered in a highway NATM tunnel in Austria: Escape tunnel (right), main tunnel (below).
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22 Faults & Fault Zones The structures resulting from brittle deformation define the way water flows in hard rocks.
Without knowledge about the fracture systems incorporated in a rock mass flow of fluid can not be reliably determined.
http://geosurvey.state.co.us
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 45
Faults & Fault Zones Fault zones may act as aquiclude or aquifer Schematic fault zone models and fluid transport (ccz…Cataclasite zone, Process zone wake = damage zone)
Fault and host rock are Fault and host rock Fault is permeable along Inner conduit. Active permeable. Case where are impermeable. strike and in process fault, process zone protolith is clay free and zone and impermeable mineralized, cataclasite fault zone is transverse to strike. zone refractured. unmineralized. Transport only within cataclasite zone Scholz, C.H. & Anders, M.H.1994, http://www.ldeo.columbia.edu/~erict/Fault.html Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 46
23 Faults & Fault Zones Fault zones may act as aquiclude or aquifer
Fault Aquifer Aquiclude- Aquitarde
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Faults & Fault Zones Kinematic indicators related to brittle tectonics
• Offset of marker layers or beds • Conjugated shear fractures • Mineral fibres in steps (slickenfibres) • Secondary fractures (e.g. tensional fractures, Riedel shears) • Stylolithes (pressure solution seams) and slickolites (oblique stylolites) • Extension fractures (joints, en-echelon veins)
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24 Faults & Fault Zones
Offset of marker horizons
© Gerald Pischinger
Isoclinal fold is offset by normal fault
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Faults & Fault Zones Conjugated shear fractures
Θ In mechanically anisotropic rocks under brittle conditions, where all principal stresses are s 1 compressive, faults form at an inclination of Θ=±(45°-φ/2)
to the s1 axis. Where φ is the angle of internal friction.
s2
s3 © Gerald Pischinger s3 is perpendicular to picture plane! Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 50
25 Faults & Fault Zones
Kinematic indicators
Slickenside lineation Mineral fibres Slickolites
s s1 1 Shear plane Pull aparts
Stylolites Stylolitic seams
Dextral (top to right ) shear! (Meschede, 1994)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 51
Faults & Fault Zones Slickenfibres are very clear indicators!
Calcite slickenfibres with sinistral strike slip sense of shear (arrow shows sense of movement for missing block!).
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26 Faults & Fault Zones And which sense do we see here?
Oblique slip fault plane with calcite fibres and dextral sense of shear (arrow shows movement of missing block!).
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Faults & Fault Zones Multiple slickenlines and fibres
? ?
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27 Faults & Fault Zones Tectonic or diagenetic stresses may be accommodated by solution of rock (pressure solution →stylolite)
The peaks on the stylolite surfaces point into the direction of the maximum stress
direction s1.
Stylolites (pressure solution seams) are marked by a dark seam of insoluble material and show a highly serrated
profile. picture:http://www.gly.uga.edu/railsback/PDFindex1.html
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Faults & Fault Zones Oblique stylolites are termed “slickolites”
Slickolites are found on shear fractures and face against the movement direction of the missing block. Arrow indicates movement direction of missing block.
(taken from Ramsey & Huber, 1987)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 56
28 Faults & Fault Zones Slickolite striae are stylolites that run parallel to the discontinuity surface
Slickolite striae
Shear sense not ? deducible!
? Stylolite seams
(taken from Ramsey & Huber, 1987)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 57
Faults & Fault Zones
Stylolites and Slickolites
Slickolite surface profile Bedding plane s1
Normal stylolite profile
Calcite slickenfibres
s1 Slickolite surfaces Slickolite striae Bedding plane trace
(taken from Ramsey & Huber, 1987)
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29 Faults & Fault Zones Kinematic indicators – secondary fractures
Tensional fracture (“T”)
15° “Riedel”-shear (R1)
5° “Y” or master shear
10° “P”-shear
20° 40° 50° 70° 70°
Hybrid fractures “Riedel”-shear (R2) (after Logan et al. 1979 and Meschede 1994) Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 59
Faults & Fault Zones Secondary fracture pattern in experimental shear zone (quartz gouge).
Shear zone boundaries
R1 shears
R2 shears
(Logan et al. 1979) Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 60
30 Faults & Fault Zones Kinematic indicators – secondary fractures
Hanging wall half moon shaped break outs Fault plane Y P Foot wall
R2
R1
Slickenlines = Striations Tensile fracture (modified after Meschede, 1994)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 61
Faults & Fault Zones
Secondary fractures – Riedel criteria
RO (Riedel only)-criteria
Narrowly spaced R1 and R2 fractures (“Riedel”- shears) form saw tooth like profile in direction of slip, rarely found.
(after Petit (1987), taken from Meschede,1994)
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31 Faults & Fault Zones
Secondary fractures – Riedel criteria
R1Y-criteria
Fault plane (Y-shear) with pronounced
striation, breakouts along R1 Riedel shears, quite frequent type of feature.
(after Petit (1987), taken from Meschede,1994)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 63
Faults & Fault Zones Secondary fractures – Riedel criteria
R1Y-criteria
Fault plane (Y-shear) with pronounced striation, half-moon shaped breakouts (“lunate fractures”)
along R1 Riedel shears, frequent type of feature.
(after Petit (1987), taken from Meschede,1994)
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32 Faults & Fault Zones Secondary fractures – Riedel criteria
R1Y-criteria
Striation
Breakouts
along R1
(Petit, 1987) Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 65
Faults & Fault Zones
Secondary fractures – P criteria
PT-criteria
P T
Fault plane formed by striated P-shears with non-striated tensile fractures (“T”).
(after Petit (1987), taken from Meschede,1994)
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33 Faults & Fault Zones Secondary fractures – PT criteria
2 cm
PT structure on a left lateral strike-slip fault. Scale line is 2 cm. Arrow indicates sense of movement of the missing block (Petit, 1987).
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Faults & Fault Zones Secondary fractures – PT criteria
(Petit,1987)
PT structure with well developed T fractures, on a left-lateral strike-slip fault in the red Triassic High Atlas sandstone (Morocco). Stars are aligned along the trace of bedding plane on fault surface. Arrow indicates sense of movement of missing block
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34 Faults & Fault Zones Secondary fractures –Tensile fractures
“T”-criteria
Tensile fractures intersecting with striated fault plane
En-echelon, half-moon shaped tensile fractures (“crescentic fractures”)
(after Petit (1987), taken from Meschede,1994)
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Faults & Fault Zones Secondary fractures –Tensile fractures
“T”-criteria
En-echelon, half-moon shaped tensile fractures (“crescentic fractures”) in calcite- marble breccia.
En-echelon, half-moon shaped tensile fractures (“crescentic fractures”)
(sample courtesy of Prof. Brosch, TU Graz)
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35 Faults & Fault Zones Sigmoidal en-echelon veins - a result of continued shearing of extension fractures
taken from Meschede,1994 after Ramsey & Huber, 1983)
(taken from Ramsey & Huber, 1987)
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Faults & Fault Zones Joints occur frequently in a systematic pattern of nearly orthogonal sets
(http://piru.alexandria.ucsb.edu/collections/geography3b/p-s/ps-tab_06-10.jpg)
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36 Faults & Fault Zones Joint surfaces are sometimes characterized by plumose structures on their surfaces
(Ramsey & Huber, 1987) (http://www.globalchange.umich.edu/Ben/Pictures/Structure/structure.htm)
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Faults & Fault Zones Tectonics forms the earths surface over wide areas and therefore directly influences the living conditions of human beings.
Graz 90 m SRTM elevation model of the Eastern Alps – valleys follow mainly the fault zones formed in Miocene times during continental escape tectonics.
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37 Faults & Fault Zones Major Faults in Austria
alley Fault Innsbruck Salzach V M öll V Escape reaction alle y Fa ult Periadr iatic Fault Brenner - line Intender Venezia Katschberg - line
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Faults & Fault Zones
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38 Faults & Fault Zones Tectonic Activity and Stresses in Austria at Present
Selverstone 2005 Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 77
Faults & Fault Zones Geological Main Structures
Linzer, Decker, Peresson, Dell‘Mour & Frisch 2002 Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 78
39 Faults & Fault Zones
Important in Tunneling:
Differentiation of:
• Compressional Faults
- Strike-slip faults - Reverse faults - Thrust faults
• Extensional Faults
- Normal faults
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Faults & Fault Zones Normal-faulting stress-regime
low horizontal stresses, often loosening of mass, open steep fractures, high conductivity, De-stressed, for large parts desintegrated Rock Mass Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 80
40 Faults & Fault Zones
Fault?
Highly fractured corridor (fracture zone in extensional regime) without noticeable displacement, geotechnically to be considered as zone of weakness of highest importance
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Faults & Fault Zones The geotechnical significance of faulting in an extensional regime lies in the stress relief and potential high conductivity
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41 Faults & Fault Zones Reverse-faulting stress-regime
High horizontal stresses, low-angle faults, tight faults of low permeability, thick fine-grained gouges (tectonic melanges), high seismic hazards
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Faults & Fault Zones
Thrust faults with phacoidal shearing, extension of competent beds, interlacing structure
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42 Faults & Fault Zones
Foliated soft matrix showing Lenticular stiff block showing ductile and brittle compressional extension fractures deformation features
Quartzitic Sandstone, Devonian
Graphitic Shale, Carboniferous
Formation of Melange in an Foreland Basin Overthrust Setting, Main Tunnel, Mae Kuang Irrigation Project, N – Thailand Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 85
Faults & Fault Zones
Characterisation of • Block / Matrix Ratio Faulted Rock Mass: Key Parameters • Matrix Properties • Particle Size Distribution • Clay Mineral Composition • Swelling Properties • Shear Strength
• Block Properties • Lithology •Size • Shape • Strength
• Discontinuities • Type (shear, extension fractures etc.) • Orientation • Fracture Degree • Relative Movements on Slickensides
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43 Faults & Fault Zones Engineering Geological Classification of Fault Rocks (Riedmüller et al., Felsbau 19 (2001) No. 4)
> 75% Blocky Rock Mass
Volumetric Block Blocks 1 25 - 75% Tectonic Bimrock Proportion
Cohesi Strength < 25% Heavily on-less Ratio: Fractured (Soil-like Block/ G-Cataclasite 3 Rock Mass material) Matrix Coarse- grained >0,063mm 2 S-Cataclasite 3 Cataclastic Particle Size Matrix Rocks < 63 mm Fine- M-Cataclasite 3 Mylonitic grained Rocks <0,063mm 4 C-Cataclasite 3
Ferritic
Cohesive Cementation Type of Cement Carbonatic Fault Breccia
1 Block size depends on scale of engineering interest Siliceous 2 Subsequent differentiation is based on grain size and grading
3 Further differentiation according to USCS standard procedure Pseudo- Glassy 4 Differentiation is based on plasticity index and liquid limit (A-line) tachylyte
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 87
Faults & Fault Zones Fault rocks of very limited geotechnical significance: Mylonite (below) and indurated breccias (left)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 88
44 Faults & Fault Zones „Kakirite“ (incohesive, not layered) or G – S Cataclasite with single blocks
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 89
Faults & Fault Zones
Different fault rock development in normal (above), Breccia – G- Cataclasite) and thrust fault regimes (S-G Cataclasite)
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 90
45 Faults & Fault Zones Clayey Fault Gouge, M-C Cataclasite Even very thin gouges along shears (difficult to detect!) may reduce rock mass quality considerably and may lead to unexpected behavior and failure!
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 91
Faults & Fault Zones Clayey Fault Gouge with a few Large Fragments, m-Scale C-M-S Cataclasite,
Small amounts of large intraclasts (blocks) do not affect matrix- dependent strength and shear behavior
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46 Faults & Fault Zones Example Fault Rock Characterization Sheet as a Rock Mass Type (RMT) according to Austrian Practice
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 93
Faults & Fault Zones Fault Rocks: Recommended Investigations (depending on design phase and project requirements)
- Assessment of block – matrix ratio (depending on scale of interest) - Strength (soil – rock mechanic tests, in particular for shear strength and its variability) - Grain size distribution - Bulk composition (lithology / mineralogy of both components and matrix, semiquantitative) - Quantitative mineralogy of the grain size fraction <0.002 mm - Determination of swelling potential in clay minerals fraction - General behavior with water access (hydrological function)
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47 Faults & Fault Zones
Crossing the “Lavanttal” fault system, Koralmtunnel, Austria
• Regional fault system
• Oblique strike slip character
• About 4 km of displacement
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 95
Faults & Fault Zones Koralm Tunnel: Geological Overview
Wolfsberg Deutschlandsberg
Großer Speikkogel
St. Paul im Lavanttal
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48 Faults & Fault Zones Koralm Tunnel: Geological Section
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 97
Faults & Fault Zones Koralpe overview longitudinal section
ENE STEIERMARK KÄRNTEN WSW
Erkundungsstollen Schacht LAVANTTAL Zwischenangriff LEIBENFELD Erkundungsstollen Erkundungsstollen Portal LAVANTTAL LEIBENFELD Schacht LAVANTTAL
GRAZ KLAGENFURT NÖT TBM TBM TBM / NÖT TBM / NÖT
LEGEND: 32,8 km
Tertiäre Lockergesteine Kristallingesteine (Gneis-Glimmerschiefer, Quarzreicher Feinkorngneis, Plattengneis)
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49 Faults & Fault Zones
Preliminary Design Geological Architecture
Koralm Tunnel, Austria
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Faults & Fault Zones Koralpe West - Lavanttal fault system
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50 Faults & Fault Zones Koralpe West - Lavanttal fault system
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Faults & Fault Zones
Koralm Tunnel
Hydraulic Fault Zone Definitions (modified after Caine et al. 1996) Typ I, Major Strike-Slip Fault in Crystalline Basement Well-developed Fault Core (predominantly M- and C- cataclasites) with low permeability) surrounded by high permeable Fracture Zone (G- and S-cataclasite) and Blocky Rock Mass Typ II Major Strike-Slip Fault in Tertiary Clastic Sediments Fault Core poorly developed. No Fracture Zones Typ III Normal Fault in Crystalline Basement Fault Core poorly developed. Well-developed Fracture Zone associated with high permeable fracture network
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51 Faults & Fault Zones Koralm Tunnel
Hydraulic Model, Finite element model (FRACTure) maximum possible lowering of the Simulation of hydraulic, elastic, and groundwater table transport processes 54 hydro-geological units 437.000 nodes
• Conservative Model (1D Hydraulic Flow)
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Faults & Fault Zones „Lavanttaler“ Fault system, geological documentation ENE WSW Drive direction Longitudinal section
Horizontal section
68+700 68+800 68+900 69+000 69+100 Shistosity Joints Faults / slikensides
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52 Faults & Fault Zones Fault types
Fault type 2 Fault type 1
Fault type 4 Fault type 3
samples
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Faults & Fault Zones Fault type 1
Sketch of tunnel face
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53 Faults & Fault Zones Fault type 1
Tunnel Paierdorf Area: 6.5 m2 Chainage 960 ‐ 1006 m Matrix: 3.4 m2 52% Ratio blocks / matrix Blocks: 3.1 m2 48%
Area: 7.0 m2 Matrix: 4.6 m2 66% Blocks: 2.4 m2 34%
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Faults & Fault Zones Fault type 1
Tectonic Bimrock - competent crystalline blocks in fine- to coarse grained matrix - blocks tectonically stressed, moderate strength (25-50 MPa) - some slickensides, undulated / polished, with clayey coating
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54 Faults & Fault Zones Fault type 2
Störungstyp 02 Kristallin
Sketch of tunnel face
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Faults & Fault Zones Fault type 2 - Coarse grained fault gouge Area: 4.2 m2 Tunnel Paierdorf Matrix: 2.8 m2 67% Chainage 1030 ‐1145 m Blocks: 1.4 m2 33% Ratio blocks / matrix
Grain size distribution of the matrix
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55 Faults & Fault Zones Fault type 3
Sketch of tunnel face
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Faults & Fault Zones Fault type 3
Tunnel Paierdorf Chainage 1168 – 1285 m Ratio blocks / matrix Area: 76.3 cm2 Matrix: 60.8 cm2 80% Blocks: 15.5 cm2 20%
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56 Faults & Fault Zones Fault type 3 Volumetric fraction: B M Stat. VO 1187,5 m Fine grained fault gouge 2D-analysis: 20% / 80% Mass fraction: 30% / 70% density block: 2,8 g/cm³ density matrix: 2,2 g/cm³
Conversion Mass - Volume: 25% / 75% correction 2D- to 3D-analysis: 5%
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Faults & Fault Zones Fault type 3 – fine grained gouge
Tunnel Paierdorf, fine grained fault gouge, Chainage 1187.5 m
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57 Faults & Fault Zones Fault type 3
Stack out of tectonically stressed crystalline rock blocks and fault gouge - remarkable contrast in stiffness - varying intact rock and rock mass strength due to tectonical stress and resulting decomposition - Highly anisotropic
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Faults & Fault Zones Fault type 4
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58 Faults & Fault Zones Fault type 4
• Fault gouge with thin shears
• Highly anisotropic
Tunnel Paierdorf Chainage 1302.6 m
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Faults & Fault Zones Fault type 4
Fault gouge (clay to sand) containing shear lenses of size of gravel to cobbles - (very) low strength - plastic behavior, partly over consolidated (tectonic stress) - intensively folded in small scale - sheared (predominantly parallel to foliation) - dominant slickensides, undulated / polished
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 118
59 Faults & Fault Zones Particle size distribution from fault gouge samples chainage 938-1350 m Drive direction
Particle Size Distribution
60
GravelKies 50 Sand 40 SchluffSilt Mass % Mass ClayTon 30 LinearGravel (Kies) LinearSand (Sand) Massenprozent 20 LinearSilt (Schluff) 10 LinearClay (Ton)
0 1234567 SampleProben
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Faults & Fault Zones
Tunnel failure due to extensional faulting Tunel Buenavista, Colombia 2000
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60 Faults & Fault Zones Tectonic model of Colombia 1994
A. Lobo-Guerrero Uscategui 1994
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Faults & Fault Zones
Tectonic section 1994
Tectonic model of Colombia 1994 A. Lobo-Guerrero Uscategui 1994 Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 122
61 Faults & Fault Zones
Guaicáramo fault system INGEOMINAS 1983 Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 123
Faults & Fault Zones Fault pattern
Fault pattern as predicted Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 124
62 Faults & Fault Zones Longitudinal section
Ingetec 1993 Geology: Túnel Buenavista • Formación Terciario sin diferenciar (Tsd) rhythmic stratification of sandstone and claystone Length of tunnel: 4519.5 m • Formación Cáqueza inferior (Kic) Max. overburden: 600 m black shale (oil and gas bearing) Area of section: 75 m2 • Formación Brechas de Buenavista (Jbb) Total costs: ~77 Mio $ breccia and conglomerate Elevation: ~ 700 m • Grupo Quetame (εoq) quartzite, quartz conglomerate, phyllit
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 125
Faults & Fault Zones
•Client: Republica de Colombia, Ministerio de Transporte Instituto Nacional de Vias
•Contractor 1995 - 1997: Recchi Spa – Grandi Lavori Fincosit Spa, Italia (excavated 1078,85 m)
•Interventoria 1995 – 1997: Consultoría Colombiana – Coyne et Bellier
•Contractor 1998 – 2002: Conconcreto S.A., Colombia (excavated 3440,65 m)
•Interventoria 1998 – 2002: UNION TEMPORAL – D.I.S.- E.D.L.- D2 Consult
Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011
S p e c 126 s
63 Faults & Fault Zones Longitudinal section Frente Trapiche
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Faults & Fault Zones
Frente Trapiche
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64 Faults & Fault Zones
Frente Trapiche grouted rock mass Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 129
Faults & Fault Zones
Thrust fault
Strike slip fault
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65 Faults & Fault Zones
Fault gouge
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Faults & Fault Zones
Fault gouge Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 132
66 Faults & Fault Zones
Falla de Servitá
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Faults & Fault Zones
Falla de Servitá
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67 Faults & Fault Zones Falla del Mirador Rio Guatiquia
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Faults & Fault Zones
Established tectonic models
Thrust faults
basement faults
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68 Faults & Fault Zones
Final LS
joints Mirador shear II Servita Guaicaramo
Buenavista joints shear III Trapiche
joints
bedding shear I bedding Buque tunnel joints
shear IV tunnel
shear V
All discontinuities Strike of mayor faults
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Faults & Fault Zones Finally proposed tectonic model
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69 Faults & Fault Zones
Consequences Klima, Schubert INSTITUTE FOR ROCK MECHANICS AND TUNNELING Short Course Singapore 2011 139
Faults & Fault Zones Support class distribution predicted vs real
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70