interpretation of rock properties chapter 10 mount pilatus, switzerlandarches national park, utah...

Interpretation of

Rock Properties

Chapter 10

Mount Pilatus, Switzerland Arches National Park, Utah

Lesson 14

FHWA-NHI Subsurface Investigations

Objectives: Interpretation of Rock Properties

Be familiar with charts, equations, and tables for evaluation of rock properties

•Determine validity of rock test results

•Selection of appropriate values

•Perform preliminary design evaluation

Recognize that cracks & fissure in rock mass are as important as intact material between the discontinuities.

2


Interpretation of Rock Properties

Rock involved with highway construction: foundations, slopes, tunnels, and cuts.

Two levels of rock classification:

• Intact Rock (origin, type, age, minerals)

• Rock Mass (discontinuities, joints, fissures)

Combined lab and field test program

3


Grand Canyon, Arizona

4


Intact Rock Classification

Rock Type

Geologic Formation and Age

Indices:

•Specific Gravity, Porosity, Unit Weight, Wave Velocities

•Strength (compressive, tensile, shear)

•Elastic Modulus

5


Major Rock Formations in USA

6


Primary Rock Types by Geologic Origin

Grain

Aspects

Clastic

واریآ

Carbonate

کربناتی

Foliated

ورقه ای

Massive

توده ای

Intrusive

نفوذی

Extrusive

خروجی

Coarse

درشت )زبر(

Conglomerate

Breccia

Limestone

Conglomerate

Gneiss Marble Pegmatite

Granite

Volcanic Breccia

Medium

متوسط

Sandstone

Siltsone

Limestone

Chalk

Schist

Phyllite

Quartzite

Diorite

Diabase

Tuff

Fine

ریز )نرم(

Shale

Mudstone

Calcareous Mudstone

Slate Amphibolite

Rhyotite Basalt

Obsidian

Sedimentary Types

Metaphorphic

Igneous Types

7


Geologic Time Scale

Geologic Time Scale Era Period Epoch Time Boundaries (Years Ago) Holocene - Recent Quaternary 10,000 Pleistocene 2 million Pliocene 5 million Cenozoic Miocene 26 million Tertiary Oligocene 38 million Eocene 54 million Paleocene 65 million Cretaceous 130 million Mesozoic J urassic 185 million Triassic 230 million Permian 265 million Pennsylvanian Carboniferous 310 million Mississippian 355 million Paleozoic Devonian 413 million Silurian 425 million Ordovician 475 million Cambrian 570 million Precambrian 3.9 billion

Earth Beginning 4.7 billion Greenland

8

FHWA-NHI Subsurface Investigations9


Geologic Mapping of Rock Mass Features

10


Index Properties of Intact Rock

Specific Gravity of Solids, Gs

Unit Weight, Porosity, n

Ultrasonic Velocities )Vp and Vs(

Compressive Strength, qu

Tensile Strength, T0

Elastic Modulus, ER )at 50% of qu(

11


Specific Gravity of Rock Minerals

0 1 2 3 4 5 6 7 8

Specific Gravity of Solids, Gs

halitegypsum

serpentinequartz

feldsparchloritecalcite

dolomiteolivinebaritepyrite

galena

Specifi c Gravit ies of Rock Minerals

Reference Value(fresh water)

Common MineralsAverage Gs = 2.70

12


Unit Weights of Rocks

14

16

18

20

22

24

26

28

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Porosity, n

Satu

rate

d U

nit

We

igh

t,T )

kN

/m3(

Dolostone GraniteGraywacke LimestoneMudstone SiltstoneSandstone Tuff

sat =

water [ Gs(1-n) + n]

Gs = 2.80 2.65 2.50

13


Ultrasonic Velocities of Rocks

Seismic Velocities for Intact Rock Materials

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Compression Wave, Vp )m/s(

Sh

ear

Wave,

V s )m

/s(

Limestone Chalk Marble SchistTuff Slate Anhydrite GrandioriteDiorite Gabbro Granite DuniteBasalt Dolostone Mudstone Siltstone

14


Strength of Intact Rocks

Compressive Strength, u = qu

)Direct( Tensile Strength, *T0

)Indirect( Brazilian Strength, T0

Shear Strength,

• Across the intact rock

• Along the planar surface (joints)15


Lab Data on Intact Rocks )Goodman, 1989(

qu T0 ER Ratio Ratio

Intact Rock Material (MPa) (MPa) (MPa) (-) qu/T0 ER//qu

Baraboo Quartzite 320.0 11.0 88320 0.11 29.1 276Bedford Limestone 51.0 1.6 28509 0.29 32.3 559Berea Sandstone 73.8 1.2 19262 0.38 63.0 261Cedar City Tonalite 101.5 6.4 19184 0.17 15.9 189Cherokee Marble 66.9 1.8 55795 0.25 37.4 834Dworshak Dam Gneiss 162.0 6.9 53622 0.34 23.5 331Flaming Gorge Shale 35.2 0.2 5526 0.25 167.6 157Hackensack Siltstone 122.7 3.0 29571 0.22 41.5 241John Day Basalt 355.0 14.5 83780 0.29 24.5 236Lockport Dolomite 90.3 3.0 51020 0.34 29.8 565Micaceous Shale 75.2 2.1 11130 0.29 36.3 148Navajo Sandstone 214.0 8.1 39162 0.46 26.3 183Nevada Basalt 148.0 13.1 34928 0.32 11.3 236Nevada Granite 141.1 11.7 73795 0.22 12.1 523Nevada Tuf f 11.3 1.1 3649.9 0.29 10.0 323Oneota Dolomite 86.9 4.4 43885 0.34 19.7 505Palisades Diabase 241.0 11.4 81699 0.28 21.1 339Pikes Peak Granite 226.0 11.9 70512 0.18 19.0 312Quartz Mica Schist 55.2 0.5 20700 0.31 100.4 375Solenhofen Limestone 245.0 4.0 63700 0.29 61.3 260Taconic Marble 62.0 1.2 47926 0.40 53.0 773Tavernalle Limestone 97.9 3.9 55803 0.30 25.0 570

Statistical Results: Mean = 135.5 5.6 44613 0.29 39.1 372.5 S.Dev. = 93.7 4.7 25716 0.08 35.6 193.8

Note: 1 MPa = 10.45 tsf = 145.1 psi 16


Classification for Rock Material Strength

17


Rock Strength Interrelationships

R =shearstrength

18


Intact Rock Strength Interrelationships

I n t a c t R o c k S p e c i m e n s

0

5

1 0

1 5

2 0

2 5

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0C o m p r e s s i v e S t r e n g t h , q u ) M P a (

Tens

ile St

rength

, T0

)MPa

(

S e d i m e n t a r yM e t a m o r p h i cI g n e o u sT r e n d+ S . E .- S . E .

01.004.00 uq

T

19


Intact Rock Classification

Classification by Uniaxial Compressive

Strength, u

Categorize Rock by its Strength and

Modulus Ratio )ER/u(

Summary plots for Igneous, Sedimentary, and Metamorphic Rock Types

Check on reasonableness of your lab measurements and tests

20


ER-qu Groups for Igneous Rocks

Deere

and

Miller

(1966)

21


ER-qu Groups for Sedimentary Rocks

Deere

and

Miller

(1966)

22


ER-qu Groups for Metamorphic Rocks

Deereand

Miller(1966)

23


EMAX-qu Groups for All Types of Geomaterials

(Tatsuoka and Shibuya, 1992)

24


Illustrative

Cases for

Defining

Rock Shear

Strength for

Cut Slope

25


Rio de Janeiro, Brazil

26


Rock Mass Classifications

RQD - early form of rating rock mass

Geomechanics System - Rock Mass

Rating )RMR( by Bieniawski )1984, 1989(

Q-System - Norwegian Geotechnical

Institute )Barton, et al. 1974(

Geological Strength Index, GSI )Hoek, et

al., 1995(

27


Rock Mass Rating )RMR(

RMR based on five parameters:

• Uniaxial strength, qu

• Rock Quality Designation, RQD

• Spacing of Discontinuities

• Condition of the Discontinuities

• Groundwater Conditions

RMR = R1+R2+R3+R4+R5

Adjustment for Joint Orientation

relative to construction

Rock CityChattanooga, TN

28


0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 300

Unconfined Compressive Strength, qu (MPa)

RM

R R

atin

g R

1

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100

Rock Quality Designation, RQD

RM

R R

atin

g R

2

0

5

10

15

20

25

0.01 0.1 1 10

Joint Spacing (meters)

RM

R R

atin

g R

3

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6Joint Separation or Gouge Thickness (mm)

RM

R R

atin

g R

4 Slightly Rough Weathered

Slickensided Surface or Gouge-Filled

Soft Gouge-Filled

Joint Water Pressure Ratio, u/1 Inflow per 10-m Tunnel Length (Liters/min)

Rough/Unweathered

Rock Mass Rating )RMR(Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]

29


Rock Mass Rating )RMR(Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]

0

5

10

15

20

25

0.01 0.1 1 10

RM

R R

atin

g R

30

5

10

15

20

25

30

35

0 1 2 3 4 5 6

RM

R R

atin

g R

4 Slightly Rough Weathered

Slickensided Surface or Gouge-Filled

Soft Gouge-Filled

0

2

4

6

8

10

12

14

16

0 0.1 0.2 0.3 0.4 0.5 0.6

Joint Water Pressure Ratio, u/1

RM

R R

atin

g R

5

u = joint water pressure

1 = major principal stress

Alternate 2 Defi nit ions

f or Parameter R5

0

2

4

6

8

10

12

14

16

1 10 100 1000

Inflow per 10-m Tunnel Length (Liters/min)

RM

R R

atin

g R

5

Alternate 1 Defi nit ions

f or Parameter R5

Dry

Damp

Wet

Dripping

Flowing

ROCK MASS RATING )RMR( also CSIR System 5

Geomechanics System - (Bieniawski, 1984, 1989) RMR = Ri Geomechanics Classification for Rock Masses i = 1 CLASS DESCRIPTION RANGE of RMR

I Very Good Rock 81 to 100 NOTE: Rock Mass Rating is obtained by summing the five index II Good Rock 61 to 80 parameters to obtain an overal rating RMR. Adjustments for dip III Fair Rock 41 to 60 and orientation of discontinuities being favorable or unfavorableIV Poor Rock 21 to 40 for specific cases of tunnels, slopes, & foundations can also beV Very Poor Rock 0 to 20 considered.

0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 3000

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100

30


NGI- Q Rating of Rock Masses Q-Rating based on 6 parameters:

• Rock Quality Designation, RQD

• Number of Joint Sets, Jn• Roughness of Discontinuities, Jr• Discontinuity Condition/Filling, Ja

• Groundwater Conditions, Jw• Stress Reduction Factor, SRF

Rating of Rock Formation:

SRF

J

J

J

J

RQDQ w

a

r

n

Tucson, AZ

31


N G I Q - S y s t e m R a t i n g f o r R o c k M a s s e s ( B a r t o n , L i e n , & L u n d e , 1 9 7 4 ) N o r w e g i a n C l a s s i f i c a t i o n f o r R o c k M a s s e s Q - V a l u e Q u a l i t y o f R o c k M a s s < 0 . 0 1 E x c e p t i o n a l l y P o o r 4 . D i s c o n t i n u i t y C o n d i t i o n & I n f i l l i n g = J a

0 . 0 1 t o 0 . 1 E x t r e m e l y P o o r 4 . 1 U n f i l l e d C a s e s 0 . 1 t o 1 V e r y P o o r H e a l e d 0 . 7 5 1 t o 4 P o o r S t a i n e d , n o a l t e r a t i o n 1 4 t o 1 0 F a i r S i l t y o r S a n d y C o a t i n g 3 1 0 t o 4 0 G o o d C l a y c o a t i n g 4 4 0 t o 1 0 0 V e r y G o o d 4 . 2 F i l l e d D i s c o n t i n u i t i e s 1 0 0 t o 4 0 0 E x t r e m e l y G o o d S a n d o r c r u s h e d r o c k i n f i l l 4 < 4 0 0 E x c e p t i o n a l l y G o o d S t i f f c l a y i n f i l l i n g < 5 m m 6

S o f t c l a y i n f i l l < 5 m m t h i c k 8

P A R A M E T E R S F O R T H E Q - R a t i n g o f R o c k M a s s e s S w e l l i n g c l a y < 5 m m 1 2 S t i f f c l a y i n f i l l > 5 m m t h i c k 1 0

1 . R Q D = R o c k Q u a l i t y D e s i g n a t i o n = s u m o f c o r e d p i e c e s S o f t c l a y i n f i l l > 5 m m t h i c k 1 5 > 1 0 0 m m l o n g , d i v i d e d b y t o t a l c o r e r u n l e n g t h S w e l l i n g c l a y > 5 m m 2 0

2 . N u m b e r o f S e t s o f D i s c o n t i n u i t i e s ( j o i n t s e t s ) = J n 5 . W a t e r C o n d i t i o n s M a s s i v e 0 . 5 D r y 1 O n e s e t 2 M e d i u m W a t e r I n f l o w 0 . 6 6 T w o s e t s 4 L a r g e i n f l o w i n u n f i l l e d j o i n t s 0 . 5 T h r e e s e t s 9 L a r g e i n f l o w w i t h f i l l e d j o i n t s F o u r o r m o r e s e t s 1 5 t h a t w a s h o u t 0 . 3 3 C r u s h e d r o c k 2 0 H i g h t r a n s i e n t f l o w 0 . 2 t o 0 . 1

H i g h c o n t i n u o u s f l o w 0 . 1 t o 0 . 0 5

3 . R o u g h n e s s o f D i s c o n t i n u i t i e s * = J r

N o n c o n t i n u o u s j o i n t s 4 6 . S t r e s s R e d u c t i o n F a c t o r * * = S R F R o u g h , w a v y 3 L o o s e r o c k w i t h c l a y i n f i l l 1 0 S m o o t h , w a v y 2 L o o s e r o c k w i t h o p e n j o i n t s 5 R o u g h , p l a n a r 1 . 5 S h a l l o w r o c k w i t h c l a y i n f i l l 2 . 5 S m o o t h , p l a n a r 1 R o c k w i t h u n f i l l e d j o i n t s 1 S l i c k a n d p l a n a r 0 . 5 F i l l e d d i s c o n t i n u i t i e s 1 * * N o t e : A d d i t i o n a l S R F v a l u e s g i v e n* N o t e : a d d + 1 i f m e a n j o i n t s p a c i n g > 3 m f o r r o c k s p r o n e t o b u r s t i n g , s q u e e z i n g

a n d s w e l l i n g b y B a r t o n e t a l . ( 1 9 7 4 )

SRF

J

J

J

J

RQDQ w

a

r

n

32

FHWA-NHI Subsurface Investigations33


Geological Strength Index, GSI Developed by Hoek, Kaiser, & Bawden

)1995(, Hoek & Brown )1997(.

GSI from Q-system:

GSI from Geomechanics system where RMR > 25:

Chart approach based on structure & surface quality

44log9

a

r

n J

J

J

RQDGSI

4

1

10i

iRGSI

34


GSI Evaluation from Chart

Hoek (2000)

35


Strength of Rock Masses

a

ubu sm

'

'' 331

Depends on Intact Rock Material and Rock Mass Jointing Intact Rock

Uniaxial Compression Strength, qu = u

Rock Material Type using parameter mi

Fractured Rock Characteristics (in terms of GSI) Parameters mb and s and exponent "a"

Obtain Mohr-Coulomb Strength Envelope from:

36


Rock Strength: mi parameter

37


Strength of Fractured Rock Masses

a

ubu sm

'

'' 331

Parameter: mb = mi exp [(GSI-100)/28]

For GSI > 25: s = exp [(GSI-100)/9] exponent a = 0.5

For GSI < 25: s = 0 exponent a = 0.65 - (GSI/200)

38



Rock Mass Strength - Hoek & Brown )Sept. J GE 1980(

PROBLEM DATA Geological Strength Index, GSI (Hoeg, et al. 1995) GSI = 43 Equivalent Q = 0.895 qu (MPa)= 55 m/mi Reduction = 0.131 mi = 7 s (Rock Mass) = 0.00178 GWT depth(m) = 8 m (Rock Mass)= 0.91411 (kN/m3) = 26.5 Depth (m) = 25

MOHR-COULOMB CRITERION

Depth 3 1' uo 3' 1' q p' Ratio Secant Incremental Parameters

z (m) (kPa) (kPa) (kPa) (kPa) (kPa) (kPa) (kPa) q/p' ' c', kPa '========================================================================================================================= ===========

0 0 2318 0 0 2318 1159 1159 1.000 90.05 132.5 3602 0 133 3602 1735 1867 0.929 68.3 372 54.4

10 265 4454 20 245 4454 2104 2350 0.896 63.6 473 50.015 397.5 5010 69 329 5010 2340 2669 0.877 61.3 547 47.620 530 5522 118 412 5522 2555 2967 0.861 59.4 604 46.025 662.5 6001 167 496 6001 2752 3248 0.847 57.9 659 44.7

Excel Spreadsheet of Generated Principal Stresses

39



Hoek-Brown Rock Mass Model

0

1000

2000

3000

4000

5000

6000

0 2000 4000 6000 8000

Normal Stress, (kPa)

Sh

ea

r S

tre

ss

,

(kP

a)

40



Hoek-Brown Rock Mass Model

0

1000

2000

3000

0 1000 2000 3000 4000

p' = 0.5 ('

' (kPa)

q

=

0.5

(1-

3)

(kP

a)

41


Strength of Rock Massesmi

42


Strength of Rock Masses

mi

c'/qu

43


Attentione! Else you'll go to "the Rock"

44


Deformation Properties of Fractured Rock Masses

45


Equivalent Modulus of Rock Masses )Table 10-7(

46


Allowable Bearing Stresses on Rock Masses

F o u n d a t i o n s o n F r a c t u r e d R o c k F o r m a t i o n s

0

5

1 0

1 5

2 0

2 5

3 0

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

R o c k Q u a l i t y D e s i g n a t i o n , R Q D

Allowable

Bearing

Stress q

a )MPa(

P e c k , e t a l . ( 1 9 7 4 )

A p p r o x i m a t i o n

N o t e : U s e m a x i m u m q a < q u

w h e r e q u = c o m p r e s s i v e s t r e n g t ho f i n t a c t r o c k s p e c i m e n s

)130/(1

)16/(1)(

RQD

RQDMPaq ALLOWABLE

N O T E : 1 M P a = 1 0 t s f

47


Objectives: Interpretation of Rock Properties

Be familiar with charts, equations, and tables for evaluation of rock properties

•Determine validity of rock test results

•Selection of appropriate values

•Perform preliminary design evaluation

Recognize that cracks & fissure in rock mass are as important as intact material between the discontinuities.

48


Mount Rainer, Washington

49

interpretation of rock properties chapter 10 mount pilatus, switzerlandarches national park, utah...

Documents

rock material strength

intact rock origin

levels of rock classification

qu tensile strength

vs compressive strength

t0 shear strength

intact material

qu direct tensile strength