Engineering Soil Mechanics (Fawzan Fahry)

Classify and Analyze the properties of soils
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1.1 Examine Modes Of Formation, Engineering Descriptions
and Classification Of Common Rock Types.
Rocks.
Rock is the hard and durable material.
Rock’s defined as the solid material forming the outer rocky shell or crust of
the earth.
Naturally- occurring mixtures of minerals, mineralogist, glass or organic
matter.
There are three major groups of rocks by its origin
 IGNEOUS
 SEDIMENTARY
 METAMORPHIC
 IGNEOUS
Rocks formed by the cooling and solidifying of molten materials.
Igneous rocks can form beneath the Earth's surface, or at its surface,
as lava.
 Extrusive igneous rock is formed from lava (on earth’s surface)
and tends to solidify quickly.
 Ex: Andesite Basalt, Obsidian, Pumice, Rhyolite and
Scoria
 Intrusive igneous rock is formed from magma (inside the earth)
and tends to take a long time to solidify into rock.
 Ex: Diorite, Gabbro, Granite and Pegmatite

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Above ground = from lava (extrusive igneous rock).
Usually have SMALL or NO crystals (they cooled too
quickly)
Igneous Rock Formation.
 Extrusive igneous rock.
Igneous rocks are called fire rocks and are
formed either underground or above ground.
Underground, they are formed when magma deep
within the Earth becomes trapped in small pockets.
As these pockets of magma cool slowly they
become igneous rocks. Igneous rocks are also
formed when volcanoes erupt. Igneous rocks are
formed as the lava cools above ground. The upper
16 km of the Earth’s crust is composed of 95%
igneous rock.
 Intrusive igneous rock.
Intrusive igneous rocks are formed
from magma that cools and solidifies underground.
These rocks are coarse grained. The mineral grains
in such rocks can generally be identified with the
unaided eye. They can be classified according to the shape and size of
the intrusive body and its relation to the other formations into which it

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intrudes. Intrusive formations are batholiths, stocks, laccoliths, sills, and
dikes.
 SEDIMENTARY
Sedimentary rock is a rock formed near Earth’s surface
from pieces of other rocks, plant or animal
remains, or by the build-up of chemical
solids.
All types of rock are continuously being
broken down into small fragments
called sediment.
This sediment can be compressed or
cemented together to form sedimentary
rock.
Sedimentary Rocks formed by the
deposition of material at the Earth's
surface and within bodies of water.
Sedimentation is the collective name for
processes that cause mineral and/or
organic particles (detritus) to settle and
accumulate or minerals to precipitate
from a solution.
There are three basic types
of sedimentary rocks.
1. clastic sedimentary rocks
Formed from mechanical weathering debris
 Ex: Breccia, Conglomerate, Sandstone and Shale
2. chemical sedimentary rocks
Form when dissolved materials precipitate from
solution
 Ex: salt and some limestone
3. organic sedimentary rock
Form from the accumulation of plant or animal
debris.
 Ex: coal and some limestone

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Sedimentary Rock Formation.
As the sediments become buried under other sediment
layers, pressures and temperatures increase. The sediment hardens into a
sedimentary rock, or lithifies, after it has gone through the stages of
compaction, dewatering, and cementation. During compaction, the grains of
sediment are packed more tightly together. With increasing pressure some of
the water between the sediment particles is squeezed out, dewatering the
sediment. This process reduces the pore space, or open spaces between the
grains. At this point, pressure and temperature conditions are such that certain
minerals, usually calcite or quartz, fill some or all of the pore spaces and
adhere to the sediment fragments, cementing them into a sedimentary rock.
Formed from sediments (rock fragments, mineral grains, animal & plant
remains) that are pressed or cemented together or when sediments precipitate
out of a solution.
• Compaction: is when pieces of sediment are squeezed together by the
weight of overlying layers (including water)
• Cementation of sediment occurs when minerals are deposited in a bed
of sediment and as the water evaporates the dissolved minerals form
crystals that “glue” the sediment particles to each other.
• These sediments are moved by wind, water, ice or
gravity.
• Sedimentary rocks represent 7% of the Earth’s crust, but
they cover 70% of the Earth’s surface.
• Sedimentary rocks are fossil-carrying rocks.

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 METAMORPHIC
Metamorphic rock is a rock formed by the transformation of existing
rock, as a result of extreme heat and or pressure.
Rocks that have changed due to intense temperature and pressure
“Meta” means “change” and morphosis means “form” in Greek
Igneous, sedimentary and other metamorphic rocks can change to
become metamorphic rocks
There are two
basic types of metamorphic rocks.
1 Foliated metamorphic rocks.
Layered or banded appearance that
is produced by exposure to heat and
directed pressure.
Mineral grains are flattened and line
up in parallel bands.
 Ex: Gneiss, phyletic, Schist and Slat
2 Non-foliated metamorphic rocks.
No bands are formed.
 Ex: Marbles.
 Formation Of Metamorphic Rocks .
Schist rocks are metamorphic.
These rocks can be formed from basalt, an
igneous rock shale, a sedimentary rock or
slate, a metamorphic rock. Through
tremendous heat and pressure, these rocks were transformed into this
new kind of rock.
Gneiss rocks are metamorphic.
These rocks may have been granite, which is an igneous rock, but heat
and pressure changed it. You can see how the mineral grains in the rock
were flattened through tremendous heat and pressure and are arranged
in alternating patterns.

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1.2 Describe The Common Rock Forming Minerals and Their
Susceptibility to Weathering.
Minerals and rocks
Rock is natural, solid, nonliving material made of one or more minerals.
Mineral is natural, nonliving material that makes up rock.
Rocks get their properties from the minerals they contain.
The properties of rocks include color and texture.
 Grains are bits of minerals. They are big enough to see them.
 Texture is the size and pattern of a rock`s grains.
Properties to Minerals
 Color
 Luster
 Streak
 Cleaving & Fracture
 Hardness
 Density
 Special Properties
 Color
 Usually the first and most easily observed
-Some minerals are always the same color
-Some minerals can have many colors
ROSE QUARTZ QUARTZ SMOKY QUARTZ

7The intrinsic color of the mineral.
 NOTE: color is rarely diagnostic - usually a very poor
Some examples...
 Sulfur is normally yellow.
 Pyrite is normally brassy.
 Quartz can have almost any color
 Luster
 General appearance of a mineral surface in reflected light
 Example: Dull or Shiny
 Types of Luster:
o Metallic/Glassy (Shiny)
o Submetallic (Dull)
o Nonmetallic (Dull)
METALLIC: opaque, looks like a metal such as gold,
 METALLIC
Opaque, looks like a metal such as gold,
silver, iron, etc.
 NON-METALLIC:
(needs to be more descriptive)
– VITREOUS or GLASSY (Samples 3, 12) - strong glint (shiny like
glass)
– PEARLY (talc, some gypsum) - looks like mother-of-pearl
– RESINOUS - reflects light in a manner similar to syrup or tree sap
("glazed")
– EARTHY- dull, little or no reflection

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 Streak
The color of a finely powdered mineral
Determined by rubbing the mineral on a piece of unglazed porcelain (streak
plate)
More reliable than Color because weathering doesn’t change the Streak Color
The streak (also called "powder color") of a mineral is the color of the powder
produced when it is dragged across an
un weathered surface.
 Cleaving & Fracture
Minerals break in certain ways depending on how the atoms are
arranged
o Cleaving: When minerals break along flat surfaces
 Ex. Diamonds and Rubies
o Fracture: When minerals break unevenly or irregularly
 Ex. Quartz

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1) Talc
2) Gypsum
3) Calcite
4) Fluorite
5) Apatite
6) Feldspar
7) Quartz
8) Topaz
9) Corundum
10) Diamond
 Hardness
Hardness refers to a mineral’s resistance to being scratched
Example: Diamond is the hardest mineral
Mohr’s Hardness Scale:
Scale 1 – 10 Reference Minerals – p. 66
 Density
Density is how much matter there is in a given amount of space
Density of Water: 1 g/cm3
Specific Gravity = Object’s Density/Density of Water
The specific gravity of an unknown mineral .
 Special Properties
Some minerals have unique properties:
Taste (ex. Halite)
Fluorescence (ex. Calcite & Fluorite)
Chemical Reaction (ex. Calcite)
Optical Properties (ex. Calcite)
Radioactivity (ex. Radium & Uranium can be detected in a mineral)
Magnetism (ex. Magnetite)
Softest
Hardest
1
2
3
4
5
6
7
8
10
9

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Common rock-forming minerals
Along with the common rock-forming minerals, we have included apatite,
corundum, diamond, fluorite, topaz and talc to illustrate minerals used in Mosh
Scale of Hardness.
1. Apatite
Apatite is a phosphate mineral . The name actually covers
three different minerals (Fluor apatite, color apatite and hydroxyl
apatite) depending on the predominance of either fluorine, chlorine or
the hydroxyl group. These ions can freely substitute in the crystal lattice
and all three are usually present in every specimen, although some
specimens have close to 100% in one or other. The three are usually
considered together due to the difficulty in distinguishing them in hand
samples using ordinary methods.
Apatite is widely distributed in all rock
types (igneous, sedimentary and metamorphic), but usually as
small disseminated grains, or cryptocrystalline fragments. Large,
well-formed crystals can be found in certain contact metamorphic rocks.
Chemical composition Ca5(PO4)3(OH, F,
Cl)
Hardness – 5
Specific gravity - 3.1-3.2
Transparency - Transparent to translucent
Color - Typically green but also yellow, blue,
reddish brown and purple
Streak – White
Luster - Vitreous to greasy
Cleavage/fracture - Poor / conchoidal
Crystal habit/mode of occurrence - Prismatic
(hexagonal prism with hexagonal pyramid
orpinacoid or both as
termination), acicular /granular, massive
2. Augite
Augite is a member of the pyroxene group of simple silicates, in
which the SiO4 tetrahedral are linked by sharing two of their four

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corners to form continuous chains. For this reason they are often
referred to as single chain silicates.
Pyroxenes are subdivided into those with
orthorhombic symmetry (orthopyroxenes), and those with monoclinic
symmetry (clinopyroxenes), with augite being the most common of the
clinopyroxenes.
Augite is commonly found in igneous rocks such
as gabbros, basalts and andesite’s, and high grade metamorphic rocks
(granulites).
Chemical composition - (Ca, Na)(Mg, Fe, Al)(Al,
Si)2 O6
Hardness - 5-6
Transparency - Transparent to mostly translucent
or opaque
color - Dark green, brown and black
Streak - Greenish white
Luster - Vitreous
Cleavage/fracture - Imperfect in two lengthwise
directions at close to right angles / uneven
(distinctive square cross section), tabular /granular
3. Biotitic
Biotite is a member of the mica group of silicates (sheet silicates),
like chlorite and muscovite. It occurs in more geological environments
than any of the other micas. It is a common rock forming mineral, being
present in at least some percentage in many igneous rocks
( granite and rhyolite), and metamorphic rocks (schist, gneiss).
Chemical composition - K(Fe, Mg)3AlSi3O10
(F, OH)2
Hardness - 2.5-3
color - Brown to black
Streak - Very pale brown
Luster - Vitreous to pearly
Cleavage/fracture - Perfect in one direction
producing thin sheets or flakes / uneven

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Crystal habit/mode of occurrence - Tabular (sheets or flakes) / granular
4. Calcite
Calcite is the only common non-silicate rock forming mineral,
being instead calcium carbonate. It has two refractive indices causing a
significant double refraction effect - when a clear calcite crystal is placed
on an image, a double image is observed; See the sample below.
Calcite will fizz when dilute hydrochloric acid is placed on it.
It may be fluorescent, phosphorescent; thermo luminescent and tri
bioluminescent (see fluorite for definitions of these properties).
Calcite is one of the most ubiquitous minerals, being an
important rock forming mineral in sedimentary environments. It is an
essential component of limestone’s, and occurs in other
sedimentary rocks. It also occurs in metamorphic and igneous rocks,
and is common in hydrothermal environments. Calcite is a common vein
filling mineral in many rock types.
Chemical composition - CaCO3
Hardness - 3
Specific gravity - 2.7
color - Generally white or colorless, but also with
light shades of yellow, orange, blue, pink, red,
brown, green, black and grey
Streak - White
Luster - Vitreous to resinous
Cleavage/fracture - Perfect in three directions at
oblique angles / conchoidal
(rhombohedra crystals)
5. Chlorite
Chlorite is a member of the mica group of minerals (sheet
silicates), like biotite and muscovite.

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Chlorite is widespread in low grade metamorphic rocks
such as slate and schist, in sedimentary rocks, and as a weathering
product of any rocks that are low in silica (especially igneous rocks).
Chemical composition - (Fe, Mg, Al)6(Si,
Al)4O10(OH)8
Hardness - 2-2.5
Transparency - Translucent to transparent
color - Generally green (various shades)
Streak - Pale green
Luster - Vitreous, pearly
Cleavage/fracture - Perfect / uneven
Crystal habit/mode of occurrence -
Tabular(rarely large individual barrel or
tabular crystals with a hexagonal outline) /
fine-grained, scaly or massive aggregates of
small scales
6. Corundum
is the second hardest natural mineral known to science (1/4 the
hardness of diamond). Gem varieties are sapphire and ruby.
Corundum may occur on a large scale in some pegmatites. It is also found in
silica-poorhornfelses (a contact metamorphic rock).

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Chemical composition - Al2O3
Hardness - 9
Specific gravity - 4+
color - Highly variable - white or color less,
blue, red, yellow, green, brown, purple, pink
Streak - White
Luster - Vitreous to adamantine
Cleavage/fracture - Non-existent / conchoidal
(six-sided barrel shape that may taper into a
pyramid, hexagonal prisms and blades)
/ massive, granular (called emery)
7. Diamond
is the hardest naturally occurring mineral, topping Mohs' Scale of
Hardness with a relative hardness value of 10.
Diamond is a polymorph of the element carbon, and graphite is another. While
the two share the same chemistry, C (elemental carbon), they have very
different structures and properties. Diamond is hard, graphite is soft (the
"lead" of a pencil). Diamond is an excellent electrical insulator, graphite is a
good conductor of electricity. Diamond is the ultimate abrasive (its most
important use), graphite is a very good lubricant. Diamond is transparent,
graphite is opaque. Diamond crystallizes in the isometric system, graphite
crystallizes in the hexagonal system. However, at surface temperatures and
pressures graphite is the stable form of carbon. In fact, all diamonds at or near
the surface of the Earth are currently undergoing a transformation into
graphite, although this reaction is extremely slow.

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Facts about diamond:
 Diamond is transparent over a larger range of wavelengths than any
other substance, from the ultra-violet into the far infra-red.
 Diamond conducts heat better than any substance - five times better
than the next best element, silver.
 Diamond has the highest melting point of any substance (3820 degrees
Kelvin).
 Diamond's atoms are packed closer together than the atoms of any other
substance.
Diamond is only formed at high pressures. It is found in kimberlitic, an
ultrabasic volcanic rock formed very deep in the Earth's crust. The extreme
pressures needed to form diamonds are only reached at depths greater than
150km.
Chemical composition - C
Hardness - 10
Transparency - Transparent to translucent in rough
crystals
color - Variable, tends toward pale yellows, browns,
greys, and also white, blue, black, reddish, greenish
and colorless
Streak - White
Luster - Adamantine to greasy
Cleavage/fracture - Perfect in 4 directions forming
octahedrons / conchoidal
(isometric forms such as cubes and octahedrons)
8. Fluorite
is frequently fluorescent, it will glow under ultra-violet
light. This occurs because certain electrons in the mineral absorb the
energy from the ultra-violet light and jump to a higher energy state. The
fluorescent light is emitted when those electrons jump down to a lower
energy state and emit a light of their own.
Rare examples of fluorite may exhibit phosphorescence, i.e. they will
continue to glow when removed from the ultra-violet light source. This
occurs because electrons in the mineral have stored energy from the
ultra-violet light which they then emit on a delayed basis.

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Rare examples of fluorite may exhibit thermo luminescence,
they will glow when heated. This occurs because the mineral may
contain chemical bonds that emit light when thermal energy (heat) is
applied.
An even rarer property sometimes exhibited by fluorite is
triboluminescence, where minerals glow when they are crushed, struck,
scratched or even rubbed in some cases. The minerals contain chemical
bonds that emit light when mechanical energy is applied to them.
Fluorite is a common vein mineral associated with mineral deposits.
Chemical composition - CaF2
Hardness - 4
Transparency - Transparent to
translucent
color - White if pure, but extremely
variable - purple, blue, green, yellow,
colorless, reddish orange, pink, white,
brown; a single crystal can be multi-
coloured
Streak - White
Luster - Vitreous
Cleavage/fracture - Perfect in 4
directions forming octahedrons
/ hackly
Prismatic, always equant (typically
cubes and to a lesser extent
octahedrons as well as combinations
of the two) / less common are crusts
and botryoidalforms

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Garnet
is a more complex orthosilicate (than olivine, for example) in
which the SiO4tetrahedra are still independent. Garnet is commonly found in
highly metamorphosed rocks and in some igneous rocks. They form under the
same high temperatures and / or pressures that form those types of rocks.
Garnets can be used by geologists to gauge the temperature and pressure
under which a particular garnet-bearing rock formed.
Chemical composition - Fe3Al2Si3O12(almandine)
Hardness - 6.5-7.5
Transparency - Transparent to opaque
color - Variable - most commonly red, reddish
brown
Streak - White
Luster - Vitreous to resinous
Crystal habit/mode of occurrence - Prismatic (12-
sided rhombic, 24-sided trapezoidal)
/granular, massive
9. Gypsum
has a very low thermal conductivity (hence its use as an
insulating filler). A crystal of gypsum will feel noticeably warmer than,
for instance, a crystal of quartz.
Gypsum is one of the more common minerals in sedimentary
environments. It is a major rock forming mineral that produces massive
beds, usually from precipitation out of highly saline waters.

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Chemical composition - CaSO4-2(H2O)
Hardness - 2
color - Usually white, colorless or grey, also shades
of red, brown and yellow
Streak - White
Luster - Vitreous to pearly (especially on cleavage
surfaces)
Cleavage/fracture - Perfect in one direction,
imperfect in two others / uneven (rarely seen)
Hornblende
is a member of the amphibole group of more complex silicates, in
which the tetrahedral are linked to form a continuous chain twice the
width of the pyroxene chains. For this reason they are often referred to
as double chain silicates. Like the pyroxenes, they can be subdivided
into those with orthorhombic symmetry and those with monoclinic
symmetry . Hornblende is the most common of the clinoamphiboles.
Hornblende is commonly found in metamorphic rocks such
as schist’s and gneisses, and igneous rocks such as diorites and decides.

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Chemical composition - Ca2(Mg, Fe, Al)5(Al,
Si)8O22(OH)2
Hardness - 5-6
Transparency - Opaque
color - Dark green to black
Streak - Dark green
Luster - Vitreous
Cleavage/fracture - Imperfect in two directions at
56° and 124° / uneven
Prismatic,acicular, fibrous / massive, granular
10. Ilmenite
is the most important ore of titanium. It is similar in appearance
to magnetite, but has a different crystal form and if it is magnetic then
it's not as strongly so as magnetite. It will become magnetic when
heated.
Ilmenite is a common accessory mineral in many igneous rocks and also
found as a detrital mineral (in sands).
Chemical composition - FeTiO3
Hardness - 5-6
Specific gravity - 4.5-5
color - Black
Streak - Black
Luster - Metallic
Tabular (thin and thick tabular crystals with
rhombohedra truncations, sometimes formed
into rosettes) /massive and granular, as grains
in some sands

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Magnetite
is a natural magnet, hence its name. This is a distinguishing
characteristic of the mineral. Magnetite is a common accessory mineral
in igneous rocks and is also found as a detrital mineral, particularly on
the beaches west of Auckland (black sand).
.
Chemical composition - Fe3O4
Hardness - 5.5-6.5
color - Black
Streak - Black
Luster - Metallic
(typically octahedral but rarely rhomb dodecahedral)
/ massive, granular
11. Muscovite
is a member of the mica group of silicate minerals (sheet
silicates) in which the base of all of the SiO4 tetrahedral lie in one plane
and three corners of the base are shared with the neighboring
tetrahedral. This creates a strongly layered sheet-like structure, hence
the term sheet silicate (the sheets are weakly bound together by layers
of potassium ions). Muscovite, biotite and chlorite are all common mica
group minerals.

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Muscovite is commonly found in metamorphic rocks such
as schist’s and gneisses, sedimentary rocks (as the fine grained variety
sericite), and in igneous rocks such as granite.
Although muscovite has perfect cleavage, individual sheets are
quite durable and are often found in sands that have undergone erosion
and transport that would have destroyed most other minerals. Sheets of
muscovite have high heat and electrical insulating properties and are
used in the manufacture of many electrical components. Muscovite
sheets were used for kitchen oven windows before synthetic materials
replaced them.
Chemical composition -
KAl3Si3O10(OH)2
Hardness - 2-2.5
Transparency - Transparent to
translucent
color - White, silver, yellow, green
and brown
Streak - White
Luster - Vitreous to pearly
Cleavage/fracture - Perfect in one
direction producing thin sheets or
flakes / uneven
Crystal habit/mode of
occurrence - Tabular (sheets or
flakes)
12. Olivine
is a simple orthosilicate in which the SiO4 tetrahedral are
independent of each other. It is a solid solution of the end-members
forsterite (Mg2SiO4) and fayalite (Fe2SiO4), although most examples are
closer to the forsterite end-member.

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Olivine is very susceptible to alteration and often has a brownish
weathering rind of assorted clay minerals.
Olivine is most commonly found in igneous rocks of low silica content,
such as basalts and gabbros, and is occasionally found
in metamorphic rocks.
Chemical composition - (Mg, Fe)2SiO4
Hardness - 6.5-7
color - Yellowish green to green, also colorless,
greenish brown to black
Streak - White
Luster - Vitreous
Cleavage/fracture - Imperfect / conchoidal
(equant to elongate) / granular, massive
13. Orthoclase
is a member of the feldspar group (like plagioclase)
and is a framework silicate. Orthoclase, also known as alkali feldspar or
K-feldspar, is one end-member of a solid solution between orthoclase
and albeit. Orthoclase is found in silica-rich igneous rocks such
as granite, and in high grade metamorphic rocks.
14. Plagioclase
is a member of the feldspar group (like orthoclase) and is a
framework silicate. Plagioclase consists of a solid solution between the
albite and anorthite end-members, and together with quartz is the most
common of the rock forming minerals.
Chemical composition - KAlSi3O8
Hardness - 6
Transparency - Translucent to opaque (rarely
transparent)
color - Pinkish white, off-white, yellow, or shades of
red, orange to brown
Streak - White
Luster - Vitreous
Cleavage/fracture - Perfect in two directions, seldom
twinned / hackly, conchoidal

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The twinning in plagioclase produces stacks of twin layers
that are typically fractions to several mm thick. These twinned layers
can be seen as striation like grooves on the surface of the crystal and,
unlike true striations, these also appear on cleavage surfaces.
Plagioclase is found in almost all igneous rocks and
most metamorphic rocks, but is less common in sedimentary rocks
where it usually weathers to clay minerals or a fine grained variant
of muscovite (sericite).
Chemical composition - CaAl2Si2O8 (anorthite),
NaAlSi3O8 (albite)
Hardness - 6-6.5
Transparency - Translucent to opaque (rarely
transparent)
color - Usually white, grey or colorless
Streak - White
Luster - Vitreous
Cleavage/fracture - Perfect in two directions,
commonly twinned / hackly, conchoidal
Crystal habit/mode of occurrence - Prismatic,
tabular
15. Pyrite
also known as "Fool's Gold" because of its brassy-yellow metallic colour,
is the most common sulphide mineral in rocks of all ages, being found in
virtually every geological environment. It is easily distinguishable from
gold as it has a lower specific gravity. Pyrite is a common component of
sedimentary rocks and metamorphosed sediments, is an accessory
mineral in many igneous rocks, and forms large bodies in hydrothermal
deposits.

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Chemical composition - FeS2
Hardness - 6-6.5
color - Brassy yellow
Streak - Greenish black
Luster - Metallic
Cleavage/fracture - Non-existent / hackly,
conchoidal
(cube, octahedron and pyritohedron [a
dodecahedron with pentagonal faces])
/ massive, granular
Quartz
is a complex silicate in which all the oxygen atoms of the
SiO4 tetrahedral are shared between two tetrahedral, leading to complex
3-dimensional frameworks. For this reason, quartz is referred to as a
framework silicate.
Quartz is among the most common of all rock forming
minerals and is found in many metamorphic rocks, sedimentary rocks,
and those igneous rocks that are high in silica content such
as granites and rhyolites. It is a common vein mineral and is often
associated with mineral deposits.
Cryptocrystalline varieties are used as semi-precious
stones and for ornamental purposes. These varieties are divided more
by character than by color. Chalcedony, or agate, is divided into
innumerable types that have been named for locally common varieties.
Some of the more beautiful types have retained their names while other
names have faded into obscurity. Some of the more common are
chrysoprase (a pure green agate), sard (a yellow to brown agate),
sardonyx (banded sard), onyx (black and white agate), carnelian (a
yellow to orange agate), flint (a colourful and microscopically fibrous
form), jasper (a colourful impure agate) and bloodstone (a green with
red speckled agate).

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Chemical composition - SiO2
Hardness - 7
color - Clear is most common (pure quartz),
also white or cloudy (milky quartz); but can
be very variable - purple (amethyst), pink
(rose quartz), grey or brown to black (smoky
quartz) are also common; yellow to orange
(citrine) are more rare; cryptocrystalline
varieties can be multicolored
Streak - White
Luster - Vitreous
Cleavage/fracture - Non-existent
/ conchoidal
Prismatic (hexagonal prism terminated with
a six sided pyramid)
/ cryptocrystalline, massive
Talc
is the softest mineral, demonstrated by its position at the
bottom of Mohs' Scale of Hardness with a relative hardness value of 1. It
has a soapy, greasy feel.
Talc is formed by the hydrothermal alteration of ultrabasic rocks, or low
grade thermal metamorphism of siliceous dolomites.
Most people know talc as the primary ingredient in talcum powder.
However, talc is an important industrial mineral. Its resistance to heat,
electricity and acids make it useful for lab counter tops and electrical
switchboards. It is important filler in paints, rubber and insecticides.
Talc often replaces other minerals atom by atom to form pseudo
morphs, taking the form of the replaced mineral. Thus, a specimen of
what appears to be milky quartz would actually be talc, having a soapy
feel and being able to be scratched with a fingernail.

26
.
Chemical composition -
Mg3Si4O10(OH)2
Hardness - 1
Transparency - Crystals translucent,
masses opaque
color - Green, grey and white to almost
silver
Streak - White
Luster - Pearly, greasy
direction / uneven
Tabular (thin flakes, never large
crystals) / granular, cryptocrystalline
Topaz
is a common gem stone. Topaz crystals can reach very large sizes,
with crystals in pegmatites occasionally measuring several meters long
and weighing several hundred kilograms.
Topaz occurs mainly in felsic igneous rocks such as granite,
granite pegmatite and rhyolite, and is often found in veins and cavities
in such rocks.

27
Chemical composition - Al 2{SiO4}(OH, F)2
Hardness - 8
color - Colorless, pale yellow to amber; also
pale shades of blue, green, orange, red
Streak - White
Luster - Vitreous
direction /conchoidal
Prismatic (with a variety of terminal
pyramids andpinacoids)
/ massive, granular
Google. 2015. Google. [ONLINE] Available
at:https://www.google.lk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-
8#q=common%20rock%20forming%20minarals%20slide%20shere..
1.3 Evaluate The Common Usage Of Rock and Un- Cemented
Sediments For Construction.
Application of rocks to construction.
Rocks normally consist of several minerals, some essential, and
some accessory. A rock may be thought of as a "mineral environment." Each
rock type was formed under certain specific conditions, resulting in the
formation of a fairly predictable group of minerals. Rocks fall into three classes
according to their origin: Igneous - Sedimentary - Metamorphic
There are huge variations within each of these rock types,
caused by specific mineralogy and geology conditions, and while any
stone can be used for building, they each have constraints that make
them more or less suitable for different purposes.
 Granite, sandstone and limestone can all be used for building walls,
but slate is only suitable for roofs and floors.
Some types of granite can contain mineral salts that cause
spalling, where the outer face of stone falls off slate can contain harmful
minerals that break down on exposure to the atmosphere causing stone

28
damage. and sandstone can be too porous and fragile for load-bearing
structures.
LIMESTONE: A sedimentary rock, it is used mainly in the manufacture of
Portland cement.
SHALE: A sedimentary rock, well stratified in thin beds. It splits unevenly
more or less parallel to bedding plane and may contain fossils. It can be a
component of bricks and cement.
CONGLOMERATE: A sedimentary rock with a variable hardness, consisted of
rounded or angular rock or mineral fragments cemented by silica, lime, iron
oxide, etc. Usually found in mostly thick, crudely stratified layers. Used in the
construction industry.
SANDSTONE: A sedimentary rock more or less rounded. Generally thick-
bedded, varicolored, rough feel due to uneven surface produced by breaking
around the grains. Used principally for construction, it is easy to work, the red-
brown sandstone of Triassic age, better known as "brownstone," has been
used in many eastern cities.
GRANITE: An igneous-plutonic rock, medium to coarse-grained that is high in
silica, potassium, sodium and quartz but low in calcium, iron and magnesium.
It is widely used for architectural construction, ornamental stone and
monuments.
PUMICE: An igneous-volcanic rock, it is a porous, brittle variety of rhyolite and
is light enough to float. It is formed when magma of granite composition erupts
at the earth’s surface or intrudes the crust at shallow depths. It is used as an
abrasive material in hand soaps, emery boards, etc.
GABBRO: An igneous-plutonic rock, generally massive, but may exhibit a
layered structure produced by successive layers of different mineral
composition. It is widely used as crushed stone for concrete aggregate, road
metal, railroad ballast, etc. Smaller quantities are cut and polished for
dimension stone (called black granite).
BASALT: An igneous volcanic rock, dark gray to black, it is the volcanic
equivalent of plutonic gabbro and is rich in ferromagnesian minerals. Basalt
can be used in aggregate.
SCHIST: A metamorphic uneven-granular, medium to coarse grained,
crystalline with prominent parallel mineral orientation. Goes from silvery
white to all shades of gray with yellow to brown tones depending on the

29
mineral concentration. Some schist’s have graphite and some are used as
building stones.
GNEISS: A metamorphic uneven granular medium to coarse grained
crystalline with more or less parallel mineral orientation. Colors are too
variable to be of diagnostic value. Due to physical and chemical similarity
between many gneisses and plutonic igneous rocks some are used as building
stones and other structural purposes.
QUARTZITE: A metamorphic or sedimentary rock with crystalline texture,
consists of rounded quartz grains cemented by crystalline quartz, generally
white, light gray or yellow to brown. Same uses as sandstone.
MARBLE: A metamorphic even-granular grain to medium grained and may be
uneven granular and coarse grained in calk-silicate rock. The normal color is
white but accessory minerals act as coloring agents and may produce a variety
of colors. Depending upon its purity, texture, color and marbled pattern it is
quarried for use as dimension stone for statuary, architectural and ornamental
purposes. Dolomite rich marble may be a source for magnesium and is used as
an ingredient in the manufacture of refracting materials.
8#safe=active&q=common+usage+of+rocks+in+construction. .

30
Snapshot of geologic,
climatic,
Biological, and human
history
2.1 Produce Soil Description For In – Situ and Sampled
Materials.
Soil.
The upper layer of earth in which plants grow, a black or dark brown
material typically consisting of a mixture of organic remains, clay, and rock
particles.
Soil is the thin layer of loose mixture of small rock particles and rotting organic
matter that covers much of the world’s land surface.
 Soil is made up of mineral grains.
 Water is held between the grains in the pore
spaces.
 25% of the soil is air. Oxygen is essential
 Organic matter is both coarse and fine.
Soil Important.
Waste decomposer
Source material for
construction,
medicine, art, etc.
Filter of water and
wastes
Essential natural resource
Home to organisms
(plants, animals and others)
Medium for plant
growth
Producer and
absorber of gases
Medium of crop
production
Great integrator

31
Purpose Of Soil Classification.
Classifying soils into Groups With similar behavior in terms of simple indices
can provide geotechnical engineers general guidance about engineering
properties of the soil through the accommodated experience.
(Priodeep Chowdhury;Lecturer;Dept. of CEE;Uttara University// Origin of USCS )
2.2 Classify Solis.
Soil Classification System
 Particle Size Classification.
 Textural classification.
 Highway research Board classification. (HRB)
 Unified soil Classification System.
 Indian standard Classification System.
1. Describe the soil according to the British Soil Classification
System.
L.L = 45% PL = 18%
Plastic Index = LL – PL
= 45% - 18%
= 27%
Plastic Index = 27% Liquid Limit = 45%
Under the British Soil classification system we can identify this soil type.
This soil type is (ci ) - Clay Intermediate Soil.

32
2. Calculate The Activity Of The Soil.
Activity Of The Soil = PI
% Of Clay Particle.
= 27
24.2
= 1.12
3. Determine the Liquidity Index When its Natural
Moisture Content is 29%
Liquidity Index = M - PL
PI
= 29 - 18
27
= 0.4074
2.3 Determine Basic Soil Properties.
 Physical Properties Of Soil.
1. Color
The color of a soil can give clues to its
 Health
 Origin
 Long term changes.
It can also indicate the color of the parent material.
2. Texture

33
Texture refers to the relative proportion of sand , slit and clay in a
soil. It is one of the greatest factors in categorizing the types of soil.
3. Water Holding capacity
Soil’s capacity to hold water.
Micro pores - water is held in these small pore spaces in the form
of films adhering to the soil particles. This water is what the roots
can tap into and extract for plan use.
4. Permeability
Authorization of the soil to let substances pass through.
Macro pores - They do not hold water well because the water films
become too thick to adhere well to the surrounding soil particles.
This allows water and air to freely pass through.
 WATER CONTENT OR MOISTURE CONTENT
The water content is defined as the ratio of mass of water to
the mass of soils.
Water content = (weight of water / weight of dry soil) 100%
 BULK UNIT WEIGHT
Bulk unit weight is defined as the total weight of soil mass per
unit of total volume.
Bulk unit weight =
(total weight of soil mass / total volume of soil mass)100 %
 DRY UNIT WEIGHT
Dry unit weight is defined as the weight of soil solids per unit
of total volume of the soil mass.

34
Dry unit weight = (total weight of soil solids / total volume
of soil mass) 100%
 SATURATED UNIT WEIGHT
When soil mass is saturated, its bulk unit weight is called the
saturated unit weight.
Saturated unit weight = ( total weight of saturated soil
mass / total volume of soil mass )
 SUBMERGED UNIT WEIGHT
Submerged unit weight is defined as the ratio of submerged
weight of soil solids to the total volume of the soil mass.
Submerged unit weight = (submerged weight of soil solids
/ total volume of soil mass)
 SPECIFIC GRAVITY
Specific gravity is defined as the ratio of the weight of a given
volume of soil solids to the weight of an equal volume of
distilled water.
Specific gravity = (weight of a given volume of soil solid /
weight of an equal volume of distilled water)

35
 VOID RATIO
It is defined as the ratio of the volume of voids to the volume
of solids.
Void ratio = (volume of voids / volume of solids)
 POROSITY(n)
It is defined as the ratio of volume of voids to the total volume.
Porosity = (volume of voids/ total volume)
 DEGREE OF SATURATION
It is defined as the ratio of the volume of water to the volume of voids.
 Degree of saturation = ( volume of water / volume of voids)
In case of fully saturated soil, voids are completely filled with water.
There is no air.
 S r = 1
In case of fully dry soil, voids are completely filled with air.
There is no water
 AIR CONTENT
It is defined as the ratio of the volume of air to the volume of voids.
Air content = (volume of air/ volume of voids)
 PERCENTAGE AIR VOIDS
It is defined as the ratio of the volume of air to the total
volume.
Percentage air voids = (volume of air/ total volume )
It is represented as a percentage

36
 BULK DENSITY (b)
The bulk density is defined as the total mass per unit volume.
b =  = (m/v)
It is expressed as kg/m³.
1cm³ = 1ml
 DRY DENSITY
The dry density is defined as the mass of solids per unit total
volume.
d =(md /v) = (ms /v)….. Kg/m³
 SATURATED DENSITY
The saturated density is the bulk density of soil when it is fully
saturated.
sat = (Msat / V) ….. Kg/m³

37
3.1 Explain The Measurement of Geotechnical Design
Parameters.
1. Shear strength
2. Compressive strength
Shear strength Of Soil.
The shear strength is most important property of soil. It is resistance
provided by soil to sliding along any plane inside it. The nature of shear
strength is most difficult to grasp. Shear strength depends on interaction
between particles and shear failure occur when particles slides over each
other due to excessive shearing stresses. It is very much important to
understand behavior and analyze the property of shear strength to
provide soil stability regarding shear failures such as bearing capacity,
slope stability and lateral pressures on earth retaining structures.
Shearing resistance of soil is constituted basically of the structural
resistance, the frictional resistance and cohesion. The shear resistance in
cohesion less soil is of friction alone and in other soils is result of both
friction and cohesion. The shear strength of soil is determined in
laboratory as well as in field.
τf = c + σ’ tan φ
τf = shear strength
c = cohesion
φ = angle of internal friction
Consider the following situation:
 A normal stress is applied vertically and held constant
 A shear stress is then applied until failure

38
 or any given normal stress, there will be one value of shear
stress
 If the normal stress is increased, the shear stress will typically
increase in sands and stay the same in clays
Cohesion
between particles (stress independent component)
•Cementation between sand grains
•Electrostatic attraction between clay particles
Angle Of Friction
Soil friction angle is a shear strength parameter of soils. Its definition is
derived from the Mohr-Coulomb failure criterion and it is used to describe the
friction shear resistance of soils together with the normal effective stress.
In the stress plane of Shear stress-effective normal stress, the soil friction
angle is the angle of inclination with respect to the horizontal axis of the Mohr-
Coulomb shear resistance line.

39
3.2 Discuss the Methods Of Ground Investigation And in situ
sample acquisition and Testing.
The various type of site Exploration.
1. Open excavation.
2. Borings
3. Sub surface sounding
4. Geo physical method
These are site exploration methods. I explain 2 methods in my assignment.
1. Trial pit.
2. Borehole.
TRIAL PIT AND BOREHOLE
• Excavation of ground in order to study or sample the composition
and structure of the subsurface, usually dug during a site
investigation, a soil survey or a geological survey.
• To identify whether the site is suitable for the proposed work.
Trial pit
This method involving the open
excavation. Very cheapest
method in site exploration.
Because can we using any type of
soil in this method.
• Shallow excavations to a depth no greater 6m.
• Support use are timbering, steel frames with hydraulic jack, battered or
tapered side.
• Suitable for most low rise developments.
• Suitable for the investigation of all types of land.

40
Trial pitting can be carried out by a variety of methods from hand
dug pits to machine excavated trenches. Trial pitting is generally carried
out to a maximum depth of 4.5m with standard excavation plant and,
depending on soil conditions, is generally suitable for most low rise
developments.
All trial pit investigations are supervised by experienced engineers with a
thorough understanding of geology and soil mechanics.
Additional testing in trial pits can include soak away testing, CBR testing and
in-situ strength testing.
Borehole
Boreholes are a common method of site investigation. Using a
vehicle-towed rig most sites can be investigated. In-situ testing techniques
including Standard Penetration Testing, Permeability Testing, Borehole Vane
Testing and Packer Testing can all be carried out in the boreholes in order to
provide information for geotechnical design. Continuous disturbed and
undisturbed samples are retrieved from the boreholes for inspection and
logging by engineers and subsequent testing in our laboratories.
The various method commonly used.
 Auger boring.
 Auger and shell boring.
 Wash boring
 Precaution boring
 Rotary boring
 Auger boring.
 Augers are used in cohesive and other soft soils above water
table.
 Operating manually or mechanically.
 Hand augers used depth up to 6m
 Mechanically can also be used in gravelly soil.

41
 Augers are 2 types.
1. Spiral auger
2. Post hole auger
 Augers and shell boring
 Can be used for making deep boring.
 Hand operated rigs are used for depth up
to 25m
 Mechanized up to 50m
 Suitable for soft to stiff clay.
 Shell for very stiff and hard clay.
 Wash boring
 Simple method for advancing holes in all
type of soil.
 Boulders and rock cannot be penetrated by
this method.
 Percussion boring.
 In this method soil and rock formations are
broken by repeated bellows of heavy chisel
or bit suspended by a cable or drill rod.
 Water is added to the hole during boring.
 The method suitable for advancing in all
type of soils.
 Rotary boring.
 Very fast method of advancing hole in both
rocks and soils.
 Drill bit fixed to the lower end of the drill
rods.
 Always kept in firm contact with the
bottom of the hole.

42
3.3 Carry out Laboratory Measurements on soil.
Density in Placed By Sand Cone Test.
Description of Test
This test method describes the procedure for determining the density of soil
cement base
course in place.
APPARATUS AND MATERIALS
Equipment Required
 Sampling tools - hammer, chisel, trowel, large spoon, banister brush.
 Containers - two 2.3 L size mason jars for which the tare weights are
known.
 Balance - 0.1 g accuracy
 Sand Cone Density Apparatus - consisting of a double cone assembly
having a
 cylindrical valve between the cones with an orifice 12.7 mm in diameter.
The upper cone
 will be large enough to serve as a hopper to hold the density sand.
 Density Sand - prepare a supply of air dried clean flowing sand which
passes the 2.00
 mm sieve and is retained on the 900 mm sieve. Thoroughly mix and pre
weigh 5000 g
 samples and store in a clean dry place.
 Sieves - a 18.00 mm, 200 mm, 900 mm and a 400 mm Canadian Metric
Standard Sieve.
 Calibration Mold - a cylindrical mold 127 mm in diameter with 28.6 mm
wide flange
 around the upper rim. The volume of the mold will be stamped into the
metal.
 Drying Equipment - oven - capable of maintaining a temperature of
110oC and a hot plate
 or stove.
 Thermometers - ranging between 35oC to 150oC.

43Determination of Unit Weight by Sand
 Place the calibration mold in a pan.
 Set the sand cone device in place on the flange of the calibration mold
and close
 the valve.
 Place the pre weighed 5000 g sample of density sand in the hopper.
 Open the valve and keep it open until the sand has stopped flowing and
then
 close.
 Reweigh the sand remaining in the hopper.
 The difference between the original (5000 g) and final weight will be the
"weight
 of sand to fill calibration mold and cone."
 The weight of sand to fill the lower cone will be determined in a similar
manner.
 Place the sand cone device on a flat surface and allow the sand (5000 g)
to run
 into the cone. The difference between the original and final weight of
sand in the
 hopper shall be recorded as the "weight of sand to fill cone."
 Calculate the unit weight of sand from the above determinations.
 If a base plate is to be used in the taking of density tests, the plate shall
be placed
 between the flat surface and the cone. Test as above to determine the
weight of
 sand to fill the cone and base plate.
Density-In-Place by Sand Cone
 Select the site to be tested at random or where sample for proctor has
been taken.
 Scrape smooth and remove all loose material at the location to be tested.
 Start a small hole in the center with a hammer and chisel.
 Carefully enlarge the hole outwards and downwards with small hand
tools until
 sufficient material has been removed to fill the two 2.3 L mason jars.
 Exercise extreme care in removing the material so as not to cause a
disturbance to
 surrounding material. Do not project the hole below the level of the
material tobe tested.
 Place all the material removed from the hole in the mason jars except
stone

44
 particles larger than 18 mm. These stones will be replaced in the hole
during the
 volume measurement with density sand. The sealed jars will be taken to
the lab
 and weighed to the nearest gram and the tare weight subtracted. The
result will
 be recorded as "weight of material removed."
 Carefully place and centre the sand cone device over the test hole with
the valve
 closed.
 Place the 5000 g of density sand into the storage hopper of the sand
cone device.
 Turn on the valve.
 If stone particles are to be replaced in the hole, allow a small quantity of
sand to
 run into the hole, close the valve, lift the apparatus, and partially imbed
these
 particles into the sand. Replace the device, turn on the valve, allow the
sand to
 run until the test hole and funnel are completely filled, and turn off the
valve.
 Remove the apparatus and remove the sand from the test hole and place
in a large
 cloth bag along with other used sand for later reclaiming.
 Weigh the unused sand in the hopper to determine the amount of sand
used in the
 test. This weight of sand will be used to obtain the volume of hole and
funnel.
 Remove the soil cement mixture from the two mason jars and mix
thoroughly
 together and obtain a representative sample for moisture
determination.
 Place sample in a suitable tared pan and weigh.
 Dry sample carefully to a constant weight.
 Weigh sample and pan after cooling.
 The difference between the wet and dry weights will be recorded as
"weight of
 moisture" and dry weight less weight of pan will be recorded as "weight
of dry sample.

45Minerals, Rocks & Rock Forming Processes. 2015. Minerals, Rocks & Rock Forming
Processes. [ONLINE] Available at:http://www.indiana.edu/~geol105/1425chap5.htm.
Basalt: Igneous Rock - Pictures, Definition, Uses & More. 2015. Basalt: Igneous Rock -
Pictures, Definition, Uses & More. [ONLINE] Available
at:http://www.geology.com/rocks/basalt.shtml.
Slide Shere Presentations.
8#safe=active&q=common+usage+of+rocks+in+construction. .
2015. . [ONLINE] Available
at:http://www.engr.uconn.edu/~lanbo/CE240LectW032Soilclassification.pdf.
BCAS Engineering Geology Lecture Tute.

Engineering Soil Mechanics (Fawzan Fahry)

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