WATER INFLUENCES DIFFERENT

BEHAVIOURS OF SOIL
PRESENTED BY INDRANIL BANERJEE
ENROLLMENT NO-CEM18005

SUB:ENGINEERING BEHAVIOUR OF SOIL(CE501)

DEPARTMENT OF CIVIL ENGINEERING
TEZPUR UNIVERSITY
1ST SEMESTER,AUTUMN 2018
 CONTENTS
INTRODUCTION

PHYSICAL PROPERTIES OF WATER CHEMICAL PROPERTIES OF WATER

AND BEHAVIOUR IN SOIL AND BEHAVIOUR IN SOIL

Introduction
Capillary Rise
Consolidation
Dilatancy
Dissolution
Fluctuation of ground water
Ionic Dissociation
table
Compaction
Apparent cohesion
Bulking of sand

CONCLUSION

REFERENCE
 INTRODUCTION

 In soils, water is a major driver

of biogeochemical processes.
Chemical reactions that control The availability of water is considered
soil formation and weathering to be one of the most important factors
reactions occur almost for the growth of crops and other
exclusively in liquid water. plants in this article, we explore how
water is the diffusive medium the molecular structure, chemical
that mediates the movement of properties and physical properties of
gases, solutes, and particles in water control the functioning of soils.
soils. Water regulates the
transfer of heat, thereby
helping buffer soil temperature.
 WATER INFLUENCES DIFFERENT BEHAVIOURS OF SOIL

PHYSICAL PROPERTIES CHEMICAL PROPERTIES

OF WATER AND OF WATER AND
BEHAVIOR IN SOILS BEHAVIOR IN SOILS
 PHYSICAL PROPERTIES OF WATER IN SOIL

 A soil mass consist of solid particles which forms a porous structure. Pores of soil
may be filled completely with air, completely with water or partially with air and
water. Water influences various behaviors of soil by various ways.
 When capillary occur then changes comes to the soil.
 When water goes out from soil in consolidation then also soil behavior changes.
 Dilatancy is also a reason for the behavior of soil changing.
 When the ground water table fluctuate the soil behavior changes.
 During compaction for the particular water content dry unit wt. of soil also
changes.
 Apparent cohesion is also the reason for change of soil behavior.
 Bulking of sand is also a reason for change of soil behavior.
 CAPILLARY RISE

Capillary action, or capillarity, is a phenomenon where liquid

spontaneously rises in a narrow space such as a thin tube, or in
porous materials. This effect can cause liquids to flow against
the force of gravity (RM 2001). It occurs because of inter-
molecular attractive forces between the liquid and solid
surrounding surfaces; If the diameter of the tube is sufficiently
small, then the combination of surface tension and forces of
adhesion between the liquid and container act to lift the liquid
.
 Fig.2 Capillary water through
Fig.1 Capillary Rise
pores
In soil when water flows from the ground water table to
upward direction due to the surface tension of water or
capillary action which results in attractive forces between the
particles and is referred as the soil suction. When two soil
particle coming closer the contact area between them
increases which causes the increase of effective stress and
due to the increase of effective stress, shear strength of soil
increases.
 Fig.4 Capilary Rise in soil
Fig.3 Contact area increases
for capillary
 CONSOLIDATION

 When a soil mass is subjected to a compressive force, its volume decreases.

The property of the soil due to which a decrease in volume occurs under
compressive force is known as the compressibility of soil. The compression of
soil can occur due to
 Compression of solid particles and water in the voids
 Compression and expulsion of air in the voids
 Expulsion of water in the voids
 The compression of saturated soil under a steady static pressure is known as
consolidation. It is entirely due to expulsion of water from the voids.
Fig. Terzaghi Spring Analogy
 Initial Consolidation
 When a load is applied to a
partially saturated soil, a decrease
in volume occurs due to expulsion
and compression of air in the
voids. A small decrease in volume
occurs due to compression of solid
particles. The reduction in volume
of the soil just after the
application of the load is known as
initial consolidation or initial
compression. For saturated soils,
the initial consolidation is mainly
due to compression of solid
particles.
 Primary Consolidation
 After initial consolidation,
further reduction in volume
occurs due to expulsion of water
from the voids. When a
saturated soil is subjected to a
pressure, initially all the applied
pressure is taken up by water as
an excess pore water pressure. A
hydraulic gradient will develop
and the water starts flowing out
and a decrease in volume
occurs. This reduction in volume
is called as the primary
consolidation of soil.
 secondary Consolidation
 The reduction in volume
continues at a very slow rate
even after the excess
hydrostatic pressure developed
by the applied pressure is fully
dissipated and the primary
consolidation is complete. The
additional reduction in the
volume is called as the
secondary consolidation.
 Due to the consolidation the
volume decreases, soil particle
coming closer, effective stress
increases and due to which
shear strength of soil increases.
 DILATANCY

 The phenomenon of dilatancy can be observed in a simple shear test on a

sample of dense sand. In the initial stage of deformation, the volumetric
strain decreases as the shear strain increases. But as the stress approaches its
peak value, the volumetric strain starts to increase. After some more shear,
the soil sample has a larger volume than when the test was started.
 The amount of dilation depends strongly on the density of the soil. In general,
the denser the soil the greater the amount of volume expansion under shear.
  In the time of dilatancy negative
pore water pressure developed
which causes the increases of
effective stress.
 When the effective stress increases
shear strength of soil also
increases.

Fig. Dilatancy of sand

FLUCTUATION OF GROUND WATER TABLE

 If the water level is below

ground level and if water level
decreases the effective stress
increases. If the unit wt of
water is γw and the height
decreases is h then effective
stress will increases by hγw.
With the increases of effective
stress the shear strength of soil
also increases.
 SWELLING

 Rigid or non swelling soils do not

change their specific volume, ν,
and hence, their bulk density ρb
during their water content θ
variation range. In contrast,
extensively swelling soils undergo
significant bulk density, ρb,
variations during their water
content, θ, variation range. They
are usually fine – textured, with
smectitic type of clays.
 The process of swelling is
mainly caused by the
intercalation of water
molecules entering to the
inter-plane space of
smectite clay minerals
(after Low and Morhaim
1979, Schafer and Singer
1976, Parker et al. 1982).
Fig. A diagram showing the intercalation of
water molecules in the inter-plane space of
clay smectites.
 COMPACTION

 Compaction is the application of

mechanical energy to a soil so as to The Objectives Of Compaction Are:
rearrange its particles and reduce
the void ratio.
It is applied to improve the  To increase soil shear strength and
properties of an existing soil or in the therefore its bearing capacity.
process of placing fill such as in the
construction of embankments, road  To reduce subsequent settlement
bases, runways, earth dams, and under working loads.
reinforced earth walls. Compaction is  To reduce soil permeability making it
also used to prepare a level surface more difficult for water to flow
during construction of buildings. through.
There is usually no change in the
water content and in the size of the
individual soil particles.
 COMPACTION

 In compaction test the dry unit wt

indicates the compactness of soil
at a particular water content. If
we repeat the compaction test for
different water content then
maximum dry unit weight will be
achieved at a particular water
content that is Optimum Moisture
Content or OMC. If we further
increase the water content then
the dry density will be decreases,
particles becomes looses, strength
decreases.
 APPARENT COHESSION

 If we draw the Mohr circles

corresponding to total stress
and effective stress then we
will get different Mohr Failure
Envelop. So the corresponding
Cohesion value will also be
changed. Corresponding to
effective stress Mohr Failure
Envelop we will get more
cohesion value which is
termed as Apparent Cohesion.
For the existence of apparent
cohesion the soil particles will
come closer. Shear strength of
the soil increases.
 BULKING OF SAND

 The volume of a given quality of Sand varies according to its moisture

content. If the sand is wet, particles get a covering of water, which due
to surface tension, keeps them separately and thus causes an increase
in volume known as “Bulking“.
 Bulking increases gradually with moisture content and the increase in
volume may reach ~35% by volume at 5% – 6% moisture content by
weight. It then decreases down to zero, when the quantity of water
becomes more than ~25% (as if they are fully compacted).
 The Bulking
increases with
fineness of
sand, because
of large surface
area
contributed by
fine particles
for the same
volume
contribution.

Fig. Bulking of sand

 CHEMICAL PROPERTIES OF WATER AND
BEHAVIOR IN SOILS

The chemical properties of water behavior in the environment and control many
processes occurring in soils as the aqueous phase interacts with organisms, mineral
surfaces, and air spaces. As a result of its nonlinear structure and dipole moment
water has a high dielectric constant. which is a measure of a substance's ability to
minimize the force of attraction between oppositely charged species.
Water's dielectric constant, which is significantly higher than that of the solid and
gaseous components of soil (dielectric constants of ~2-5 and 1, respectively), is
often utilized in electromagnetic measurement approaches to determine soil water
content.
This unique property of water also makes it a powerful solvent, allowing it to
readily dissolve ionic solids. Water acts to dissipate the attractive force of ions by
forming solvation spheres around them. The polar nature of the water molecules
allow them to surround and stabilize the charges of both anions and cations,
preventing their association.
 DISSOLUTION

 potassium chloride (KCl) combined with water, the ionic solid dissolves:

 KCl(s) + (m+n)H2O(l) ↔ [K(H2O)m]+(aq) + [Cl(H2O)n]-(aq)

 where m and n represent the numbers of water molecules— numbers that are
functions of the charge, size, concentration, and chemical properties of the ions
in solution.
 Water's ability to enhance dissolution or prevent precipitation impacts a range of
processes and properties in soils, including mineral weathering, soil salinity, and
soil fertility.
DISSOLUTION
 IONIC DISSOCIATION

 Due to polarity, water readily undergoes ionic dissociation into protons and
hydroxide ions:
 H2O(l) ↔ H+(aq) + OH-(aq) (1)
 Accordingly, when it reacts with a strong base, water acts as an acid,
releasing protons:
 H2O(l) + NH3 ↔ NH4+(aq) + OH-(aq) (2)
 When it reacts with a strong acid, water acts as a base, accepting protons:
 H2O(l) + HCl ↔ H3O+(aq) + Cl-(aq) (3)
 In aerobic soils, water is produced from the oxidation of carbon in organic
matter (here notated as CH2O) for energy production by microorganisms:
 CH2O(s) + O2(g) → CO2(g) + H2O(l) (4)
IONIC DISSOCIATION
 CONCLUSION

 If we consider three phase system for soil then soil solid, water and air will
comes. With the changes of three phase system, various changes of soil
behavior occur. Changes occur with the compression of soil and also with the
water content. And with the changes of three phase, soil strength also
changes. As water changes is the reason of three phase changes so we can
conclude that the water influences different behavior of soil.
 REFERENCE

 Mitchell,J.K and Soga,Kenichi,Fundamentals of Soil Behaviors,John Wiley &

Sons,2005.
 Ranjan,G.&Rao,A.S.R(2016) Basic And Applied Soil Mechanics. New Delhi: New
Age International Publisher.
 International Journal of Scientific & Engineering Research, Volume 5, Issue 3,
March-2014 1416 ISSN 2229-5518
 International Journal of Scientific & Engineering Research, Volume 5, Issue 7,
July-2014 ISSN 2229-5518
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