A brief report about clay minerals and geotechnical problems - Geology fully made by Amira Abdullah (civil engineering student in Ismailia - Egypt)

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CLAY MINERALS &
GEOTECHNICAL PROBLEMS
Faculty of Engineering – Civil Eng. Department
By: Amira Abdallah Youssef Ibrahim
To: Dr. Salah Shata

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Clay Minerals
 Definition
Clay refers to naturally occurring material composed primarily of fine-
grained minerals, which is generally plastic at appropriate water
contents and will harden when fired or dried.
The minerals found in clay are generally silicates less than 2 microns
(one millionth of a meter) in size, about the same size as a virus. Clays
are very abundant at the earth's surface; they form rocks known as
shales and are a major component in nearly all sedimentary rocks. 1
 Importance
Clay contributes many benefits to the physical, chemical and biological
properties of soil. It increases the soil’s cation exchange capacity,
enhances waterholding capacity, provides elasticity, acts as a binding
agent for the non-clay components, and reduces nutrient loss through
leaching. The buffering capacity of soil (resistance to change in pH) is
enhanced by clay, which means that growers do not have to apply
lime as often. Clay is an essential component of a productive soil. It
plays a vital role
in holding plant
nutrients and
water. Without
it, successful
crop production
would be in
jeopardy.2
1 -INTRODUCTION TO THE PROPERTIES OF CLAY MINERALS Stephen Guggenheim Department of Geological
Sciences University of Illinois at Chicago
2- Clay Minerals: Their Importance and Function in Soils by Tucker, M. Ray.

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 Types of Clay minerals :
There're four
basic types of clay
minerals .3
Kaolinite: This clay mineral is the weathering
product of feldspars. It has a white, powdery
appearance. Kaolinite is named after a locality
in China called Kaolin, which invented
porcelain (known as china) using the local clay
mineral. The ceramics industry uses it
extensively. Because kaolinite is electrically
balanced, its ability of adsorb ions is less than
that of other clay minerals.
Illite: Resembles muscovite in mineral
composition, only finer-grained. It is the
weathering product of feldspars and felsic
silicates. It is named after the state of Illinois, and
is the dominant clay mineral in midwestern soils.
Chlorite: This clay mineral is the
weathering product of mafic silicates and
is stable in cool, dry, or temperate
climates. It occurs along with illite in
midwestern soils. It is also found in some
metamorphic rocks, such as chlorite
schist.
3 Journal of Natural Resources and Life Sciences Education

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Vermiculite: This clay mineral has the
ability to adsorb water, but not
repeatedly. It is used as a soil additive for
retaining moisture in potted plants, and
as a protective material for shipping
packages.
Smectite: This clay mineral is the
weathering product of mafic silicates, and is
stable in arid, semi-arid, or temperate
climates. It was formerly known
as montmorillonite. Smectite has the ability
to adsorb large amounts of water, forming a
water-tight barrier. It is used extensively in
the oil drilling industry, civil and
environmental engineering (where it is
known as bentonite), and the chemical
industry.

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 Engineering Characteristics
Changes in soil water content or solution chemistry of clayey soils induce
swelling pressures sufficiently large to fracture and damage structures
and roads.4
Swelling process
Clay minerals, such as smectites and mixed-layer illites, can expand in
volume up to 20 times their
original volume through
adsorption of layers of water
between their unit cells. Such
2:1 clay minerals are
particularly prone to swelling
because there is no hydrogen
bonding between the
octahedral layers of the unit
cells.
Swelling is known to occur in
three steps. In the first step, referred to as crystalline swelling, layers of
Jones Jr., F.O. 1964. Influence of Chemical Composition of Water on Clay Blocking of Permeability. J4
Pet Technol 16

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water enter the interlayer space in the clay mineral, resulting in an
increase in the C spacing of the clay mineral in steps. The size of these
steps is observed to be approximately equal to the diameter of the water
molecule
The next stage in swelling is referred to as hydration swelling. This is
thought to occur through the hydration and dehydration of ions entering
the interlayer region.
Several theories have
been proposed to
explain the observed
repulsive hydration force
observed in the
presence of different
cations.
Finally, when the
interlayer spacing is ≈ 50
Å or so, free swelling
occurs. This is driven
primarily by the balance
between electrostatic and van der Waals forces between the layers of
clay. In this stage of swelling, the clay layers are sufficiently far apart that
very little mechanical integrity exists in the clay. Such clay minerals are
liable to be dispersed in the flowing fluid and to plug pore throats.
Shrinkage
Shrinkage is the rate at which the body
shrinks during drying and firing .
Moist clay begins to shrink as soon as it is
taken out of its plastic storage bag and comes
into direct contact with the air. Water is
drawn out of the clay until it reaches the
moisture content of the surrounding
atmosphere.

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 Effects of swelling and shrinkage on Structures
Foundation Damage The most obvious way in which expansive
soils can damage foundations is by uplift as they swell with
moisture increases. Swelling
soils lift up and crack lightly-
loaded, continuous strip
footings, and frequently cause
distress in floor slabs. Because
of the different building loads
on different portions of a
structure's foundation, the
resultant uplift will vary in
different areas.5
DAMAGE TO FOUNDATIONS FROM EXPANSIVE SOILS J. David Rogers, Robert Olshansky, and Robert5
B. Rogers

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Road damage (Asphalt cracks)
Mud flow & Debris flow

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 Engineering Solutions For Geotechnical Problems
Pile Foundations
A pile is basically a
long cylinder of a
strong material such
as concrete that is
pushed into the
ground to act as a
steady support for
structure built on the
top of it .
Types of Piles due to depth
Material used in piles

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Piles
Foundation
Driven
Piles
Micro
piles
Concrete
Piers
Helical
Piers
Helical Piers

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Concrete Piles
Micro Piers

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Other Solutions :

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