fundamentals of engineering geology

National University of Malaysia

1

Engineering Geology (A Glimpse of Engineering Geology

and Rock Mechanics)

28-Jan-14

Wan Zuhairi Wan Yaacob (Assoc. Prof, PhD) Faculty of Science and Technology

National University of Malaysia 43600 Bangi, Selangor, MALAYSIA.


• Introduction

• Fundamentals of Engineering Geology

• Case studies

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Contents


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Introduction

ALL Civil Engineering works are carried out on or in the ground

Hoover Dam, Colorado Underground mining

“An engineer is a person who can do for one dollar what any fool can do for two” Matthewson, 1981.

Tunnel in Wales, UK


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Geology & Civil Engineering

GEOTECHNOLOGY Engineering in earth materials

Engineering Geology (Geological Engineering)

Mining Engineering

Civil Engineering

A. Roberts (1977). Geotechnology: An Introduction text for students and engineers.

B. Pergamon Press.


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ENGINEERING GEOLOGY

(Geological Engineering)

Engineering geologist as a “two-faced” professional looking back at geologic processes and forward to engineering products


• Lithology / Rock Type

• Rock Structure

• Rock Weathering

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Fundamentals of Engineering Geology

Rock Type

Rock structures

Rock weathering

fresh

weathered


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Rock Type (Lithology)


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3 Major Rock Types


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Definitions of rocks:

• 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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Two main engineering properties of rock :

• (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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Rock Substance

Rock mass


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Rock material

Interlocking of minerals Cemented grains/minerals

Core samples

View under the microscope


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Rock Mass

Rock materials + discontinuities (i.e. joints, fractures, faults, folds, planes)


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Strong vs weak rocks


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Rock Structures (or discontinuities)


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Earth forces & the deformation of rocks

• 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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Elastic-plastic deformation (In Laboratory)

Plastic fracture

Material A


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In the field…

SESAR / FAULT LIPATAN / FOLD


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TYPE ??? WHY ???


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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

4 5

6 7


• Orientation (1)

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Discontinuity and dams

Axis of dam

(favorable) (unfavorable)


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Discontinuity and slope

Inclination towards the road (less stable) Inclination away from

the road (stable)

• Orientation (2)

Unstable block


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Weathering


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Fresh Granit (Grade I)

Weathered Granit

(Grade III-IV)


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Ro

ck

So

il


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Engineering Rock Classification


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Rock mass classification

• 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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1. Rock Quality Designation (RQD) system

(Deere et al, 1967).

• 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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Core recovery

• 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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2.0m

10cm Core recovery = (2.0)/(2.0) x 100% = 100%

RQD = (2.0)/(2.0) x 100% = 100% (Excellent!)


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RQD

Rock Quality Classification

<25%

Very Poor

25-49%

Poor

50-74%

Fair

75-89%

Good

90-100%

Excellent

Rock Quality Designation


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2. ROCK MASS RATING (RMR)

• Proposed by Bieniawski (1981)

• The South African Geomechanics Classification (SAGC)

• 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).

RMR = JA1 + JA2 + JA3 + JA4 + JA5 + JB


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RMR


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Case study: St. Francis Dam Failure


dwzwy2004_2005

dam

CASE STUDY: St. Francis Dam, US

•12 March 1928 •500 dead •Geological factors •The science of Eng. Geol


dwzwy2004_2005

dam

An engineering geologist knows a dam site better !!

•12 March 1928 •500 dead •Geological factors •The science of Eng. Geol

San Francisquito fault: a branch of San Andreas fault

Dipping 50o


dwzwy2004_2005

• “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).


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Thank you

fundamentals of engineering geology

Education