This document provides an overview of geotechnical engineering and soil mechanics. It covers the origin of soils from weathering rocks, the formation of sedimentary, residual, and fill soils, and the structure of soil particles. It also discusses alterations to soil properties over time due to stress, water, and other environmental factors. The document is presented as part of a soil mechanics assignment from a geotechnical engineering course with sections on the contents, origin of soil, soil formation, soil structure, and alterations. It provides definitions and descriptions of key soil mechanics concepts.

1. GEOTECHNICA
L
ENGINEERING
ASSIGNMENT ON SOIL
MECHANICS
GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCUTRE
ALTERATIONS

2. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
SOIL
STRUCTURE
3
SOIL
FORMATION
2
ORIGIN
OF SOIL
1
• TYPES OF
ROCKS
• WEATHERING
OF ROCKS
• SEDIMENTARY
SOIL
• RESIDUAL
SOIL
• FILL
How soils are the
results of
geological events?
How soil is
formed?
THE
ORIENTATION
AND
DISTRIBUTION OF
PARTICLES IN A
SOIL MASS.
What is the
structure of soil?

3. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
 Soils are the results of geological events (except
for the very small amount produced by man). The
nature and structure of a given soil depends on
the geological processes that formed it:
- breakdown of parent rock: weathering,
decomposition, erosion.
- transportation to site of final deposition: gravity,
flowing water, ice, wind.
- environment of final deposition: flood plain, river
terrace, glacial, marine.
- subsequent conditions of loading and drainage -
little or no surcharge, heavy surcharge due to ice
or overlying deposits, change from saline to
freshwater, leaching, contamination.
ORIGIN OF SOIL

4. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
All soils originate, directly or indirectly, from solid
rocks in the Earth's crust:
1. Igneous rocks
crystalline bodies of cooled magma e.g. granite,
basalt, dolerite, gabbro, syenite, porphyry
2. Sedimentary rocks
layers of consolidated and cemented sediments,
mostly formed in bodies of water (seas, lakes, etc.)
e.g. limestone, sandstones, mudstone, shale,
conglomerate
3. Metamorphic rocks
formed by the alteration of existing rocks due to
heat from igneous intrusions (e.g. marble,
quartzite, hornfels) or pressure due to crustal
movement (e.g. slate, schist, gneiss).
TYPES OF PARENT
ROCKS

5. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
1. Physical weathering
Physical or mechanical processes taking place on the
Earth's surface, including the actions of water, frost,
temperature changes, wind and ice; cause
disintegration and wearing. The products are mainly
coarse soils (silts, sands and gravels). Physical
weathering produces Very Coarse soils and Gravels
consisting of broken rock particles, but Sands and
Silts will be mainly consists of mineral grains.
2. Chemical weathering
Chemical weathering occurs in wet and warm
conditions and consists of degradation by
decomposition and/or alteration. The results of
chemical weathering are generally fine soils with
separate mineral grains, such as Clays and Clay-Silts.
The type of clay mineral depends on the parent rock
and on local drainage. Some minerals, such as quartz,
WEATHERING OF ROCKS

6. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
SEDIMENTARY SOIL
Other mineral soils develop
from small particles coming
from mineral soils
developed in another
location, transported for
some distance, and
deposited. These are called
sedimentary soils.
RESIDUAL SOIL FILL
03
02
01
Residual soil is defined as a
soil material which is derived
from rock bedding and has
not undergone
transportation, usually found
in tropical climates with
relatively high temperatures
and rainfall.
Soil used for filling,
that is, found within
or
contemporaneously
placed within a
cavity, or a supply
of soil for use
as fill.

7. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
1. Sedimentary Soil:
The individual particles were created at one location, transported,
and finally deposited at another location.
• Sediment Formation: the formation of sediment is by the
physical and chemical weathering of rocks on the surface of
the earth. Generally silt, sand, and gravel sized particles are
formed by the physical weathering of rocks and clay-sized
particles are formed by the chemical weathering of rocks.
• Sediment Transportation: sediments can be transported by any
of five agents (they are water, air, ice, gravity, and organisms).
The effects of transportation on sediments are Alters particle
shape, size, and texture by abrasion, grinding, impact,
solution.
Sorts the particles.
• Sediment Deposition: the particles are deposited to form
sedimentary soil. The causes of deposition in water are: -
 velocity reduction, solubility decrease, and electrolyte
increase.
SOIL
FORMATION

8. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
2. Residual Soil:
◦ Residual soil results when the
products of rocks weathering are not
transported as sediments but
accumulate in place. If the rate of rock
decomposition exceeds the rate of
removal of the products of
decomposition, an accumulation of
residual soil results.
◦ The factors influencing the rate of
weathering are: climatic (like
temperature and rainfall), time, type of
source rock, vegetation, drainage, and
bacterial activity.

9. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
3. Fill:
◦Fill is man-made soil deposit. A fill is actually a
“sedimentary” deposit for which man carried out
all of the formation processes.
◦The fill soil can be left as dumped (such as rock
toe in the earth dam), or can be processed and
densified – compacted – as for the core in the
earth dam.
◦Borrow Soil: is the soil obtained from a source
or made by blasting, transported by land vehicle
(such as truck, scraper, pan or bulldozer) or
water vehicle (barge) or pipe, and then
deposited by dumping.

10. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
Soil will be picked
up by the crane
from a particular
soil field
SOIL FIELD
Then the picked
up soil will be
emptied in a
truck
LOADING
Then the soil
carrying truck will
be unloaded at the
construction site.
UNLOADING
FILL TRANSPORTATION

11. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STURCTURES
ALTERATIONS
• Soil Structure refers to the orientation and distribution of
particles in a soil mass (also called “fabric” and “architecture”)
and the forces between adjacent soil particles.
• This is limited to small, plate shaped particles, and to the
orientation of individual particles. This includes bedding
orientation, stratification, layer thickness, the occurrence of
joints and fissures, the occurrence of voids, artifacts, tree
roots and nodules, the presence of cementing or bonding
agents between grains.
• Structural features can have a major influence on in situ
properties.
o Vertical and horizontal permeability will be different in
alternating layers of fine and coarse soils. A
o The presence of fissures affects some aspects of strength.
o The presence of layers or lenses of different stiffness can
affect stability.
o The presence of cementing or bonding influences strength
SOIL STRUCTURE

12. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STURCTURES
ALTERATIONS
• Cohesive
matrix
structure
• Honeycomb
structure
• Coarse
grained
Skelton
structure
• Dispersed
structure
• Single grained
structure
• Flocculated
structure
SOIL STURCTURES
Here we will see some grained structures, sheetlike
structures, and composite structures.

13. GTE-1
CONTENTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIONS
ALTERATIONS OF SOIL AFTER
FORMATION
 The civil engineer working with soil must
design his structure not only for the
properties of the soil as it exists at the
start of the project but also for the entire
design life of the structure. He needs to
know both the properties of the soil at the
start of the project and how these
properties will vary during the design life.
 The factors influencing the changes in soil
behavior are: stress, time, water, and
environment.

14. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
DESCRIPTION OF THE
INDIVIDUAL SOIL PARTICLE
COMPOSITION OF
SOIL PARTICLES
APPEARANCE OF A
SOIL PARTICLE
PARTICLE SIZE
SHAPE OF
GRAINS
DEGREE OF
ROUNDNESS,
TEXTURE, AND
COLOR
FORCES ON SOIL
PARTICLE
DESCRIPTION OF THE INDIVIDUAL SOIL
PARTICLE

15. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
The nature and arrangement of the
atoms in a soil particle is called “soil
composition”. The composition have a
significant influence on permeability,
compressibility, strength, and stress
transmission in soils, especially in
fine-grained soils. There are three
main groups of clay minerals:
DESCRIPTION OF THE INDIVIDUAL SOIL
PARTICLE
COMPOSITION OF SOIL
PARTICLES

16. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
DESCRIPTION OF THE INDIVIDUAL SOIL
PARTICLE
APPEARANCE OF A SOIL PARTICLE
1. PARTICLE SIZE:
Particle size depends on the dimension
that was recorded and how it was
obtained. Two ways of determining
particle size are: -
• sieve analysis for particle longer than
(0.06) mm.
• hydrometer analysis for smaller
particles.

17. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
Very coarse
soils
BOULDERS > 200 mm
COBBLES 60 - 200 mm
Coarse
soils
GRAVEL
Coarse 20 - 60 mm
Medium 6 - 20 mm
Fine 2 - 6 mm
SAND
Coarse 0.6 - 2.0 mm
Medium 0.2 - 0.6 mm
Fine 0.06 - 0.2 mm
Fine
soils
SILT
Coarse 0.02 - 0.06 mm
Medium
0.006 - 0.02
mm
Fine
0.002 - 0.006
mm
CLAY < 0.002 mm
APPEARANCE OF A SOIL PARTICLE
Table shows different sizes of soil.

18. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
APPEARANCE OF A SOIL PARTICLE
2. SHAPE OF GRAINS:
The majority of soils may be regarded as: -
• Equidimensional: The particle size could be given by
single number only as a cube or sphere. This situation
for soil particles in the silt range and coarser.
• Sheetlike: As in clay size particles
• Rounded: Water- or air-worn; transported sediments.
• Irregular: Irregular shape with round edges; glacial
sediments (sometimes sub-divided into 'sub-rounded'
and 'sub-angular’)
• Angular: Flat faces and sharp edges; residual soils,
grits
• Flaky: Thickness small compared to length/breadth;
clays
• Elongated: Length larger than breadth/thickness;
broken flagstone
• Flaky & Elongated: Length>Breadth>Thickness; broken
schists and slates

19. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
APPEARANCE OF A SOIL PARTICLE
2. SHAPE OF GRAINS:

20. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
 The degree of roundness refers to the
sharpness of the edges and corners of a
particle.
 Surface texture is minor feature of surface of a
particle, independent of size, shape, or degree
of roundness. The terms used to describe
surface texture are dull or polished, smooth
or rough, striated, frosted, etched, or pitted.
APPEARANCE OF A SOIL PARTICLE

21. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
 Color is a useful particle characteristics to the geologist
working in mining, but it is of little value to the soil engineer.
The colors and their indications in the followings: -
◦ Red color: due to the presence of non-hydrated Fe2O3.
◦ Clear yellow and brown colors: indicates good drainage.
◦ Bluish grey colors: reduced or bivalent iron compounds.
◦ Black and dark brown colors: are characteristic of organic
matter.
colors: due to preponderance of silica, lime, gypsum,
and relatively pure clay deposits.
APPEARANCE OF A SOIL PARTICLE
4. COLOUR

22. GTE-1
CONETNTS
ORIGIN
OF
SOIL
SOIL
FORMATION
SOIL
STRUCTURE
ALTERATIO
NS
• Specific surface is the ratio of surface area per unit
weight.
• Surface forces are proportional to surface area (i.e. to
d²).
• Self-weight forces are proportional to volume (i.e. to
d³).
Mineral/Soil
Grain width,
d (mm)
Thickne
ss
Specific Surface,
m²/N
Quartz grain 100 d 0.0023
Quartz sand 2.0 - 0.06 »d 0.0001 - 0.004
Kaolinite 2.0 - 0.3 »0.2d 2
Illite 2.0 - 0.2 »0.1d 8
Montmorilloni
te
1.0 - 0.01 »0.01d 80
APPEARANCE OF A SOIL PARTICLE

23. DISCOVERY
DISCOVERY:
According to Terzaghi (1948):
“Soil Mechanics is the
application of laws of mechanics
and hydraulics to engineering
problems dealing with
sediments and other
unconsolidated accumulations of
solid particles produced by the
mechanical and chemical
disintegration of rocks
regardless of whether or not
they contain anadmixture of
organic constituent.

24. TEAM
TEAM MEMBERS
1 SNEHA PAI
USN: 1BM20CV164
2 TUSHAR LAKHOTIA
USN: 1BM20CV178
5 SRI RAM SHARMA
USN: 1BM20CV168
4 ZEESHAN MOHAMMED
USN: 1BM20CV191
3 TANMAY KANKARIYA
USN: 1BM20CV173
B.M.S. COLLEGE OF ENGINEERING, BENGALURU
(Autonomous Institute Affiliated to VTU)
Department of Civil Engineering

25. TEAM
B.M.S. COLLEGE OF ENGINEERING, BENGALURU
(Autonomous Institute Affiliated to VTU)
THANK YOU.