This document provides an overview of engineering geology and rock mechanics. It discusses fundamentals such as lithology, rock structures, weathering, and rock mass classification systems. It also presents a case study on the 1928 failure of the St. Francis Dam in California, which was caused by unsuitable geological conditions including weakness along the San Francisquitto fault that were not properly considered in the dam's design and construction. The case study demonstrates the importance of engineering geological considerations for civil works.

1. National University of
Malaysia
Engineering Geology
(A Glimpse of Engineering Geology
and Rock Mechanics)
Wan Zuhairi Wan Yaacob (Assoc. Prof, PhD)
Faculty of Science and Technology
National University of Malaysia
43600 Bangi, Selangor, MALAYSIA.
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2. Contents
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• Introduction
• Fundamentals of Engineering Geology
• Case studies
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3. National University of
Malaysia
Introduction
ALL Civil Engineering works
are carried out on or in the
ground
Hoover Dam, Colorado
Tunnel in Wales, UK
Underground mining
“An engineer is a person who can do for one dollar what any fool
can do for two” Matthewson, 1981.
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4. Geology & Civil Engineering
National University of
Malaysia
GEOTECHNOLOGY
Engineering in earth materials
Engineering Geology
(Geological Engineering)
Civil Engineering
Mining Engineering
A. Roberts (1977). Geotechnology: An Introduction text for students and engineers.
B. Pergamon Press.
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5. ENGINEERING GEOLOGY
(Geological Engineering)
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Engineering geologist as a “two-faced” professional looking back
at geologic processes and forward to engineering products
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6. Fundamentals of Engineering Geology
• Lithology / Rock Type
• Rock Structure
• Rock Weathering
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Rock Type
Rock weathering
fresh
weathered
Rock structures
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7. National University of
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Rock Type
(Lithology)
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8. 3 Major Rock Types
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9. Definitions of rocks:
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• Architect
– Rock is a type of building material, dimension stone
• Engineer
– Rock as a hard or brittle material that requires
BLASTING to excavate.
– A permanent, durable material for erosion control
or engineering uses.
• Geologist
– Rock is an earth material produced by the rock
forming processes; OR
– Rocks are natural earth materials composed of
aggregates of one or more minerals
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10. Two main engineering properties of
rock :
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• (1) Rock Substance
– The properties of the intact, unfractured rock
specimen.
• (2) Rock mass
– The entire rock body
– Incl. fractures and discontinuities
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11. National University of
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Rock Substance
Rock mass
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12. National University of
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Rock material
View under the microscope
Interlocking of minerals
Cemented grains/minerals
Core samples
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13. Rock Mass
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Rock materials + discontinuities (i.e. joints, fractures, faults, folds, planes)
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14. Strong vs weak rocks
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Malaysia
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15. National University of
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Rock Structures
(or discontinuities)
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16. Earth forces & the deformation
of rocks
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• Stresses (TEGASAN); (P = F/A)
– Compression
• Acts to compress objects
– Tensional
• Acts to stretch objects
– Shear
• Complex kind of stress
• Opposite sites
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17. Elastic-plastic deformation
(In Laboratory)
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Material A
Plastic
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fracture
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18. In the field…
SESAR / FAULT
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LIPATAN / FOLD
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19. TYPE ???
WHY ???
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20. National University of
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21. National University of
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How to describe discontinuities:
•
•
•
•
•
•
•
•
•
•
1. Orientation
2. Spacing
3. Persistence
4. Roughness
5. Wall strength
6. Aperture
7. Filling
8. Seepage (water)
9. Number of sets
10. Block size
1
2
3
6
7
4
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22. National University of
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Discontinuity and dams
• Orientation (1)
Axis of dam
(favorable)
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(unfavorable)
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23. Discontinuity and slope
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• Orientation (2)
Inclination away from
the road (stable)
Inclination towards the
road (less stable)
Unstable block
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24. National University of
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Weathering
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25. National University of
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Weathered Granit
(Grade III-IV)
Fresh Granit (Grade I)
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26. Rock
Soil
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27. National University of
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28. National University of
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Engineering Rock Classification
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29. Rock mass classification
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• Rock mass classification is a
means of evaluating the
quality (strong/weak) and
expected behavior of rock
masses based on the most
important parameters that
influence the rock mass
quality.
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30. 1. Rock Quality Designation (RQD) system
(Deere et al, 1967).
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Malaysia
• The cumulative length of intact core
pieces longer than 10cm in a run divided
by the total length of the core run.
Sum of lengths of core sticks > 10 cm long x 100
Total length of core run
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31. Core recovery
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• The ratio of the length of core recovered
to the length drilled
• Ranges from 0% (no core recovery) to
100% (total recovery)
% Core recovery = total length of core samples (1,2,3) x 100
core run length
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32. National University of
Malaysia
Core recovery
10cm
= (2.0)/(2.0) x 100%
= 100%
2.0m
RQD
= (2.0)/(2.0) x 100%
= 100% (Excellent!)
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33. National University of
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Rock Quality Designation
RQD
<25%
Very Poor
25-49%
Poor
50-74%
Fair
75-89%
Good
90-100%
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Rock Quality Classification
Excellent
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34. 2. ROCK MASS RATING (RMR)
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Malaysia
• Proposed by Bieniawski (1981)
• The South African Geomechanics Classification (SAGC)
RMR = JA1 + JA2 + JA3 + JA4 + JA5 + JB
• SIX parameters are required:
1. Uniaxial compressive strength (JA1)
2. RQD (JA2)
3. Discontinuity spacing (JA3)
4. Conditions of the discontinuities (JA4)
5. Groundwater (flow and general conditions) (JA5)
6. Rating adjustment for discontinuity orientations (JB)
• Based on ratings (total of 6 ratings)
• Total ratings (0-100) will give rock mass classes (I to V).
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35. RMR
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36. National University of
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Case study: St. Francis Dam Failure
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37. National University of
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dam
CASE STUDY: St. Francis Dam, US
•12 March 1928
•500 dead
•Geological factors
•The science of Eng. Geol
dwzwy2004_2005

38. National University of
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dam
Dipping 50o
San Francisquito fault: a branch of
San Andreas fault
•12 March 1928
•500 dead
•Geological factors
•The science of Eng. Geol
dwzwy2004_2005
An engineering geologist knows a dam site better !!

39. National University of
Malaysia
• “this substrate was totally inappropriate
for a dam footing, and failure of
fractured and weathered conglomerate
was the major cause of the dam failure”.
• “Don’t blame anyone else, you just
fasten it on me. If there was an error in
human judgment, I was the human.”
(William Mulholland, dam’s chief engineer & architect).
dwzwy2004_2005

40. National University of
Malaysia
Thank you
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