1. 2-1
LESSON 2 – GEOLOGICAL DATA
COLLECTION and STEREOGRAPHIC
PLOTTING
Learning Outcomes -
List important geological parameters of
discontinuities;
Plot and analyze structural orientation
(stereonet) data.

2. 2-2
Range of rock mass characteristics.

3. 2-3
Scale

4. 2-4
Pervasive discontinuities
Favorably oriented

5. 2-5
Strong rock widely spaced
joints.

6. 2-6Unfavorably oriented discontinuities control

7. 2-7
Definition of Geological Terms
Standard Definitions/Procedures Necessary for:
- Consistency and Compatibility Between Different
Data Collectors
- Facilitate Communication Between Different Parties
- Quantitative Basis for Engineering Evaluation and
Analysis
- Completeness in Data Collection

8. 2-8
Definition of Discontinuity Parameters
Figure 2-2
Page 2-6

9. 2-9
A. - Rock Type
Deere and Miller
Colorado School of Mines Quarterly
(Russell B Travis)

10. 2-10
B Discontinuity Type
Contact - (Continuous and Sometimes Low
Shear Strength e.g. Weathered Paleosurface
Dipping into Cut)
Fault/Shear - (Continuous, Potentially Low
Shear Strength)
Joint - (Cooling in Basalt, Tectonic Effects
Sedimentary/Igneous)
Bedding - (Sedimentary Layering)

11. 2-11
B Discontinuity Type (cont’d)
Flow Banding - (Igneous Flows; May Not be
Weakness)
Foliation/Schistosity/Cleavage - (Metamorphic
Layering)
Vein - (Includes “Healed Joints” - May Not be
Weakness)

12. 2-12
Joints are controlling discontinuities

13. 2-13
Bedding is
controlling
discontinuity
I40, NC/TN

14. 2-14
C Discontinuity Orientation
Dip - Angle of Steepest Inclination of Plane,
Measured Below Horizontal (two digits 00 to 90)
Dip Direction (Dip Azimuth) - Azimuth of the
Line of Dip (three digits 000 to 360)
Strike - Azimuth of a Horizontal Line (90
Degrees to Dip Direction) - Unsuitable for Rock
Slope Engineering

15. 2-15
Definition of Dip, Dip Direction,
Strike

16. 2-16
Structural Compass

17. 2-17
D Discontinuity Spacing
Measure True Spacing in Surface Mapping
Range:
Extremely close spacing (<20 mm)
Extremely wide spacing (>6000 mm)
Line Mapping or Coreholes: Use Terzaghi
Correction for True Spacing

18. 2-18
True and Apparent Spacing
Fracture Set Rock Face
Sapp SappSapp
S
S
S
θ

19. 2-19
Extremely close foliation
spacing
Will strongly influence rock
mass:
• strength
• deformability
• permeability
• excavatability

20. 2-20
E Persistence
Document Visible or Inferred Length
- Range:
Very low (<1 m)
Very high (>20 m)
Document Termination of Joints (0, 1, 2)
Statistical Estimates of Length Distribution (e.g.
Pahl, page 2-8)
Persistence cannot be Measured in Core

21. 2-21
Measurement of Persistence
L
H
(t)
(t)
(t)
(t) (t)
(t)
(c)
(c)
(c)
(c)(c)(c)(c)
(c)
s
S’
Scanline
Í
ś


22. 2-22
Persistence of family of
faults will control abutment
design

23. 2-23
F Irregularity/Roughness
Descriptive
Shape: Roughness:
Stepped Rough
Undulating Smooth
Planar Slickensided
Semi Quantitative - Joint Roughness Coefficient
(JRC)
Rough Undulating JRC 20 e.g. Tension Joints
Smooth Undulating JRC 10 e.g. Foliation/Joints
Smooth Planar JRC 5 e.g. Bedding

24. 2-24
Discontinuity Roughness
Measurement
i2d i8d
id i4d
4d8d
2d
d
Mean dip
1
2
Quantitative approach

25. 2-25

26. 2-26
G Wall Rock Strength - (Joint
Compressive Strength - JCS)
Estimate Compressive Strength Based on:
- Field Classification (ISRM) - Table 2-1:
Range:
Extremely weak (0.25-1MPa)
Extremely strong (>250 MPa)
- Field Testing (Point-Load Test or Schmidt Hammer)
- Laboratory Testing

27. 2-27
H Weathering
ISRM Weathering Classification - Table 2-2
- Fresh
- Slightly weathered
- Moderately weathered
- Highly weathered
- Completely weathered
- Residual soil

28. 2-28
Differential shale weathering

29. 2-29
Chemical decomposition

30. 2-30
I Aperture
Measure Directly, Table 2-1:
Range:
- Very tight (<0.1 mm)
- Cavernous (>1000 mm)

31. 2-31
J Filling/Width
Measure Width (Table 2-2)
Characterize Wall Rock
Infilling Characteristics
- Mineralogy
- Particle Size
- Water Content
- Stiffness

32. 2-32
25 mm thick, continuous clay
infillings (bedding plane shears)

33. 2-33
Controlling structure for slope design
Rocky Point Viaduct, OR

34. 2-34
K Seepage
Document According to Field Sheets
- Tight and dry
- Dry
- Dry, rust staining
- Damp
- Seepage, drops
- Continuous flow

35. 2-35
L Number of Joint Sets
Number of Systematic Joint Sets
- Often three orthogonal sets
- Maximum four or five sets
- Record faults and shears separately from joints and
bedding

36. 2-36
M Block Size/Shape
Use code on Data Collection Sheet
SHAPE SIZE
- Blocky Very large (>8 m3)
- Tabular Large (0.2 – 8 m3)
- Columnar Medium (0.008-0.2 m3)
- Shattered Small (0.0002 – 0.008 m3)
Very small (<0.0002 m3)

37. 2-37Blocky structure

38. 2-38
Refer to Figure 2-2 of Reference Manual on page
2-6

39. 2-39
Geotechnical Mapping
Line Mapping
- Documenting All Structures that Intersect a Tape or
Painted Scan Line
Window (Cell) Mapping
- Document All Structures Within a Representative
Areas or “Windows”

40. 2-40
Geotechnical Drilling

41. 2-41
Diamond Drilling
Triple Tube or Double Tube with a Split Inner
Tube
 Geotechnical Logs - RQD, Recovery, Fracture Frequency, Joint
Angle (Cornerstone of Communication !!!)
Core Photographs & Core Handling
Structural Orientation Data from Drilling
- Oriented Coring - Clay Impression Method
- Borehole Imaging

42. 2-42
Core Photographs

43. 2-43

44. 2-44
Core Orientation – Reference Line
Dip
Side View
Dip Joint
Dip Vector
Top of Core
(In Situ)
End View
Reference Angle

45. 2-45

46. 2-46

47. 2-47
Borehole Televiewer Logging

48. 2-48
Core Orientation – Borehole Camera
Core Unwrapped Core
Dip
Direction
0 90 180 270 360
Dip
Trace of
joint

49. ProjectNo.052-2005Date:May2008
Comparable section of core quality and televiewer data.
Acoustical
Log
Optical
Log
id# Dip DDR
DDR = dip directionBorehole Televiewer Logging