Uses and types of rocks (geology) along with faults found in rocks. Practical examples and demonstration of measuring dip strike in the field.

1. Presented By
Things Simplified
( A New Perspective )

2. 
Utilisation of Rocks
The rocks are utilised in construction industry majorly, in two ways:
 Rocks with which construction is done
 Used as ballast for supporting the sleepers.
 Used as coarse and fine aggregates for preparation of concrete
 Used on the exterior face of the building or structure for aesthetics as well
as protection purpose.
 Used in base, sub-base and top of roads and runways
 Rocks over which construction is carried on
 Supports heavy and huge structures such as dams, weirs, multi-storey
buildings.
 Construction of tunnels and shafts.

3. 
Classification of Rocks
The rocks can be classified on the basis of the following:-
 Origin and Genesis
 Geological or lithological classifications
 Engineering Classification of Intact Rocks
 A combination of these

4. 
Classification of Rocks
(Cont.)
Based on origin and genesis the rocks are of three types:-
 Igneous Rocks
 Sedimentary Rocks
 Metamorphic Rocks

5. 
Igneous Rocks
 Rocks that are formed by cooling of molten magma either on the surface of
earth or deep inside the crust.
 Extrusive or Volcanic- Molten magma when thrown out of the volcano on
earth’s surface and it cools down rapidly forming fine grained rocks called
extrusive igneous rocks.
 Hypabyssal- Molten magma when cools down in-between crust (below 2
km from earth’s surface).
 Intrusive or Plutonic- Molten magma inside earth (in-between core and
mantle) when comes upto level of the crust it cools down but not as fast as
extrusive rocks as molten magma is deep inside earth crust and not on
surface. Slow coolings leads to formation of coarse grained rocks called
intrusive rocks.

6. 
Extrusive Igneous Rocks
Examples:- Andesite, Basalt, Dacite, Obsidian, Pumice, Rhyolite, Scoria, And Tuff.
Basalt

7. 
Hypabyssal Igneous
Rocks
Examples:- Diabase, Quartz-dolerite, Micro-granite And Diorite.
Diabase

8. 
Intrusive Igneous Rocks
Examples:- Gabbro, Granite, Pegmatite, And Peridotite.
Granite

9. 
Sedimentary Rocks
Rocks that are formed by weathering or decomposition of the earth’s crust or any
existing rock form. Based upon the agents causing sedimentary deposition,
sedimentary rocks are classified as:-
 Mechanically
 Organically
 Chemically

10. 
Mechanically Deposited
 The deposition caused by rivers, glaciers, winds, etc.
 Examples:- Breccia, Conglomerate, Sandstone, Siltstone and Shale
Sandstone

11. 
Organically Deposited
 Sediments derived from the remains of animals and plants.
 Examples:- Coal, some Dolomites, and some Limestones.
Coal

12. 
Chemically Deposited
 Formation of sediments due to chemical decomposition.
 Examples:- Rock Salt, Iron Ore, Chert, Flint
Rock Salt

13. 
Metamorphic Rocks
The effects of high temperatures and high pressures on igneous or sedimentary
rocks results in recrystallization of them into new form called metamorphic rocks.
The agents that cause metamorphism to take place are:-
 Temperature
 Pressure
 Stress
 Chemically Reactive Substances

14. 
Metamorphic Rocks
(Cont.)
 Examples:- Marble, Genesis, Schist.
 The widely used metamorphic rock is marble which is formed when
metamorphism takes place on limestone.
Marble

15. 
Lithological
Classification
The study of physical characteristics of rocks is called lithology. The physical
characteristics are sub-divided as following:-
 Texture
 Structure
 Composition
 Color
 Grain Size

16. 
Texture
The rocks are sub-divided into following textural groups: -
 Crystalline : Inter-locking of grains are visible with naked eye. When scratched
with knife or blade particle grains doesn’t come out.
 Indurated : Inter-locking of grains which are not visible with naked eye. When
scratched with knife or blade particle grains doesn’t come out.
 Crystalline-Indurated : The texture of grains of this type of rocks lies between
crystalline and indurated texture. The texture is more finer than crystalline but
less finer than indurated. When scratched, grains doesn’t come out.
 Compact : The grains are held together by tight packing. The rock has finer
texture. The material comes out when scratched with knife or blade.
 Cemented : The texture of grains belongs to medium to coarse grained
material. The grains are tied together with the help of cementious material.
The grains comes out if scratched with finger nail or knife.

17. 
Structure
The structure of the rocks based on lithological study can be further classified into
following: -
 Homogeneous – Grains are having random orientation.
 Lineated – If mineral particles are oriented in a particular fashion in a linear
direction. These are aelotropic or non- isotropic rocks.
 Intact-Foliated – When particles are having particular orientation in a plane.
 Fracture-Foliated – Planer structure having cleavage planes.

18. 
Composition
Based on composition of rocks, they are classified as:
 Non-Calcareous : The rocks materials doesn’t having calcium carbonate.
 Part-Calcareous : The materials consisting of mainly non-calcareous material.
The calcareous material is present for creating bond between grains.
 Calcareous : The rocks material containing calcite.

19. 
Colour
The colour of the rocks are divided into two parts: -
 Light Coloured – The rocks that have acidic nature.
 Dark Coloured – The rocks that have basic nature.
Calcareous rocks containing impurities are dark in nature whereas pure calcareous
rocks are light in colour.

20. 
Grain Size
The grain size of different rocks are categorized into three types: -
 Coarse Grained – When particle size is larger than 2 mm.
 Medium Grained – When particle size of grain is between 2 mm and 0.1 mm.
 Fine Grained – When particle size is less than 0.1 mm. Particles of such size are
invisible to eyes.

21. 
Classification Based on
weathering
Term Description Grade
Fresh No visible alga of material weathering. IA
Faintly
Weathered
Discolouration on major discontinuity surfaces. IB
Slightly
Weathered
Discolouration indicates weathering of rock material and discontinuity of surfaces. All the
rock material may be discoloured by weathering and may be somewhat weaker than its
fresh condition.
II
Moderately
Weathered
Less than half the rock material is decomposed and/or disintegrated to a soil. Fresh or
discoloured rock is present either as a discontinuous framework or as core stones.
III
Highly
Weatherd
More than half the rock material is decomposed and/or disintegrated to soil. Fresh or
discoloured rale is present either as a discontinuous framework or as core stones
IV
Completely
Weathered
All rock material is decomposed and/or disintegrated to soil. The original mass structure is
largely intact.
V
Residual
Soil
All rock material is converted to soil. The mass structure and material fabric are destroyed.
There is a large change in volume but, the soil has not been significantly transported.
VI

22. 
Classification of Rocks –
Based on Uniaxial Strength
Class Description
Uniaxial Compressive
Strength (kg/cm2)
Rock Material
A Very High Strength Over 2250
Quartzite, diabase, basalts. Majority of
igneous rocks. Strong metamorphic
rocks.
B High Strength 1125-2250
Weakly cemented sand stones, hard
shales, majority of lime stones, dolomites.
C Medium Strength 562.5-1125
Many shales, porous sandstones, and
lime-stones, schistose varieties of
metamorphic rocks.
D Low Strength 281.25-562.5
Porous low-densityrocks, friable sand-
stone, truff.
E Very low Strength Less than 281.25
Clay shales, weathered and chemically
altered rocks of any lithology.

23. 
Classification of rocks –
Based on Modulus of
Elasticity
Class Description Modulus Ratio
H High More than 500
M Medium 200-500
L Low Less than 200

24. 
Defects In Rocks
It is important to study about the defects that are there in rocks as from engineering
point of view the foundations of the structure are to rest on rocks and if the rocks have
some defect then the stresses that are to be transferred to the rock mass may not be
evenly distributed.
The weakness in the rocks is due to the presence discontinuities in them.

25. 
Defects in Rocks (Cont.)
The different types of discontinuities found in rocks are: -
 Fractures
 Cracks
 Fissures
 Bedding Planes and Laminations
 Stratifications
 Joints
 Faults
 Folds and Cavities

26. 
Causes of Defects in
Rocks
There are mainly two root causes for the occurrence of defects in rocks. They are
as follows: -
 Epeirogenic or continent building movements – The defects caused due to the
movements of ocean floor or continents. These movements are very slow.
 Orgenic or mountain building movements – The defects caused by the
movements occurring in the mountains. These are very disturbing forces and
occurs periodically. They result in the formation of complex formation of rocks.

27. 
Strike and Dip
Strike
Dip

28. 
Joints
Cracks along which the fractured rocks masses doesn’t appear to have moved
relatively to each other are called joints.
Types of Joints are:-
 Flat laying joints
 Q joints or cross joints
 S joints or longitudinal joints

29. 
Faults
When there is relative displacement taking place at the plane of the fracture then
that plane is termed as fault. The displacement may be vertical or horizontal.
Types of faults:
 Normal Fault
 Reverse Fault

30. 
Faults (cont.)
Normal Fault
Reverse Fault

31. 
Folds
The wavy undulations developed in the rocks due to high stresses are called folds.
Different modes of folds are: -
 Concentric Folding
 Cleavage
 Flow

32. 
Folds (cont.)
Concentric
Cleavage

33. 
Rock Quality
Designation
Nowadays, RQD or Rock Quality Designation is an important parameter adopted by the
engineers worldwide to know the quality of the in-situ rock.
It is defined as the ratio of total length of core recovered to the length of drilling done.

35. 
Rock Quality Designation
(cont.)
R.Q.D. (Rock Quality
Designation) in %
Rock Quality Description
0-25 Very Poor
25-50 Poor
50-75 Fair
75-90 Good
90-100 Excellent

36. Any Query, ask
in
comments

37. Thanks for your
Attention
Have a Nice Day

38. 
 Types of Rocks
https://www.youtube.com/watch?v=IALC36xRjew
 Dip Strike
https://www.youtube.com/watch?v=FbXhooadhZw
 Folds
https://www.youtube.com/watch?v=rjn2ZJwpqQA
https://www.youtube.com/watch?v=rEumMkAhwzA
 RQD – Rock Quality Designation
https://www.youtube.com/watch?v=dOZwwhn60aY
Video References