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Engineering Geology
(Introduction)

Engineering geology is the application of
the geological sciences to
engineering study for the purpose of
assuring that the geological factors
regarding the location, design, construction,
operation and maintenance
of engineering works are recognized and
accounted for.
What’s the purpose of Engineering
Geology on Engineering students?
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Geology provides a systematic knowledge of construction material, its
occurrence, composition, durability and other properties. Example of such
construction materials is building stones, road metal, clay, limestones and
laterite.
The knowledge of the geological work of natural agencies such as water, wind,
ice and earthquakes helps in planning and carrying out major civil engineering
works. For example the knowledge of erosion, transportation and deposition
helps greatly in solving the expensive problems of river control, coastal and
harbour work and soil conservation.
Ground water is the water which occurs in the subsurface rocks. The
knowledge about its quantity and depth of occurrence is required in connection
with water supply, irrigation, excavation and many other civil engineering works.
In the study of soil mechanics, it is necessary to know how the soil materials
are formed in nature.
The cost of engineering works will considerably reduced of the geological
survey of the area concerned is done before hand.
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The foundation problems of dams, bridges and buildings are directly
concerned with the geology of the area where they are to be built. In
these works drilling is commonly undertaken to explore the ground
conditions. Geology helps greatly in interpreting the drilling data.
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In tunneling, constructing roads, canals, docks and in determining the
stability of cuts and slopes, the knowledge about the nature and
structure of rocks is very necessary.
Before staring a major engineering project at a place, a detailed
geological report which is accompanied by geological maps and
sections, is prepared. Such a report helps in planning and constructing
the projects.
The stability of civil engineering structure is considerably increased if
the geological feature like faults, joints, bedding planes, folding
solution channels etc. in the rock beds are properly located and
suitably treated.
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Earth’s Size & Shape
I. Model
A
representation of an object, a
process, or a phenomenon.
Ex.
– Globe – best, most to scale model
of the Earth
– Computer Climate
models/Simulations
II. A System

Part of the Universe that can be studied
separately
–
Closed System- a system in which
energy can enter or leave, but matter
cannot
–
Open System- a system in which
there is a free exchange of both
energy & matter between the system
& its surroundings.
The Structure of the Earth
Structure of the Earth
Mantle

The Earth is made
up of 3 main
layers:
–
–
–
Core
Mantle
Crust
Crust
Outer core
Inner core
The Crust

This is where we live.

The Earth’s crust is made
of:
Continental Crust
Oceanic Crust
- thick (10-70km)
- thin (~7 km)
- dense (sinks under continental
crust)
- young
- buoyant (less dense than
oceanic crust)
- mostly old
III. Structure of the Earth
A. Inner Core - layer of the Earth
composed of solid iron & nickel
B. Outer Core - layer of the Earth
composed of liquid iron & nickel
Structure of the Earth Cont’
C. Mantle - largest Earth layer
 composed of silicon, oxygen,
magnesium, & iron
D. Crust - outer most layer of Earth
 the deepest mines & caves go no further
than the crust
 thicker under the continents than the
ocean
Layers of the Earth
IV.Temperatures Below the
Surface
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Deep caves stay about the same
temperature all year

From 0 m to 20 m below, a cave usually
remains equal to the avg. yearly
temperature

Every 40 m below the 1st 20 m, the
temperature in a cave 10C for each 40
m (120ft)
Heat is from:

Radioactive Minerals
– Ex Uranium & Thorium

Compression of the crust by gravity
V. Earth’s Shape
A. Evidence that Earth is
Spherical
1. The mast of a ship is
the 1st part to appear
over the horizon &
the last to disappear.
Earth From Space
2.Photographs
of Earth from
space
Earth’s Shape Cont’
3. An eclipse of the moon occurs
when Earth's shadow falls on the
moon

The shadow is
always an arc of
a circle
http://www.rit.edu/~andpph/eclipse-01-20-00.htm l
Earth’s Shape Cont’
4. Ships sailing north or south observed
changes in the nighttime sky.

North Star appears higher in the sky as
a ship travels north

Ships sailing south lose sight of the Big
Dipper & begin to see the Southern
Cross
B. Oblate Spheroid

Sphere that is slightly flattened at the
poles & bulged at the equator

Caused by Earth's rotation
C. Weight on Earth
VI. Earth’s Density
A.
Density – The amount of matter
(mass) in a given space (volume)
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Average density = 5.5 g/cm3
VII. Measuring Earth's Circumference
A. Eratosthenes (er uh Tos thuh neez)
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Of Greek heritage, born in Cyrene,
now
Shah hat, (Libya)
Studied at Alexandria & Athens
Appointed Director of the Alexandrian
Library, 236 BC
Eratosthenes Cont’
Lived in Egypt
 1st Scientific Measurement of Earth’s
Circumference
 Went blind 195 BC
 Starved himself to death 194 BC
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Facts Eratosthenes knew:

At noon on June 21st (Summer
solstice):
The sun casts a shadow of 7.2o
from an obelisk in Alexandria
The sun cast no shadow in a well
in Syene (called Aswan today)
Facts Eratosthenes knew:
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Believed the suns rays hit the Earth as
parallel lines
Eratosthenes figured Syene was due south
of Alexandria (He was slightly off on this one)
Distance between Syene & Alexandria
(925km) slightly off
Thought both cities were on the same line of
longitude (off on this by 30)
VIII. Types of Data

Qualitative – data that is relative but not
numeric.
– Ex. The color of an object or stating
someone is tall or taller than another
person

Quantitative – data where a numeric
measurement or a count of objects has
been made
IX. 4 Spheres/Subdivisions of
Earth
1.
2.
3.
4.
Atmosphere
Geosphere
Hydrosphere
Biosphere
1. Atmosphere

Atmos- Greek, Meaning vapor
– Ozone- O3, protects Earth from Sun’s
harmful UV rays
– Oxygen & Carbon Dioxide provided for
living things
– Water vapor forms
clouds
2. Geosphere

Geo –Greek, meaning Earth
– Rocks, Mountains, Beaches
3. Hydrosphere

Hydro- Greek meaning water
– All the water of the Earth’s System
Oceans
Glaciers
Groundwater
Rivers
Lakes
4. Biosphere

Bio- Greek meaning Life
– All forms of life on Earth from microscopic
to Human