WATER INFLUENCE BEHAVIOURS IN SOIL

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WATER INFLUENCES DIFFERENT BEHAVIOURS OF SOIL

• PRESENTED BY INDRANIL BANERJEEENROLLMENT
  NO-CEM18005
• SUBENGINEERING BEHAVIOUR OF SOIL(CE501)
• DEPARTMENT OF CIVIL ENGINEERING
• TEZPUR UNIVERSITY
• 1ST SEMESTER,AUTUMN 2018

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CONTENTS
INTRODUCTION
PHYSICAL PROPERTIES OF WATER AND BEHAVIOUR IN
SOIL
CHEMICAL PROPERTIES OF WATER AND BEHAVIOUR IN SOIL
Introduction Capillary Rise Consolidation Dilatanc
y Fluctuation of ground water table Compaction App
arent cohesion Bulking of sand
Dissolution Ionic Dissociation
CONCLUSION
REFERENCE
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INTRODUCTION

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

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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 .

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

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

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Fig. Terzaghi Spring Analogy
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• 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.

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• 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.

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• 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.

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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.

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• 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
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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 ?w and the
  height decreases is h then effective stress will
  increases by h?w. With the increases of effective
  stress the shear strength of soil also increases.

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SWELLING

• Rigid or non swelling soils do not change their
  specific volume, ?, and hence, their bulk density
  ?b during their water content ? variation range.
  In contrast, extensively swelling soils undergo
  significant bulk density, ?b, variations during
  their water content, ?, variation range. They are
  usually fine textured, with smectitic type of
  clays.

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• 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.
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COMPACTION

• 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.

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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.

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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.

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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).

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• 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
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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.

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DISSOLUTION

• potassium chloride (KCl) combined with water, the
  ionic solid dissolves
• KCl(s)  (mn)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.

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DISSOLUTION
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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)

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IONIC DISSOCIATION
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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.

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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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