waterinfluencesdifferentbehavioursofsoil

1. PRESENTED BY INDRANIL BANERJEE
ENROLLMENT NO-CEM18005
SUB:ENGINEERING BEHAVIOUR OF SOIL(CE501)
DEPARTMENT OF CIVIL ENGINEERING
TEZPUR UNIVERSITY
1ST SEMESTER,AUTUMN 2018

2. CONTENTS
INTRODUCTION
Introduction
Capillary Rise
Consolidation
Dilatancy
Fluctuation of ground water table
Compaction
Apparent cohesion
Bulking of sand
Dissolution
Ionic
Dissociation
CONCLUSION
REFERENCE

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

4. WATER INFLUENCES DIFFERENT
BEHAVIOURS OF SOIL
PHYSICAL
PROPERTIES
OF WATER
AND
BEHAVIOR IN
SOILS
CHEMICAL
PROPERTIES
OF WATER
AND
BEHAVIOR IN
SOILS

5.  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.

6. 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 .

7. Fig.1 Capillary Rise Fig.2 Capillary water through pores

8. 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.

9. Fig.3 Contact area increases Fig.4 Capillary Rise in soil for capillary

10.  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.

11. Fig. Terzaghi Spring Analogy

12.  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.

13.  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.

14.  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.

15.  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.

16.  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

17.  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.

18.  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.

19.  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.

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

21.  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.

22.  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.

23.  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).

24.  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

25. 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.

26.  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.

27. Fig:DISSOLUTION

28.  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)

29. Fig:IONIC DISSOCIATION

30.  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.

31.  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