General Geology for CE- Structural and Rock Mechanics

1. STRUCTURAL
GEOLOGY AND
ROCK
Chapter 4

2. STRUCTURAL GEOLOGY
✓ The branch of geology that deals with the form, arrangement,
and internal structure of rocks and especially with the description,
representation and analysis of structures, chiefly on a moderate
to a small scale. The subject is similar to tectonics, but the latter
is generally used for broader regional or historical phases.
✓ This is very important in the field of
Civil Engineering since it is the basis of
construction projects for buildings,
bridge, dams, roads, etc. and it serves
as a tool for prevention and mitigation
in the control of geologic risks.

3. IMPORTANT TERMS :
✓ a layer of sediments or
rocks such as coal, that
extends under a large area
and has a distinct set of
characteristics that
distinguish it form other
layers below and above it.
The bottom of a body of
water such as lake, stream
or ocean.
1. BED

4. 2. STRATA
✓ is a layer of rock or sediment characterized by certain
lithologic properties or attributes that distinguish if from
adjacent layers from which it is separated by visible surfaces
known as either bedding surfaces or bedding planes.

5. 3. STRATIGRAPHY
✓ is a branch of geology
concerned with the study of
rock layers and layering.
✓ It has three related
subfields: lithostratigraphy,
biostratigraphy, and
chronostratigraphy.
✓ including their
composition, age, and
spatial distribution.

6. 4.OUTCROP
✓ define as an exposure of a solid rock on the
surface of the Earth.
5. AZIMUTH
✓ a compass direction of the line measured in
degrees (0° - 360° clockwise from North with
(North = 0°, East = 90°, South = 180°, and West =
270°)

7. 6. QUADRANT
✓ a compass direction measured 0° to 90°
form north or south.

8. AZIMUTH QUADRANT

9. VIEWS
2 TYPES OF VIEWS
1. MAP VIEW
2. CROSS - SECTIONAL VIEW

10. 1. MAP VIEW
✓ also known as the top
view, it is the bird's eye
point of view of the
Earth's surface.
2. CROSS - SECTIONAL VIEW
✓ representation on
geometry on a plane
prependicular to the Earth's
surface.

11. ATTITUDE OF BEDS

12. ✓ ATTITUDE a general term for the
orientation of a line or plane.
✓ A three dimensional orientation of planar
and linear features such as a bed, a joint, a
hornblende needle or a fold.
Attitude of beds can be classified into two:
1. PLANAR ATTITUDE
2. LINEAR ATTITUDE

13. 1. PLANAR ATTITUDE
✓ is defined by the strike and dip, strike and dip describe the
orientation of a plane in space.
✓ Example : bedding, fault, fold axial plane, layering in lava, etc.
STIKE AND DIP METHOD
✓ this system is used to describe the orientation of inclined bedding which
is named after the two important principal components in describing 3D
spatial orientation : Srike and Dip.
• STRIKE (Trend )
✓ refers to the line formed by the
intersection of a horizontal plane
and an inclined surface.
✓ generally express as an
angle relative to north
( i.e. N 40° E )

14. • DIP ( Inclined )
✓ is the angle between that horizontal plane such as the
top of a block and the tilted surface (the geologic contact
between the layers).
✓ DIRECTION OF A DIP
• Shallow Dip (0° to 20°)
• Moderate Dip (20° to
50°)
• Steep Dip (50° to 90°)
✓ may express in degree, gradient, or percentage.
Example :
80°
N
80° is the amount
N is the direction
– a direction along which a bed dips
and is perpendicular to the strike
line.

17. 2. LINEAR ATTITUDE
✓ the attitude of linear structure is defined by the Trend and
Plunge ( together they define a vector ).
✓ also defined by their pitch/rake on a given plane.
Pitch / Rake: The acute angle between the line and the
strike of the plane on which the line lies.
✓ Example : Fold axis, hingeline, intersection of two planes,
stretched pebbles, etc.

18. Geologists use a Brunton or Clino Compass to measure
a strike and dip.
DETERMINING THE ATTITUDE OF BEDS

20. TOOLS FOR MEASURING ANGLES AND DIRECTION
OF GEOLOGICAL FEATURES
BRUNTON
COMPASS
✓ is an specialized
instrument used widely by
those needling to make an
accurate degree and angle
measurements in the field.
✓ Brunton Pocket Transit
✓ David W. Brunton, a
Canadian geologist invented it in
1984

21. PARTS OF BRUNTON'S
COMPASS
• Mirror
• Lift pen for needle
• Compass Card
• Sighting Arm
• Needle
• Bull's Eye Level
• Clinometer Level

22. OUTCROP

23. ✓ a rocky exposition on the Earth's surface but
usually occurs as vertical walls (cliffs, quarries,
mine faces, road sections, etc.)
✓ generally made up of some vegetation on
the top

24. OUTCROPS PATTERN
✓ FLAT - LYING BED ✓ PLUNGING FOLDS
✓ RULES OF V'S
Beds that are horizontal
or almost horizontal are
known as flat - flying
beds.
Plunging fold map pattern
create zigzag patterns that
shift direction at the fold
hinges.
visual, qualitative method to determine dip
direction by examining the map pattern of the
contact between two dipping units as it crosses as
a stream or a valley.

25. RULES OF V'S

27. TWO KINDS OF OUTCROPS
NATURAL OUTCROP OUTCROP CAUSED BY HUMAN
ACTIVITIES
Many human activities take
place in our country and it is
undeniable that they have
an impact on many things
such as construction of new
roads, which cause
Outcrops.
commonly found in
steep hillsides,
mountain ridges and
tops, river banks, and
technically active
areas.

28. Natural Outcrop
OUTCROP CAUSED BY
HUMAN ACTIVITIES

29. SALAMAT HAN PAMATI
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