Introduction of Engineering Geology

Bindusara TS
Assistant Professor
Civil Engineering Department
Sreenidhi Institute of Science and Technology, Hyderabad

UNIT -1
INTRODUCTION
Eng- Geo [6K473]-Unit1 2

4Eng- Geo [6K473]-Unit1
Geology plays a very important role in the field of
civil engineering.
 It provides knowledge about materials
used for construction.
 Its knowledge is helpful for constructing dams.
 Geotechnical engineers needs knowledge about this
subject for excavation work (digging work).

 Its knowledge is required for foundation faults.
 For design of highways and roads.
 In construction of tunnels.
 Soil tests are done before any project.
 Its knowledge is helpful for river control and shipping
work.
 Nature of soil materials can be find out.

GEOLOGY
Geology is the science of the earth
GEO=Earth, LOGY=Study of science
• It deal with the study of Origin , age, interior structure,
and history of earth
• Evolution and modification of various surface features
like rivers, mountains and Lakes.
• Material make ups the earth.

Main and Allied Branch of Geology
Main Branch Allied Branch
Physical Geology Engineering Geology
Mineralogy Mining Geology
Petrology Geophysics
Structural Geology Geohydrology
Historical Geology Geochemistry
Palaeontology
Economic Geology

Physical Geology
This is also called as Dynamic geology or Geomorphology.
 Physical Geology deals with the different Physical feature of
the earth such as Mountain, rivers, lakes, glaciers and
volcanoes.
 It also deals with different changes occurs on earth surface
like marine, formation or disappearance of rivers, spring and
lakes.

Physical Geology
 Natural phenomena like land slides, earth quake and
weathering.
 Geological works of wind glaciers river oceans ground water
and their role in constantly moulding of earth surface.
9Eng.- Geo [6K473]-Unit1

Mineralogy
This deals with the study of minerals.
Mineralogy deals with the detailed mode of formation,
composition, occurrence, types, association properties uses
etc .

Mineralogy
Civil Engineering point of view
The strength and durability of the material depends on
chemical composition. The quartzite and marble resemble
one another in shine colour and appearance but quartzite by
virtue of its mineral composition is very hard tough, strong
and durable while the marble disintegrates and
decomposition in a short period because of its mineral
composition and properties.

Petrology
Petro =Rock, Logos =Study.
Petrology deals with study of Rocks .
 The earth crust is also called as lithosphere, is made of
different types of rocks. Petrology deals with the
formation, structure, texture, composition, occurrence,
types etc.

Petrology

Petrology
The composition and texture characteristics of rocks
primarily contribute to their strength and durability.
Rocks based on their suitability can be used for foundation
for dams, tunnelling's and other construction materials.
Hence it is most important branch of Geology from civil
Engineering point of view.

Structural Geology
The rocks which forms the earth’s crust undergoes various
deformation, dislocations and disturbances under the
influence of tectonic plates forces.
The results is the occurrence of geological structures like
folds, faults, Joints and unconformities in the rocks.
The detailed mode of formation, causes, types, classification,
important etc.,

Structural Geology (FAULTS)

Structural Geology (FOLDS)

Structural Geology
Geological structures modified the inherent physical
characteristics of rock rendering them more suitable or
unsuitable for civil engineering purpose.
Dam site sedimentary rocks with upstream dip provided a
desirable geological setup while the same rock with down
stream dip make geological setup un desirable.

Historical Geology
The earth surface was always suitable condition for the
deposition of sediments at some place or other place. Therefore
there are sedimentary rocks on the earth representing the entire
period of the earth history. proper investigation of this rocks
reveals the chronological sequence of formation of rocks,
evolution ,migration and plants and animals life during different
period of the earth history. These kind of study of the earths
history through sedimentary rocks is called historical geology.

Palaeontology
If , under favourable condition, animals and plants life gets
embedded in sediments , it will be preserved partly or
completely .such remnants of ancient life preserved in rocks
by natural processes are known as Fossils.
Details of mode of formation of fossil their types, occurrence
etc form the subject matter of palaeontology. Its not much
important from civil engineering point of view.

Economic Geology
Minerals can be grouped into rock forming mineral and
economic minerals. some of the economic minerals like talc,
graphite, mica, asbestos, gypsum, magnetite and diamond
are useful as row materials in some industries.
Some others like hematite, chromite, galena and Pyrolusite
are used for ore extraction of various metals.

Economic Geology
The prosperity of a nation depends to a large extent of rich
reserves of economical minerals deposit.
Gulf countries are rich because of their oil deposit;
South Africa is rich because of its gold and diamond deposited.
It deals with the mode of formation, occurrence, classification,
association, varieties and concentration, properties and uses. etc
Its is related to economic importance.it is not related civil
engineering point t of view

Engineering Geology
This deals with the application of geological knowledge in
the field of civil engineering for execution of safe, stable and
economic construction like dams, bridges and tunnels.
23Engg- Geo [6K473]-Unit1

Mining Geology
This deals with the application of geological knowledge in
the field of mining.
A mining engineer is interested in the mode of extent of
occurrence of ores, their association, tenor, properties etc.,
It is also necessary to know other physical parameter like
depth, direction (strike), inclination (dip) thickness and ore
bodies.

Geo physics
The study of physical properties like density and magnetism
of earth. It is sub divided into Pure geophysics and
Exploration geophysics.
Pure geophysics deals with general aspects of earth as a
whole and Exploration geophysics deals with the study of
upper layer of the earths crust in order to solve civil
engineering problem and locating oil, gas and ground water
explore and estimate the ore deposit.

Pure geophysics

Exploration geophysics

Geo Hydrology
This may also called as Hydrogeology. It deals with
occurrence, movement and nature i.e., (quality and quantity)
of ground water in an area.
This branch is closely related to geology because the very
existence movement of ground water are directly related to
porosity , permeability, structure, texture and composition of
ground water and under ground rocks.

Geo Chemistry
This branch is relatively more recent and deals with
occurrence , distribution, abundance, mobility, etc., of
different elements on the earth crust. It is not important
from the civil engineering point of view.

Scope of Geology
 Geology provides necessary information about the
construction materials at the site used in the construction
of buildings, dams, tunnels, tanks, reservoirs, highways and
bridges.
 Geological information is most important in planning
stage, design phase and construction phase of an
engineering project.

Scope of Geology
 Geology is useful to know the method of mining of rock
and mineral deposits on earth’s surface and subsurface.
 Geology is useful for supply, storage and filling up of
reservoirs with water.
 This is the only subject which gives the information about
the earth surface.

Importance of Geology in Civil Engineering
 Before constructing roads, bridges, tunnels, tanks,
reservoirs and buildings, selection of site is important from
the point of stability of foundation.
 Geology provides a systematic knowledge of construction
materials and their properties.
 The knowledge about the nature of the rocks in tunnelling
and construction of roads.

 The foundation problems of dams, bridges and buildings are
directly related with geology of the area where they are to
be built.
 The knowledge of ground water is necessary in connection
with excavation works, water supply, irrigation and many
other purposes.

 The knowledge of Erosion, Transportation and Deposition (ETD)
by surface water helps in soil conservation, river control.
 Geological maps and sections help considerably in planning
many engineering projects.
 If the geological features like faults, joints, beds, folds are found,
they have to be suitably treated. Hence, the stability of the rock
structures is important.
 Pre-geological survey of the area concerned reduces the cost of
planning work.

General Geology
Any rocks which is hard and strong it may be decided when it
is exposed to the atmosphere, ultimately making the rock
unfit to be at the site of foundation or to be used as a
construction materials.
Details of response of different minerals which constitute the
rocks will give the proper understanding of the weathering
phenomenon. Hence the weathering of rocks is studied in
General Geology.

Geological Agents
The Natural forces which are responsible for the visible
changes on the earth surface are called Geological agents.
Based on their origin these natural forces can be grouped into
two types
 Exogenous Geological Agents
 Endogenous Geological Agents

Exogenous Geological Agents
The agents originated on the earth’s surface, work slowly but
steadily and erase topographic irregularities i.e., ups and
downs on the surface.
The geological work in a way is systematic, i.e.,
commencement with erosion and is followed by
transportation and deposition.

The erosion process causes the disappearance of land mass
like hills.
The deposition process causes the disappearance of
depressed land mass like pit, lakes and sea.
Rivers, wind glaciers, tides and waves of sea are typical
example of exogenous groups of agents.

Case study Example
 Himalayan rivers i.e., Ganga, Indus and Brahmaputra physically
transport 1 million tons of sediments daily.
 South west monsoon winds transport over 1,30,000tons of salts
particles annually from run of Kutch toward Rajasthan.
 Glaciers also do work of such magnitude even they are capable of
transporting huge boulders many meters in diameter.

In hills due to erosion, rocks are broken down into smaller
pieces, which are transported and deposited in the
depression

Endogenous Geological Agents
The nature, origin and function of endogenous
geological agents are in principal opposite to
exogenous geological agents. They originated below
the earth surface, work suddenly and create
topographic Irregularities.
Volcanoes, earthquakes, ground water and tectonics
forces are typical example.

Endogenous Geological Agents

Weathering of Rocks
The process by which rocks are broken down and
decomposed by action of external agencies such as
wind, rivers, rain, temperature, changes is called
Weathering.
Mechanical Weathering
Chemical Weathering
Biological Weathering

Weathering of Rocks
These process involves breakdown of rocks into smaller
pieces due to natural forces like waterfalls, landslides.
The different types of mechanical Weathering are
 Frost wedging
 Expansion and contraction
 Effects of vegetation

Weathering of Rocks
Frost wedging
The presence of water in the cracks of the rocks freezes
during the night time and melts during day time. Freezes of
water involves an increase in volume because of which walls
of crakes are wedged ultimately results in break down.

Weathering of Rocks
Frost wedging

Weathering of Rocks
Expansion and contraction process:
Solar radiation causes heating, which results in thermal
expansion during day time and drop in the temperature
during the night time causes contraction. The expansion and
contraction are confined only to the surface layers of the rock
and results in fracture.

Weathering of Rocks
Expansion and contraction

Weathering of Rocks
Effect of vegetation
During the growth of vegetation in rocky terrains, the roots
penetrate into the existing weak planes and gradually the
cracks are widened leading to physical breakdown of rock
masses.

Weathering of Rocks
Effect of vegetation

Weathering of Rocks
Chemical weathering
Chemical weathering involves chemical reactions resulting in
the alteration of the rock leading to the formation of new
alteration products. Water is the best fluid that directly
affects rocks by way of Dissolution; Leaching (making
porous); Hydration; Oxidation.

Weathering of Rocks
Chemical Weathering
Dissolution
In case of carbonate rocks such as limestone, dolomite,
marble when the river water traverses in these rocks;
carbonates are dissolved, resulting in the reduction of their
sizes.

Weathering of Rocks
Chemical Weathering
Dissolution

Weathering of Rocks
Chemical Weathering
Leaching
Leaching means removable of soluble content from the rocks
by water. Water is the powerful leaching agent which affects
leaching for the most of the materials when come in contact
with water.

Weathering of Rocks
Chemical Weathering
Leaching

Weathering of Rocks
Chemical Weathering
Hydration
Hydration is the process where in hydroxyl molecules are
injected into the molecular structures of minerals thereby
bringing about the decomposition of minerals.

Weathering of Rocks
Chemical Weathering
Hydration

Weathering of Rocks
It involves breakdown of rocks by living organisms like
Bacteria & fungi, Acid, Hemic acid etc.. which cause
decomposition of rocks. Some of the microorganisms
penetrate into mineral crystals and remove specific ions from
the intern layers.

Weathering of Rocks

Earth Structure
Atmosphere
The outer gaseous part of the Earth starting from the surface
and extending as far as 700 km and even beyond is termed
atmosphere.

Earth Structure
Atmosphere

Earth Structure
Troposphere
 It is the lowermost zone of the atmosphere rising from the
surface of the earth extending, on an average to a height of
20 km.
 Its upper boundary called tropopause about 9km above
the poles and at 18 km above the equator.

Earth Structure
Troposphere

Earth Structure
Stratosphere
 It is the second layer of the atmosphere starting from the
tropopause and extending up to an average height of 50 km.
 The temperature becomes constant for a height of 20km
(above tropopause) and then starts increasing.
 The Ozone Layer starts at a height of 9 km above the
surface and continues up to 35 km.

Earth Structure
Stratosphere

Earth Structure
Mesosphere
 This is the third thermal zone of atmosphere which begins
at stratopause at about 50km above the surface and
continues up to a height of about 85 km.
 It is characterized with a steep fall in temperature that may
go to as low levels as—100 °C at the upper limit of
mesosphere.

Earth Structure
Mesosphere

Earth Structure
Thermosphere
 The fourth and the last zone of the atmosphere starts at
about 85 km and extends up to 690 km.
 In this zone, temperature starts rising once again and
reaches 1000°C and above.
 Atmospheric gases at these heights absorb a great part of
solar radiation coming to the Earth.

Earth Structure
Exosphere

Earth Interior Structure

Earth Structure
Lithosphere
 The term lithosphere is now understood to include only the
uppermost shell of the earth, the crust and a part of the
second layer, the mantle, up to which the material exists in
a definite solid state.
 CRUST
 UPPER MANTLE

Earth Structure
Crust
It is the uppermost solid shell of the
earth which has varying thickness in
different areas as follows
(a) Under the oceans 5 - 6 km
(b) Under the continents 30 - 35 km
(c) Under the mountains : 60 - 70 km

Earth Structure
 Oceanic Crust
◦ crust beneath the oceans
◦ consist mainly of dense rock (basalt - dark in color)
◦ 5-6 km thick
 Continental Crust
◦ crust that forms the continents
◦ consist mainly of less dense rock (granite - lighter in color)
◦ 35 km average thickness

Mantle (60-2900)
 layer of rock between crust and core
2900km thick, 67% of Earth’s mass
 Composition - silicon, oxygen, iron and
magnesium
 physical conditions in mantle change
because pressure and temperature increase
with depth.
◦ temp ranges from 870 ºC to 2,200ºC

Core
 Innermost layer of the Earth
 6800 km in diameter (3,500 km from outside edge of core
to center of core)
 1/3 of Earth’s mass, 15% of its volume
 Temperature ranges from 2,000 ºC to 7,000ºC
Consist of 2 parts; Inner Core and Outer Core

Outer Core (2900-5000)km
 layer of molten (Liquid) metal (iron and
nickel) beneath the mantle
 surrounds the inner core 2,200 km thick.
Inner core (5000-6370)km
 dense ball of solid metal (iron and nickel)
 extreme pressure from layers above 1200
km, from outside edge of inner core to center

Tectonic Plates
 Plate tectonics states that the Earth's crust and upper mantle are
broken into sections, called Tectonic plates.
 These plates move around the mantle.
 Plates are composed of the crust and a part of the upper mantle,
these two parts together are called the lithosphere.
 The layer below the lithosphere is the asthenosphere.
 The lithosphere floats or moves around on the asthenosphere.

Tectonic Plates

Tectonic Plates
Conventional Current
Large convection
currents in the
asthenosphere transfer
heat to the surface,
where plumes of less
dense magma break
apart the plates at the
spreading centres,
creating divergent plate
boundaries.

Types of Plate Boundaries
How does continental drift work.
Plates collide = convergent boundary.
Plates separate = divergent boundary.
Plates slide past one
another horizontally = transform boundary.
Seductions zone = one plate slides under another.

When both are
continental plates, the
plates push against
each other, creating
mountain ranges.

1. Andes Mountains of
South America formed
at the convergent
boundary of
the Nazca and the
South American
plates.

2.Himalayan
Mountains in Asia
were formed when
the Indo-Australian
Plate collided with the
Eurasian Plate.

Plates separate = divergent boundary
As the plates are
pulled apart, magma
is extracted from the
mantle to fill in the
void. The magma
cools and records the
magnetic field
characteristics. New
crust is formed at
Divergent Boundaries.

North American plate
moving away from the
Eurasian and the
African plates causing
the Mid Atlantic ridge.

Great Rift Valley in eastern Africa

Plates slide past one another = transform boundary.
Transform margins are
conservative in the sense
that along these margins
material is translated, not
created or destroyed.
Faulting along transform
margins is strike-slip.

The San Andreas Fault
is a transform fault
boundary and has
been the site of
many earthquakes.

Introduction of Engineering Geology

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