diploma in civil engineering · any chemical change. the smaller broken rock pieces are deposited...

SY CIVIL Fourth Sem

Sanjay Ghodawat Polytechnic, Atigre 1

Key Points to Remember:

Second Year

Diploma in Civil Engineering

Fourth Semester

C h a p t e r w i s e N o t e s

GEO TECHNICAL ENGINEERING

SY CIVIL Fourth Sem



Subject Title: Geo Technical Engineering Subject Code : 17420

Topic 1: General geology, mineralogy and petrology. (08 Marks)

Contents:

• Introduction of geology, different branches of geology, importance of geology for civil

engineering structure and composition of earth. Introduction to mineralogy, physical

properties of minerals depending on light and state of aggregation.

• Introduction of petrology, definition of a rock, classification based on their genesis

(mode of origin), formation, classification and engineering uses of igneous, sedimentary

and metamorphic rocks.

Que.1 Define petrology and mineralogy.

Ans: i. Petrology: Formation of various types of rocks, their mode of

occurrence, composition, texture and structures, geological and

geographical distribution on the earth are all studied under

petrology. It is one of the important subdivisions of geology and is

further subdivided into distinct branches: Igneous petrography,

Sedimentary petrology and metamorphic petrology.

ii. Mineralogy: Mineralogy is that branch of geology, which deals

with formation, occurrence, aggregation, properties, and uses of

minerals. Mineralogy sometimes itself divided into specific sub-

branches such as crystallography, optical mineralogy and

descriptive mineralogy and so on.

Que.2 State and briefly explain any four physical properties of minerals.

ANS: Minerals have distinguishing physical properties that in most cases

can be use to determine the identity of the mineral. Among the

various properties crystal, habit, cleavage, hardness, density, luster,

streak color, tenacity, magnetism and taste.

Individual Crystals:

i) Cubic: cube shapes

ii) Octahedral: shaped likes octahedrons,

iii) Tabular: rectangular shapes examples – feldspar

SY CIVIL Fourth Sem



iv) Equant: a term used to describe minerals that have all of

boundaries of approximately equal length.

v) Acicular: long slender needle like crystals, example – natrolite

vi) Prismatic: Abundance of prism faces

vii) Bladed: like a wedge or knife blade example – kyanite

Cleavage: Crystals often contain planes of atoms along which the

bonding between the atoms is weaker than along other planes.

Parting: parting is also a plane of weakness in the crystal structure

but it is along planes that are weakened by some applied force.

Fracture: If the mineral contains no planes of weakness it will break

along random directions called fracture several different kinds of

fracture patterns are observed:

i) Conchoidal fracture ii) Fabrous and splintery

iii) Hackly iv) Even or regular

v) Uneven or Irregular

Hardness: hardness is determined by scratching the mineral with a

mineral or substance of known hardness.

Tenacity: Tenacity is the resistance of a mineral to breaking,

crushing, or bending.

i) Brittle: breaks or powder

ii) Malleable : can be hammered into thin sheet

iii) Sectile: can be cut into thin sheeting with knife.

iv) Ductile: bends easily and does not return to its original

shapes.

v) Flexible: bend s somewhat and does not return to its original

shape.

vi) Elastic: bends but does return to its original shape.

Specific Gravity (Density): It is the mass per unit volume. It is also the

relative density (weight of substance divided by the weight of an

equal volume of water)

Colour: color is sometimes an extremely diagnostic property of

mineral.

SY CIVIL Fourth Sem



Que.3 What is meant by geologic cycle? State the types of weathering

and explain brief.

Ans: Geologic cycle: The most important of these begins with molten

magma from within the earth crystallizing into rock then continues

with the rock being broken down into soil and that soil then being

converted back into rock, This process repeats itself over and over

again through geologic time.

Types of weathering:

i) Mechanical weathering

ii) Chemical weathering

iii) Spheroidal weathering

iv) Biological weathering

Mechanical weathering: It is also termed as physical weathering in

this process the rock surface is broken into smaller pieces without

any chemical change. The smaller broken rock pieces are

deposited at and over the present rock on the flat surface and

these are accumulated at the end of slopping surface. It is slow

process with water and temperature.

Chemical weathering: In this process the rock surface is broken into

small pieces by chemical decay of minerals. It is chemical reaction

between the atmospheric gases and surface of rock weathering

are oxidation, hydration, carbonation and solution.

Spheroidal weathering: If joints and fractures in rock beneath the

surface form a 3-dimentional network the rock will be broken into

cube like pieces separated by fracture water can penetrate more

easily along these fracture and each of the cube like begin to

weather inward.

Biological weathering : Plants and animals play an important role in

the break down and decay of rock indeed their part in soil

formation is of major significance.

SY CIVIL Fourth Sem



Que.4 Define geology and state any one importance in Civil Engineering.

Ans: Geology: is the science that deals with the study of the earth as a

planet. Thus, it includes essence of scientific studies dealing with the

origin, age and structure of the earth.

1. It is used to study different properties of rocks.

2. For any heavy construction project study of geology is required.

Que.5 State classification of rocks based on their genesis :

Ans: Rock: - Aggregation of minerals is called rock or minerals occurring

in natural aggregated form called rock.

i. Igneous rock

ii. Sedimentary

iii. Rock

iv. Metamorphic rock

Que.6 Enlist any four physical properties of minerals.

Ans: Following are the four physical properties of minerals

i) Colour ii) Luster iii) Streak

iv) Hardness v) Cleavage vi) Fracture

vii) Tenacity viii) Structure (form) ix) Specific gravity

x) Miscellaneous-Magnetic, Electrical.

Que.7 State objectives of Geotechnical Engineering.

Ans: Following are the objectives of geotechnical engineering:

1) To perform soil investigation and to develop methods for soil

sampling.

2) To classify soil properties in the light of soil engineering product.

3) To apply the result and soil investigation and sampling, so as to

use soil as construction material economically

SY CIVIL Fourth Sem



Topic 2: Structural Geology (8 Marks)

Contents:

• Structural Geology: Definition, importance, Outcrop, dip, strike, folds- Definition, parts

and types, Joints- Definition and classification, Faults- Definition, parts and Types

Que.1 State importance of structural geology.

Ans: importance of structural geology

Geology provides a systematic knowledge of

construction materials, their structure and properties.

The knowledge of erosion, transportation and

deposition of surface water helps in soil conservation,

river control, coastal and harbor works.

The knowledge about the nature of the rocks is very

necessary in tunneling, constructing roads and in

determining the stability of cuts and slopes.

The foundation problems of dams, bridges and

buildings are directly related with geology of the area

where they are to be built.

Que.2 State the field application of Geotechnical Engineering.

Ans: Following are field application of Geotechnical Engineering

a. In foundation design

b. In pavement design

c. In earth retaining structures

d. In design of earthen dams

e. In design of embankments

f. In design of under ground structures

Que.3 Define outcrop and strike.

Ans: i. Out crop: The dip and strike of beds can be easily

measured in the field from their exposures called outcrops.

ii. Strike: The horizontal distance perpendicular to the fault

plane is called as strike.

SY CIVIL Fourth Sem



Que.4 Define Faults and state any two types of it.

Ans: Define Fault : The fractures along which there has been relative

movements of the blocks past each other are termed as faults.

Types of Fault: - a) Normal Fault b) Reverse Fault.

Que.5 Define a) Out Crop b) Dip c) Strike d) Fold.

Ans: a) Outcrop: - The dip and strike of beds can be easily measured in

the field from their exposures called outcrops

b) Dip: - Dip is an angle between the horizontal plane and the

inclined plane measured perpendicular to the direction of strike.

c) Strike: - The horizontal distance perpendicular to the fault plane

is called as strike.

d) Folds: - Folds may be defined as undulations or bends that are

developed in the rock of the Earth’s crust, as a result of stresses

(commonly lateral compression) to which these rock have been

subjected to, from time to time in the past history of the Earth.

Que.6 Define fault and state its classification

Ans: Fault – It is defined as the rupture / fracture along which there is a

relative movement of beds. The movement may vary from few

centimeters to many km. depending upon nature and magnitude

of stresses and resistance offered by rock.

Classification of fault :

1) Based on position of fault plane.

(a) Normal Fault

(b) Reverse Fault

2) Based on their genesis

a) Gravity fault

b) Thrust fault

c) Strike / slip fault

2) Horst and Graben

3) Step fault

4) Bedding fault

5) Dip fault

6) Strike fault

SY CIVIL Fourth Sem



Que.7 Define joints and state their classification.

Ans: Joints: joint are defined as a fracture in rock where there has been

no lateral movement in the plane of the fracture (up, down or

sideway) of one side relative to the other.

Classification of joints:

a) Spatial joints

i) Systematic joints (regular joints)

ii) Non- systematic (irregular) joint

b) Geometry

i) strike joints, ii) Dip joints, iii) Oblique joints.

c) Origin

i) Tension joints, ii) Shear joints, iii) Compression joints

Que.8 Define a fault and state its classification.

Ans: Fault: The fractures along which there has been relative movement

of the blocks past each other.

The entire process of development of fractures and displacement

of the blocks against each other is termed as faulting.

Following factors are more considered important in classification of

faults:

a. The apparent movement of the disrupted blocks along the fault

plane.

b. The direction of slip.

c. The relation of fault attitude with the attitude of the attitude of

the displaced beds.

d. The amount of dip of the fault.

e. Mode of occurrence.

The apparent movement of the disrupted blocks along the fault

plane in two types

i) Normal faults: Such a fault in which hanging wall has apparently

moved down with respect to foot wall classified as a normal fault.

SY CIVIL Fourth Sem



Normal faults are also often termed as gravity faults especially

when it is established that the hanging wall has actually moved

down with respect to the foot wall.

ii) Reversed faults: It is a type of fault in which the hanging wall

appears to have moved up with respect to the foot wall. In

reversed faults the fault plane is generally inclined between

horizontal and 450 although reversed faults with steeply inclined

fault surface have been also encountered by virtue of their

inclination and direction of movement reverse faulting involves

shortening of the earth.

iii) Strike- slip faults: This is the third major category of faults known

to occur in nature and on a very large scale these may be defined

as faults in which faulted blocks have been moved against each

other in an essentially horizontal direction.

SY CIVIL Fourth Sem



iv) Hinge faults: These are also called pivotal faults or rotational

faults a hinge fault is characterized by a movement of the

disrupted blocks along a medical poit called the hinge point.

Que.9 What is a fold and state its types ?

Ans: Fold: It is defined as undulations or curvatures developed in the

rocks of the crust as a result of stresses to which these rocks have

been subjected from time to time in the past history of the earth.

Folds generally do not occur singularly but infact they often form a

group in which individual members exibit many similarities as well as

dissimilarities

Deception Figure

i) Anticlinorium: An anticlinorium fold

is a large anticline which is further

throw into smaller fold

ii) Synclinorium: Syclinorium is a large

syncline further consisting of smaller

folds are very large in size

iii) Domes and Basins: A dome is a

special type of anticline in which the

beds dip away from the central

point in all directions.

SY CIVIL Fourth Sem



iv) A Basin is a special type of

syncline in which the beds dip

towards central point from all

directions. In outline, domes and

basins are generally oval or nearly

circular in shape

v) Anticlines: Beds are up folded into

arch like structure.

vi) Sydine: Beds are down folded

into a trough like structure.

vii) Overturned folds: Both the limbs

of afold may get overturned

because of very high compression

viii) Fan fold: limbs dipping away

from each other

ix) Recumbent Folds: One limb lies

vertically above the other.

SY CIVIL Fourth Sem



x) Isoclina Folds: These folds may be

vertical, inclined or horizontal are

called as vertical isoclinal fold,

Inclined isoclinal fold, recumbent

isoclinal fold.

xi) Open fold and Closed fold:

Thickness of bed is same throughout

the layer are called as open fold

and thickness is more at trough and

crest at the limbs is called closed

fold.

Que.10 Draw neat sketch of 1) Recambent fold 2) Overturned fold

1) Recambent fold

2) Overturned fold

SY CIVIL Fourth Sem



For Details contact:

Mr. V.S. kumbhar

HOD

Civil Department,

Sanjay Ghodawat Polytechnic, Atigre.

Mob. No.: 7798306363

Ph. No.: 0230 -246312

Email ID: [email protected]

mailto:[email protected]

diploma in civil engineering · any chemical change. the smaller broken rock pieces are deposited...

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