1. Interpretation of Rock Properties
Lesson 14
Chapter 10
Interpretation of Rock Properties
Mount Pilatus, Switzerland
Arches National Park, Utah

2. 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.
FHWA-NHI Subsurface Investigations

3. 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
FHWA-NHI Subsurface Investigations

4. FHWA-NHI Subsurface Investigations
Grand Canyon, Arizona
FHWA-NHI Subsurface Investigations

5. Intact Rock Classification
Rock Type
Geologic Formation and Age
Indices:
Specific Gravity, Porosity, Unit Weight, Wave Velocities
Strength (compressive, tensile, shear)
Elastic Modulus
FHWA-NHI Subsurface Investigations

6. Major Rock Formations in USA
FHWA-NHI Subsurface Investigations

7. Primary Rock Types by Geologic Origin
Sedimentary Types
Metaphorphic
Igneous Types
Grain
Aspects
Clastic
آواری
Carbonate
کربناتی
Foliated
ورقه ای
Massive
توده ای
Intrusive
نفوذی
Extrusive
خروجی
Coarse
درشت (زبر)
Conglomerate
Breccia
Limestone
Gneiss
Marble
Pegmatite
Granite
Volcanic Breccia
Medium
متوسط
Sandstone
Siltsone
Chalk
Schist
Phyllite
Quartzite
Diorite
Diabase
Tuff
Fine
ریز (نرم)
Shale
Mudstone
Calcareous Mudstone
Slate
Amphibolite
Rhyotite
Basalt
Obsidian
FHWA-NHI Subsurface Investigations

8. FHWA-NHI Subsurface Investigations
Geologic Time Scale
Greenland
FHWA-NHI Subsurface Investigations

9. FHWA-NHI Subsurface Investigations

10. Geologic Mapping of Rock Mass Features
FHWA-NHI Subsurface Investigations

11. Index Properties of Intact Rock
Specific Gravity of Solids, Gs
Unit Weight, g
Porosity, n
Ultrasonic Velocities (Vp and Vs)
Compressive Strength, qu
Tensile Strength, T0
Elastic Modulus, ER (at 50% of qu)
FHWA-NHI Subsurface Investigations

12. Specific Gravity of Rock Minerals
FHWA-NHI Subsurface Investigations

13. FHWA-NHI Subsurface Investigations
Unit Weights of Rocks
FHWA-NHI Subsurface Investigations

14. Ultrasonic Velocities of Rocks
FHWA-NHI Subsurface Investigations

15. Strength of Intact Rocks
Compressive Strength, su = qu
(Direct) Tensile Strength, *T0
(Indirect) Brazilian Strength, T0
Shear Strength, t
Across the intact rock
Along the planar surface (joints)
FHWA-NHI Subsurface Investigations

16. Lab Data on Intact Rocks (Goodman, 1989)
FHWA-NHI Subsurface Investigations

17. Classification for Rock Material Strength
FHWA-NHI Subsurface Investigations

18. Rock Strength Interrelationships
shear
strength
FHWA-NHI Subsurface Investigations

19. Intact Rock Strength Interrelationships
FHWA-NHI Subsurface Investigations

20. Intact Rock Classification
Classification by Uniaxial Compressive Strength, su
Categorize Rock by its Strength and Modulus Ratio (ER/su)
Summary plots for Igneous, Sedimentary, and Metamorphic Rock Types
Check on reasonableness of your lab measurements and tests
FHWA-NHI Subsurface Investigations

21. ER-qu Groups for Igneous Rocks
Deere
and
Miller
(1966)
FHWA-NHI Subsurface Investigations

22. ER-qu Groups for Sedimentary Rocks
Deere
and
Miller
(1966)
FHWA-NHI Subsurface Investigations

23. ER-qu Groups for Metamorphic Rocks
Deere
and
Miller
(1966)
FHWA-NHI Subsurface Investigations

24. EMAX-qu Groups for All Types of Geomaterials
(Tatsuoka and Shibuya, 1992)
FHWA-NHI Subsurface Investigations

25. Illustrative Cases for Defining Rock Shear Strength for Cut Slope
FHWA-NHI Subsurface Investigations

26. FHWA-NHI Subsurface Investigations
Rio de Janeiro, Brazil
FHWA-NHI Subsurface Investigations

27. 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)
FHWA-NHI Subsurface Investigations

28. FHWA-NHI Subsurface Investigations
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 City
Chattanooga, TN
FHWA-NHI Subsurface Investigations

29. FHWA-NHI Subsurface Investigations
Rock Mass Rating (RMR)
Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
FHWA-NHI Subsurface Investigations

30. FHWA-NHI Subsurface Investigations
Rock Mass Rating (RMR)
Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
FHWA-NHI Subsurface Investigations

31. 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:
Tucson, AZ
FHWA-NHI Subsurface Investigations

32. FHWA-NHI Subsurface Investigations

33. FHWA-NHI Subsurface Investigations

34. 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
FHWA-NHI Subsurface Investigations

35. GSI Evaluation from Chart
Hoek (2000)
FHWA-NHI Subsurface Investigations

36. Strength of Rock Masses
Depends on Intact Rock Material and Rock Mass Jointing
Intact Rock
Uniaxial Compression Strength, qu = su
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:
FHWA-NHI Subsurface Investigations

37. Rock Strength: mi parameter
FHWA-NHI Subsurface Investigations

38. Strength of Fractured Rock Masses
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 = (GSI/200)
FHWA-NHI Subsurface Investigations

39. Strength of Fractured Rock Masses
Excel Spreadsheet of Generated Principal Stresses
FHWA-NHI Subsurface Investigations

40. Strength of Fractured Rock Masses
FHWA-NHI Subsurface Investigations

41. Strength of Fractured Rock Masses
FHWA-NHI Subsurface Investigations

42. Strength of Rock Massesmi 
FHWA-NHI Subsurface Investigations

43. Strength of Rock Masses
c'/qu mi
FHWA-NHI Subsurface Investigations

44. Attentione! Else you'll go to "the Rock"
FHWA-NHI Subsurface Investigations

45. Deformation Properties of Fractured Rock Masses
FHWA-NHI Subsurface Investigations

46. Equivalent Modulus of Rock Masses (Table 10-7)
FHWA-NHI Subsurface Investigations

47. Allowable Bearing Stresses on Rock Masses
FHWA-NHI Subsurface Investigations

48. 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.
FHWA-NHI Subsurface Investigations

49. FHWA-NHI Subsurface Investigations
Mount Rainer, Washington
FHWA-NHI Subsurface Investigations