Geotechnical properties of rocks
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About This Presentation
Engineering geology is the application of the science of geology to the technology of ground engineering. The subject requires a comprehensive knowledge of geology, as well as an understanding of engineering properties and behaviour of the geological materials. The practice involves site investigati...
Slide Content
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GEOTECHNICAL PROPERTIES OF ROCKS
By Prof A. Balasubramanian
Centre for Advanced Studies in Earth Science
University of Mysore
Mysore-6
GEOTECHNICAL PROPERTIES OF ROCKS
By Prof A. Balasubramanian
Centre for Advanced Studies in Earth Science
University of Mysore
Mysore-6
2
Introduction:
Engineering geology is the application of the
science of geology to the technology of ground
engineering.
The subject requires a comprehensive
knowledge of geology, as well as an
understanding of engineering properties and
behaviour of the geological materials.
Introduction:
Engineering geology is the application of the
science of geology to the technology of ground
engineering.
The subject requires a comprehensive
knowledge of geology, as well as an
understanding of engineering properties and
behaviour of the geological materials.
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The practice involves site investigation and site
characterization specific to the needs of the
engineering project.
The geotechnical engineer plays a key role in
most civil engineering projects as most
structures are built on or in the ground.
Geotechnical engineers assess the properties
and behaviour of soil and rock formations.
The practice involves site investigation and site
characterization specific to the needs of the
engineering project.
The geotechnical engineer plays a key role in
most civil engineering projects as most
structures are built on or in the ground.
Geotechnical engineers assess the properties
and behaviour of soil and rock formations.
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1. Geotechnical engineering:
It is a collective term for the more individual
disciplines of:
Soil mechanics ,
Foundation engineering ,
Engineering geology and hydrology ,
Environmental science ,
Rock mechanics ,
Rock engineering ;and Other related disciplines
to civil engineering design and construction.
1. Geotechnical engineering:
It is a collective term for the more individual
disciplines of:
Soil mechanics ,
Foundation engineering ,
Engineering geology and hydrology ,
Environmental science ,
Rock mechanics ,
Rock engineering ;and Other related disciplines
to civil engineering design and construction.
5
The geotechnical engineer may, for example,
assess the materials to be used for the stability
of dams, roads, channels, bridges, highways, UG
pipelines, tunnels and airport runways.
Investigations:
Site evaluation for geomorphology, geology,
structure, strong and weak zones, seismicity.
Materials evaluation for their suitability (for
foundation, stability of structure,construction.
The geotechnical engineer may, for example,
assess the materials to be used for the stability
of dams, roads, channels, bridges, highways, UG
pipelines, tunnels and airport runways.
Investigations:
Site evaluation for geomorphology, geology,
structure, strong and weak zones, seismicity.
Materials evaluation for their suitability (for
foundation, stability of structure,construction.
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2. Methods of determining rock properties :
Subsurface soil or rock properties are generally
determined using one or more of the following
methods:
• in-situ testing during the field exploration
program,
• laboratory testing, and
• back analysis based on site performance data.
2. Methods of determining rock properties :
Subsurface soil or rock properties are generally
determined using one or more of the following
methods:
• in-situ testing during the field exploration
program,
• laboratory testing, and
• back analysis based on site performance data.
7
In-situ testing to evaluate rock mass
deformation modulus and shear strength is
sometimes required for the design of
foundations for major structures such as dams
and bridges, however, such testing is not
performed for structural foundations or slopes
associated with typical highway applications.
In-situ testing to evaluate rock mass
deformation modulus and shear strength is
sometimes required for the design of
foundations for major structures such as dams
and bridges, however, such testing is not
performed for structural foundations or slopes
associated with typical highway applications.
8
A laboratory-testing program consists of index
tests to obtain general information on material
consistency and performance tests to measure
specific properties (e.g., shear strength,
compressibility, hydraulic conductivity) for
design and constructability assessments.
A laboratory-testing program consists of index
tests to obtain general information on material
consistency and performance tests to measure
specific properties (e.g., shear strength,
compressibility, hydraulic conductivity) for
design and constructability assessments.
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3. TWO different Properties of Rocks:
The properties of rock fall into two broad
classes: a) rock material properties relating to
the rock itself and b) rock mass properties
relating to the in-place rock mass, including its
discontinuities.
3. TWO different Properties of Rocks:
The properties of rock fall into two broad
classes: a) rock material properties relating to
the rock itself and b) rock mass properties
relating to the in-place rock mass, including its
discontinuities.
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4. Rock material properties that are essential
in assessing hydraulic erodibility of rock include
rock type, color, particle size, texture, hardness,
and strength.
Seismic velocity, weathering, and secondary
cavities are properties related to both the rock
material and mass.
4. Rock material properties that are essential
in assessing hydraulic erodibility of rock include
rock type, color, particle size, texture, hardness,
and strength.
Seismic velocity, weathering, and secondary
cavities are properties related to both the rock
material and mass.
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5. Rock mass properties are comprised of
features generally observed, measured, and
documented in the field for in-place rock.
The properties of a rock mass are significantly
different from the properties of samples of the
same rock mass.
5. Rock mass properties are comprised of
features generally observed, measured, and
documented in the field for in-place rock.
The properties of a rock mass are significantly
different from the properties of samples of the
same rock mass.
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The strength and mechanical behavior of the
rock mass are commonly dominated more by
the nature of its mass properties than by its
material properties.
6. ROCK (sample) MATERIAL PROPERTIES:
Rock material properties are measurable or
describable lithologic properties of rock material
that can be evaluated in hand specimens or
tested in the laboratory.
The strength and mechanical behavior of the
rock mass are commonly dominated more by
the nature of its mass properties than by its
material properties.
6. ROCK (sample) MATERIAL PROPERTIES:
Rock material properties are measurable or
describable lithologic properties of rock material
that can be evaluated in hand specimens or
tested in the laboratory.
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Rock material properties are related to the
physical properties of the rock-forming minerals
and the type of mineral bonding.
Properties are determined from hand
specimens, core sections, drill cuttings,
outcroppings, and disturbed samples using
qualitative procedures, simple classification
tests, or laboratory tests.
Rock material properties are related to the
physical properties of the rock-forming minerals
and the type of mineral bonding.
Properties are determined from hand
specimens, core sections, drill cuttings,
outcroppings, and disturbed samples using
qualitative procedures, simple classification
tests, or laboratory tests.
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7. Punch-Penetration Index Test:
The punch-penetration index test evaluates the
penetration resistance of the intact rock cores.
Because the punch-penetration test actually
penetrates the rock, it provides the capability to
reveal some important rock excavatability
features that other tests may fail to illustrate.
7. Punch-Penetration Index Test:
The punch-penetration index test evaluates the
penetration resistance of the intact rock cores.
Because the punch-penetration test actually
penetrates the rock, it provides the capability to
reveal some important rock excavatability
features that other tests may fail to illustrate.
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One important feature which the punch-
penetration test has been successful in
identifying is rock toughness.
8. Thin Section Petrographic Analysis :
Thin section petrographic analysis is used to
evaluate the mineralogy of the intact rock cores.
In petrography, the mineral content and the
textural relationships within the rock are
described in detail.
One important feature which the punch-
penetration test has been successful in
identifying is rock toughness.
8. Thin Section Petrographic Analysis :
Thin section petrographic analysis is used to
evaluate the mineralogy of the intact rock cores.
In petrography, the mineral content and the
textural relationships within the rock are
described in detail.
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9. Elasticity:
The elasticity is the property of a substance to
deform with external forces and return to its
original shape when the stress is removed.
The deformation fully capable of restoration is
called elastic deformation.
9. Elasticity:
The elasticity is the property of a substance to
deform with external forces and return to its
original shape when the stress is removed.
The deformation fully capable of restoration is
called elastic deformation.
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Within the range of the
elastic deformation,
the ratio of the stress ( 0)to
the strain ( E ) is a constant (E) which is known as
elastic modulus, namely, E= O/ E.
The elastic modulus is a measure of the ability to
resist deformation.
Within the range of the
elastic deformation,
the ratio of the stress ( 0)to
the strain ( E ) is a constant (E) which is known as
elastic modulus, namely, E= O/ E.
The elastic modulus is a measure of the ability to
resist deformation.
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10. Plasticity:
The plasticity describes the deformation of a
material undergoing non-reversible changes of
shape in response to external forces.
This non-reversible deformation is called plastic
deformation.
10. Plasticity:
The plasticity describes the deformation of a
material undergoing non-reversible changes of
shape in response to external forces.
This non-reversible deformation is called plastic
deformation.
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11. Brittleness and Toughness:
Brittleness: Brittleness describes the property of
a material that fractures when subjected to
stress but has a little tendency to deform before
rupture.
Brittle materials are characterized by little
deformation, poor capacity to resist impact and
vibration of load, high compressive strength, and
low tensile strength.
11. Brittleness and Toughness:
Brittleness: Brittleness describes the property of
a material that fractures when subjected to
stress but has a little tendency to deform before
rupture.
Brittle materials are characterized by little
deformation, poor capacity to resist impact and
vibration of load, high compressive strength, and
low tensile strength.
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Most of inorganic non-metallic materials are
brittle materials.
Toughness:
Impacted or vibrated by stress, a material is able
to absorb much energy and deform greatly
without rupture, which is known as toughness,
also called impact toughness.
Tough materials are characterized by great
deformation,
Most of inorganic non-metallic materials are
brittle materials.
Toughness:
Impacted or vibrated by stress, a material is able
to absorb much energy and deform greatly
without rupture, which is known as toughness,
also called impact toughness.
Tough materials are characterized by great
deformation,
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high tensile strength, and high compressive
strength, such as construction steel, wood and
rubber.
12. Hardness:
Hardness refers to the property of a material to
resist pressing-in or scratch of a sharp object.
The materials of different kinds of hardness
need various testing methods.
The hardness of steel, wood and concrete is
tested by pressing-in method.
high tensile strength, and high compressive
strength, such as construction steel, wood and
rubber.
12. Hardness:
Hardness refers to the property of a material to
resist pressing-in or scratch of a sharp object.
The materials of different kinds of hardness
need various testing methods.
The hardness of steel, wood and concrete is
tested by pressing-in method.
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Hardness is the subjective description of the
resistance of an earth material to permanent
deformation, particularly by indentation
(impact) or abrasion (scratching).
Rock hardness is not the same as mineral
hardness.
The Moh's scale is a qualitative scale for a set of
empirical tests used to differentiate minerals in
hand specimens by scratching.
Hardness is the subjective description of the
resistance of an earth material to permanent
deformation, particularly by indentation
(impact) or abrasion (scratching).
Rock hardness is not the same as mineral
hardness.
The Moh's scale is a qualitative scale for a set of
empirical tests used to differentiate minerals in
hand specimens by scratching.
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The scale has no useful application in describing
most rock material for engineering purposes
because most rock types are aggregates of more
than one mineral.
Hardness is simply a qualitative expression of
earth material strength; the hardness categories
form a scale of ranges in strength values
obtained from the laboratory test for strength.
The scale has no useful application in describing
most rock material for engineering purposes
because most rock types are aggregates of more
than one mineral.
Hardness is simply a qualitative expression of
earth material strength; the hardness categories
form a scale of ranges in strength values
obtained from the laboratory test for strength.
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Hardness category =Very soft rock or hard, soil
like material , Moderately soft rock, Moderately
hard rock, Hard rock , Very hard rock, Extremely
hard rock.
A scale of rock hardness :
1. Soft. All rocks weaker than 5 on the scale-of-
strength.
2. Moderately hard. Slightly friable or nonfriable
rocks consisting mainly of soft minerals, as
carbonates, sulfates, micas, and clays.
Hardness category =Very soft rock or hard, soil
like material , Moderately soft rock, Moderately
hard rock, Hard rock , Very hard rock, Extremely
hard rock.
A scale of rock hardness :
1. Soft. All rocks weaker than 5 on the scale-of-
strength.
2. Moderately hard. Slightly friable or nonfriable
rocks consisting mainly of soft minerals, as
carbonates, sulfates, micas, and clays.
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3. Hard. Nonfriable rocks consisting almost
entirely of minerals with hardnesses of 4, 5, or 6
on the Mohs scale, and quartz-rich rocks with
strength of 6 or 7.
4. Very hard. Rocks stronger than 7 on the scale
above and consisting mainly of minerals harder
than 6 on the Mohs scale.
3. Hard. Nonfriable rocks consisting almost
entirely of minerals with hardnesses of 4, 5, or 6
on the Mohs scale, and quartz-rich rocks with
strength of 6 or 7.
4. Very hard. Rocks stronger than 7 on the scale
above and consisting mainly of minerals harder
than 6 on the Mohs scale.
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13. ROCK(body) MASS PROPERTIES:
Typical elements include:
• principal rock type,
• mineralogy (estimate percentage of principal
and accessory minerals; note type of cement
and presence of alterable minerals),
• primary porosity (free draining or not).
• hardness and unconfined compressive
strength categories unit weight (dry),
13. ROCK(body) MASS PROPERTIES:
Typical elements include:
• principal rock type,
• mineralogy (estimate percentage of principal
and accessory minerals; note type of cement
and presence of alterable minerals),
• primary porosity (free draining or not).
• hardness and unconfined compressive
strength categories unit weight (dry),
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• unit weight (dry),
• color,
• discrete rock particle size.
Essential aspects include geologic descriptions,
engineering classification, shear strength
parameters, bearing capacity parameters, and
deformation and settlement parameters.
• unit weight (dry),
• color,
• discrete rock particle size.
Essential aspects include geologic descriptions,
engineering classification, shear strength
parameters, bearing capacity parameters, and
deformation and settlement parameters.
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14. Rock type:
Rock type is a simplified geologic classification of
rock based on its genetic category, structure,
composition, and grain size.
Rock type can indicate mineralogical and
textural characteristics, which may provide
insight into the physical and chemical interaction
between the grains.
14. Rock type:
Rock type is a simplified geologic classification of
rock based on its genetic category, structure,
composition, and grain size.
Rock type can indicate mineralogical and
textural characteristics, which may provide
insight into the physical and chemical interaction
between the grains.
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Using standard field identification procedures
all identified rock units and record the rock
types, are to be classified.
The properties of rocks include Rock texture
(particle size), Rock stability(strength),
Permeability of the rock, Mineralogical
composition of the rock and Rock resistance to
weathering.
Using standard field identification procedures
all identified rock units and record the rock
types, are to be classified.
The properties of rocks include Rock texture
(particle size), Rock stability(strength),
Permeability of the rock, Mineralogical
composition of the rock and Rock resistance to
weathering.
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15. Intact Rock versus Rock Mass :
The in-situ rock, or rock mass, is comprised of
intact blocks of rock separated by discontinuities
such as joints,
bedding planes, folds, sheared zones and faults.
These rock blocks may vary from fresh and
unaltered rock to badly decomposed and
disintegrated rock.
15. Intact Rock versus Rock Mass :
The in-situ rock, or rock mass, is comprised of
intact blocks of rock separated by discontinuities
such as joints,
bedding planes, folds, sheared zones and faults.
These rock blocks may vary from fresh and
unaltered rock to badly decomposed and
disintegrated rock.
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Under applied stress, the rock mass behavior is
generally governed by the interaction of the
intact rock blocks with the discontinuities.
Under applied stress, the rock mass behavior is
generally governed by the interaction of the
intact rock blocks with the discontinuities.
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16. Degree of Weathering:
(1) Unweathered: No evidence of any chemical
or mechanical alteration.
(2) Slightly weathered: Slight discoloration on
surface, slight alteration along discontinuities,
less than 10 percent of the rock. volume
altered.
(3) Moderately weathered: Discoloring evident,
surface pitted and altered with alteration
penetrating well below rock surfaces,
16. Degree of Weathering:
(1) Unweathered: No evidence of any chemical
or mechanical alteration.
(2) Slightly weathered: Slight discoloration on
surface, slight alteration along discontinuities,
less than 10 percent of the rock. volume
altered.
(3) Moderately weathered: Discoloring evident,
surface pitted and altered with alteration
penetrating well below rock surfaces,
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weathering “halos” evident, 10 to 50 percent of
the rock altered.
(4) Highly weathered: Entire mass discolored,
alteracation pervading nearly all of the rock with
some pockets of slightly weathered rock
noticeable, some minerals leached away.
(5) Decomposed: Rock reduced to a soil with
relicit rock texture, generally molded and
crumbled by hand.
weathering “halos” evident, 10 to 50 percent of
the rock altered.
(4) Highly weathered: Entire mass discolored,
alteracation pervading nearly all of the rock with
some pockets of slightly weathered rock
noticeable, some minerals leached away.
(5) Decomposed: Rock reduced to a soil with
relicit rock texture, generally molded and
crumbled by hand.
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17. Texture of rocks.
18. Lithology, Macro Description of Mineral
Components. Use standard adjectives such as
shaly, sandy, silty, and calcareous. Note
inclusions, concretions, nodules, etc.
19. Rock Structures.
17. Texture of rocks.
18. Lithology, Macro Description of Mineral
Components. Use standard adjectives such as
shaly, sandy, silty, and calcareous. Note
inclusions, concretions, nodules, etc.
19. Rock Structures.
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20. Thickness of Bedding:
(1) Massive: 3-ft thick or greater.
(2) Thick bedded: beds from 1- to 3-ft thick.
(3) Medium bedded: beds from 4 in. to 1-ft thick.
(4) Thin bedded: 4-in. thick or less.
20. Thickness of Bedding:
(1) Massive: 3-ft thick or greater.
(2) Thick bedded: beds from 1- to 3-ft thick.
(3) Medium bedded: beds from 4 in. to 1-ft thick.
(4) Thin bedded: 4-in. thick or less.
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21. Degree of Fracturing (Jointing):
(1) Unfractured: fracture spacing - 6 ft or more.
(2) Slightly fractured: fracture spacing - 2 to 6 ft.
(3) Moderately fractured: fracture spacing - 8 in.
to 2 ft.
(4) Highly fractured: fracture spacing - 2 in. to 8
in.
(5) Intensely fractured: fracture spacing - 2 in. or
less.
21. Degree of Fracturing (Jointing):
(1) Unfractured: fracture spacing - 6 ft or more.
(2) Slightly fractured: fracture spacing - 2 to 6 ft.
(3) Moderately fractured: fracture spacing - 8 in.
to 2 ft.
(4) Highly fractured: fracture spacing - 2 in. to 8
in.
(5) Intensely fractured: fracture spacing - 2 in. or
less.
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Dip of Bed or Fracture:
(1) Flat: 0 to 20 degrees.
(2) Dipping: 20 to 45 degrees.
(3) Steeply dipping: 45 to 90 degrees.
22. Discontinuities:
a. Joints:
(1) Type: Type of joint if it can be readily
determined (i.e., bedding, cleavage, foliation,
schistosity, or extension).
Dip of Bed or Fracture:
(1) Flat: 0 to 20 degrees.
(2) Dipping: 20 to 45 degrees.
(3) Steeply dipping: 45 to 90 degrees.
22. Discontinuities:
a. Joints:
(1) Type: Type of joint if it can be readily
determined (i.e., bedding, cleavage, foliation,
schistosity, or extension).
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(2) Degree of joint wall weathering:
(i) Unweathered: No visible signs are noted of
weathering; joint wall rock is fresh, crystal
bright.
(ii) Slightly weathered joints: Discontinuities are
stained or discolored and may contain a thin
coating of altered material.
(2) Degree of joint wall weathering:
(i) Unweathered: No visible signs are noted of
weathering; joint wall rock is fresh, crystal
bright.
(ii) Slightly weathered joints: Discontinuities are
stained or discolored and may contain a thin
coating of altered material.
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Discoloration may extend into the rock from the
discontinuity surfaces to a distance of up to 20
percent of the discontinuity spacing.
(iii) Moderately weathered joints: Slight
discoloration extends from discontinuity planes
for greater than 20 percent of the discontinuity
spacing. Discontinuities may contain filling of
altered material. Partial opening of grain
boundaries may be observed.
Discoloration may extend into the rock from the
discontinuity surfaces to a distance of up to 20
percent of the discontinuity spacing.
(iii) Moderately weathered joints: Slight
discoloration extends from discontinuity planes
for greater than 20 percent of the discontinuity
spacing. Discontinuities may contain filling of
altered material. Partial opening of grain
boundaries may be observed.
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(iv) Highly weathered joints: same as Item
1.a.(4). (v) Completely weathered joints:
23. Faults and Shear Zones:
(1) Extent: Single plane or zone; how thick.
(2) Character: Crushed rock, gouge, clay infilling,
slickensides.
(iv) Highly weathered joints: same as Item
1.a.(4). (v) Completely weathered joints:
23. Faults and Shear Zones:
(1) Extent: Single plane or zone; how thick.
(2) Character: Crushed rock, gouge, clay infilling,
slickensides.
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24. Shear Strength: The shear strength that
can be developed to resist sliding in a rock
foundation or a rock slope is generally controlled
by natural planes of discontinuity rather than
the intact rock strength.
Rock Failure Characteristics: Failure of a
foundation or slope can occur through the
intact rock, along discontinuities or through
filling material contained between
discontinuities.
24. Shear Strength: The shear strength that
can be developed to resist sliding in a rock
foundation or a rock slope is generally controlled
by natural planes of discontinuity rather than
the intact rock strength.
Rock Failure Characteristics: Failure of a
foundation or slope can occur through the
intact rock, along discontinuities or through
filling material contained between
discontinuities.
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Failure Criteria: a. Definition of failure. The term
“failure” as applied to shear strength may be
described in terms of load, stress, deformation,
strain or other parameters.
Laboratory direct shear: Strength along planes of
weakness (bedding), discontinuities or rock-
concrete contact; not recommended for intact
rock.
Failure Criteria: a. Definition of failure. The term
“failure” as applied to shear strength may be
described in terms of load, stress, deformation,
strain or other parameters.
Laboratory direct shear: Strength along planes of
weakness (bedding), discontinuities or rock-
concrete contact; not recommended for intact
rock.
43
25. Deformation and Settlement:
The deformational response of a rock mass is
important in seismic analyses of dams and other
large structures as well as the static design of
gravity and arch dams, tunnels, and certain
military projects.
25. Deformation and Settlement:
The deformational response of a rock mass is
important in seismic analyses of dams and other
large structures as well as the static design of
gravity and arch dams, tunnels, and certain
military projects.
44
26. Moduli Definitions:
The elastic modulus relates the change in
applied stress to the change in the resulting
strain.
Mathematically, it is expressed as the slope of a
given stress-strain response. ex. Elastic modulus.
26. Moduli Definitions:
The elastic modulus relates the change in
applied stress to the change in the resulting
strain.
Mathematically, it is expressed as the slope of a
given stress-strain response. ex. Elastic modulus.
45
Categories of Rock Mass Deformation:
Deformations that may lead to settlement or
heave of structures founded on or in rock may
be divided into two general categories:
time-dependent deformations and
time-independent deformations.
The three groups include consolidation, swelling,
and creep.
Categories of Rock Mass Deformation:
Deformations that may lead to settlement or
heave of structures founded on or in rock may
be divided into two general categories:
time-dependent deformations and
time-independent deformations.
The three groups include consolidation, swelling,
and creep.
46
27. Bearing Capacity:
the ultimate and allowable bearing stress values
for foundations on rock.
Bearing capacity failures of structures founded
on rock masses are dependent upon joint
spacing with respect to foundation width, joint
orientation, joint condition (open or closed), and
rock type.
27. Bearing Capacity:
the ultimate and allowable bearing stress values
for foundations on rock.
Bearing capacity failures of structures founded
on rock masses are dependent upon joint
spacing with respect to foundation width, joint
orientation, joint condition (open or closed), and
rock type.
47
28. Sliding Stability:
Examples of applicable structures include gravity
dams, coffer dams, flood walls, lock walls, and
retaining structures.
The foundation should be stable with respect to
sliding when, for any potential slip surface.
28. Sliding Stability:
Examples of applicable structures include gravity
dams, coffer dams, flood walls, lock walls, and
retaining structures.
The foundation should be stable with respect to
sliding when, for any potential slip surface.
48
Cut Slope Stability:
for assessing the sliding stability of slopes
formed by excavations in rock or of natural rock
slopes altered by excavation activities.
Typical examples of slopes cut in rock include:
foundation excavations;
construction of project access roads; and
development of dam abutments, spillways, and
tunnel portals.
Cut Slope Stability:
for assessing the sliding stability of slopes
formed by excavations in rock or of natural rock
slopes altered by excavation activities.
Typical examples of slopes cut in rock include:
foundation excavations;
construction of project access roads; and
development of dam abutments, spillways, and
tunnel portals.
49
The type of failure is primarily controlled by the
orientation and spacing of discontinuities within
the rock mass as well as the orientation of the
excavation and the angle of inclination of the
slope.
29. Treating special conditions :
These may be encountered in rock foundations
that cause construction or operation problems.
The type of failure is primarily controlled by the
orientation and spacing of discontinuities within
the rock mass as well as the orientation of the
excavation and the angle of inclination of the
slope.
29. Treating special conditions :
These may be encountered in rock foundations
that cause construction or operation problems.
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These conditions are likely to be encountered
only within certain regions and within certain
rock types, but geotechnical professionals
should be aware of the potential problems and
methods of treatment.
Karst, pseudokarst, and mines which produce
substantial underground cavities; swelling and
squeezing rock, much of which may be described
as a rock but treated as a soil;
These conditions are likely to be encountered
only within certain regions and within certain
rock types, but geotechnical professionals
should be aware of the potential problems and
methods of treatment.
Karst, pseudokarst, and mines which produce
substantial underground cavities; swelling and
squeezing rock, much of which may be described
as a rock but treated as a soil;
51
and gradational soil-rock contacts,
rock weathering, saprolites, and residual soils
which make determination, selection, and
excavation of suitable bearing elevations
difficult.
30. Hydrological properties:
• primary porosity ,
• secondary porosity ,
• hydraulic conductivity (pump tests),
and gradational soil-rock contacts,
rock weathering, saprolites, and residual soils
which make determination, selection, and
excavation of suitable bearing elevations
difficult.
30. Hydrological properties:
• primary porosity ,
• secondary porosity ,
• hydraulic conductivity (pump tests),
52
• transmissivity (pump tests),
• storativity/specific yield (pump tests),
• soluble rock (occurrence of limestone, gypsum,
or dolomite;
• aquifer type (unconfined, confined, leaky
artesian, perched),
• electrical conductivity or resistivity
(geophysical survey).
• transmissivity (pump tests),
• storativity/specific yield (pump tests),
• soluble rock (occurrence of limestone, gypsum,
or dolomite;
• aquifer type (unconfined, confined, leaky
artesian, perched),
• electrical conductivity or resistivity
(geophysical survey).
53
Geophysical testing is often used as part of the
initial site exploration phase of a project and/or
to provide supplementary information collected
by widely-spaced observations.
Geophysical testing is often used as part of the
initial site exploration phase of a project and/or
to provide supplementary information collected
by widely-spaced observations.
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