Physical Properties of sediments and water sediment mixture

1. Physical Properties of sediments
and water sediment mixture
Lecture 3
Jyoti Khatiwada
Roll no. 10

2. Mass Density and specific wt of solid
particles
• The particle density or true density of a
particulate solid or powder, is the density of the
particles that make up the powder, in contrast to
the bulk density, which measures the average
density of a large volume of the powder in a
specific medium (usually air).
• These mass and volume definitions can be used
to define the concepts of soil particle density,
bulk (dry) soil density, and total (wet)
soil density.

3. • Density represents weight (mass) per unit volume of a substance.
• Density = Mass / Volume
• Soil density is expressed in two well accepted concepts as particle density
and bulk density. In the metric system, particle density can be expressed in
terms of mega grams per cubic meter (Mg/m3). Thus if 1 m3 of soil solids
weighs 2.6 Mg, the particle density is 2.6 Mg / m3 (since 1 Mg =1 million
grams and 1 m3 =1 million cubic centimeters) thus particle density can
also be expressed as 2.6 g / cm3.
• Particle Density: The weight per unit volume of the solid portion of soil is
called particle density. Generally particle density of normal soils is 2.65
grams per cubic centimeter. The particle density is higher if large amount
of heavy minerals such as magnetite; limonite and hematite are present in
the soil. With increase in organic matter of the soil the particle density
decreases. Particle density is also termed as true density.
Textural
classes
Particle density
( g/ cm3)
Coarse sand 2.655
Fine sand 2.659
Silt 2.798
Clay 2.837

4. • Bulk Density: The oven dry weight of a unit volume of soil inclusive of pore spaces
is called bulk density. The bulk density of a soil is always smaller than its particle
density. The bulk density of sandy soil is about 1.6 g / cm3, whereas that of organic
matter is about 0.5. Bulk density normally decreases, as mineral soils become finer
in texture. The bulk density varies indirectly with the total pore space present in
the soil and gives a good estimate of the porosity of the soil. Bulk density is of
greater importance than particle density in understanding the physical behavior of
the soil. Generally soils with low bulk densities have favorable physical conditions.
• Factors affecting bulk density
• 1. Pore space: Since bulk density relates to the combined volume of the solids and
pore spaces, soils with high proportion of pore space to solids have lower bulk
densities than those that are more compact and have less pore space.
Consequently, any factor that influences soil pore space will affect bulk density.
• 2. Texture: Fine textured surface soils such as silt loams, clays and clay loams
generally have lower bulk densities than sandy soils. This is because the fine
textured soils tend to organize in porous grains especially because of adequate
organic matter content. This results in high pore space and low bulk density.
However, in sandy soils, organic matter content is generally low, the solid particles
lie close together and the bulk density is commonly higher than in fine textured
soils.
• 3. Organic matter content: More the organic matter content in soil results in high
pore space there by shows lower bulk density of soil and vice-versa.

5. Bulk or Mass density of different class
Textural class
Bulk density (g/cc) Pore space
(%)
Sandy soil 1.6 40
Loam 1.4 47
Silt loam 1.3 50
Clay 1.1 58

6. Specific wt of particles
• The specific weight (also known as the unit weight) is
the weight per unit volume of a material. The symbol
of specific weight is γ (the Greek letter Gamma)

7. Submerged unit weight
• Submerged unit weight, which is defined as the
difference between the saturated unit weight
and the unit weight of water. It is often used in
the calculation of the effective stress in a soil.

8. Specific gravity
• Specific gravity is the ratio of the density of a
substance to the density of a reference
substance; equivalently, it is the ratio of the
mass of a substance to the mass of a reference
substance for the s ame given volume.

9. Grain size classification

10. Fall Diameter and nominal diameter
• Standard Fall Diameter - The standard fall
diameter of simple fall diameter, of a particle
is the diameter of a sphere that has a specific
gravity of 2.65 and has the same standard fall
velocity as the particle.
• Nominal Diameter - The nominal diameter of
a particle is the diameter of a sphere that has
the same volume as the particle.

11. Gradation coefficient
• The Coefficient of Gradation is defined as:
• where

12. Probablity plots and various measure
of size distribution
• The particle-size distribution (PSD) of a powder, or
granular material, or particles dispersed in fluid, is a list
of values or a mathematical function that defines the
relative amount, typically by mass, of particles present
according to size. Significant energy is usually required
to disintegrate soil, etc. particles into the PSD that is
then called a grain size distribution.
• The normal probability plot is a graphical technique to
identify substantive departures from normality. This
includes identifying outliers, skewness, kurtosis, a need
for transformations, and mixtures. Normal probability
plots are made of raw data, residuals from model fits,
and estimated parameters.

13. Normal probablity plot

14. Measure of grain size distribution
• I. Grain Size Analyses Since particle diameters typically span many
orders of magnitude for natural sediments, we must find a way to
conveniently describe wide ranging data sets. The base two
logarithmic f (phi) scale is one useful and commonly used way to
represent grain size information for a sediment distribution. A
tabular classification of grain sizes in terms of f units, millimeters,
and other commonly used measurement scales is included for
purposes of comparison

21. Shape factor , form , sphericity and
roundness
• The roundness classes are based upon another Wadell
roundness index given by;
• ρ =r/R
• where r is the radius of curvature of the largest inscribed
circle and R is the radius of the smallest circumscribing
circle. The index ranges from 0 to 1, with 1 indicating a
perfect circle. The roundness classes are based upon a
logarithmic scale because the distinction of differences at
the high roundness end of the scale is more difficult than at
the low roundness end of the scale. The class between 0.00
and 0.12 is excluded, because natural particles generally
have roundness values greater than 0.12.

23. Sphericity

26. • Sediment Maturity refers to the length of time that the
sediment has been in the sedimentary cycle. Texturally mature sediment is
sediment that is well rounded, (as rounding increases with transport
distance and time) and well sorted (as sorting gets better as larger clasts are
left behind and smaller clasts are carried away. Because the weathering
processes continues during sediment transport, mineral grains that are
unstable near the surface become less common as the distance of transport
or time in the cycle increases. Thus compositionally mature sediment is
composed of only the most stable minerals.
• For example a poorly sediment containing glassy angular volcanic
fragments, olivine crystals and plagioclase is texturally immature because
the fragments are angular, indicating they have not been transported very
far and the sediment is poorly sorted, indicating that little time has been
involved in separating larger fragments from smaller fragments. It is
compositionally immature because it contains unstable glass along with
minerals that are not very stable near the surface - olivine and plagioclase.
• On the other hand a well sorted beach sand consisting mainly of well
rounded quartz grains is texturally mature because the grains are rounded,
indicating a long time in the transportation cycle, and the sediment is well
sorted, also indicative of the long time required to separate the coarser
grained material and finer grained material from the sand. The beach sand
is compositionally mature because it is made up only of quartz which is very
stable at the earth's surface.

27. Shape factor
• Shape factors are dimensionless quantities used in image
analysis and microscopy that numerically describe the
shape of a particle, independent of its size. Shape factors
are calculated from measured dimensions, such as
diameter, chord lengths, area, perimeter, centroid,
moments, etc. The dimensions of the particles are usually
measured from two-dimensional cross-sections or
projections, as in a microscope field, but shape factors
also apply to three-dimensional objects.
• Shape factors are often normalized, that is, the value
ranges from zero to one. A shape factor equal to one
usually represents an ideal case or maximum symmetry,
such as a circle, sphere, square or cube.

28. forms
A simple classification by zingg in 1935 used the
ratio of width to length (b/a) and thickness by
breadth (c/b) . These ratios are called forms
indices. Every shape particle applies from
indices to define form of particles.
Four different shape nomenaclature are
Tabular(rod), equant, bladed and prolate (disc)

29. Sorting packing and orientation of
particles
• Sorting describes the distribution of grain size of sediments,
either in unconsolidated deposits or in sedimentary rocks.
Very poorly sorted indicates that the sediment sizes are
mixed (large variance); whereas well sorted indicates that
the sediment sizes are similar (low variance).
• The terms describing sorting in sediments - very poorly
sorted, poorly sorted, moderately sorted, well sorted, very
well sorted - have technical definitions, and semi-
quantitatively describe the amount of variance seen in
particle sizes
• The degree of uniformity of grain size. Particles become
sorted on the basis of density, because of the energy of the
transporting medium. High energy currents can carry
larger fragments. As the energy decreases, heavier
particles are deposited and lighter fragments continue to
be transported. This results in sorting due to density.

30. Sediment consisting of
well sorted grains (left) poorly sorted grains (right).

31. Packing and orientation of grains
• Elements of the sediment show dimensional relations
among them, expressed by various kinds of contact of
adjacent grains. This kind of relationship, for the grains
forming a grain skeleton, is called PACKING. It is a
feature specifying dimensional density of grains in a
sedimentary rock.
Besides packing, grains can show directional
arrangement in space, which is called a GRAIN
ORIENTATION. Especially long and flat grains can be
arranged in a rock in a way that is an oriented structure

32. Packing of grains

33. Porosity

34. Porosity
Porosity is the quality of being porous, or full of tiny
holes. Liquids go right through things that
have porosity. Go
back far enough
and you'll find that
porosity stems
from the Greek
word poros for
"pore," which means “
passage.” So something
withporosity lets
things through

35. Void ratio
• e = (V_v) / (V_s)
• Where V_v is the volume
of the voids (empty or
filled with fluid),
• and V_s is the volume of
solids.
• Void ratio is usually used in
parallel with soil porosity
(n) , which is defined as the
ratio of the volume of
voids to the total volume
of the soil.

36. Dry specific weight
The specific weight (also known as the unit
weight) is the weight per unit volume of a
material. The symbol of specific weight is γ (the
Greek letter Gamma).
Not to be confused with specific gravity
Dry specific weight =Dry wt of sediments
/total volume
Dry specific mass =Dry mass of
sediments/total volume

37. Newtonian mixture

38. Newtonian Fluids
• Newtonian fluids are named after Sir Issac Newton (1642 - 1726)
who described the flow behavior of fluids with a simple linear
relation between shear stress [mPa] and shear rate [1/s]. This
relationship is now known as Newton's Law of Viscosity, where
the proportionality constant η is the viscosity [mPa-s] of the fluid:
• Some examples of Newtonian fluids include water, organic
solvents, and honey. For those fluids viscosity is only dependent
on temperature. As a result, if we look at a plot of shear
stress versus shear rate we can see a linear increase in stress with
increasing shear rates, where the slope is given by the viscosity of
the fluid. This means that the viscosity of Newtonian fluids will
remain a constant) no matter how fast they are forced to flow
through a pipe or channel (i.e. viscosity is independent of the rate
of shear).

40. viscosity
• Viscosity is a property arising from collisions
between neighboring particles in a fluid that are
moving at different velocities. When the fluid is
forced through a tube, the particles which
compose the fluid generally move more quickly
near the tube's axis and more slowly near its
walls; therefore some stress (such as
a pressure difference between the two ends of
the tube) is needed to overcome the friction
between particle layers to keep the fluid moving.
For a given velocity pattern, the stress required is
proportional to the fluid's viscosity.

41. Dynamic viscosity

42. Dynamic viscosity of newtonian mixture

43. dynamic (shear) viscosity
• The dynamic (shear) viscosity of a fluid
expresses its resistance to shearing flows,
where adjacent layers move parallel to each
other with different speeds. It can be defined
through the idealized situation known as a
Couette flow, where a layer of fluid is trapped
between two horizontal plates, one fixed and
one moving horizontally at constant speed u.

44. Kinematic viscosity

45. Kinematic viscosity of newtonian
mixture
• The kinematic viscosity (also called
"momentum diffusivity") is the ratio of the
dynamic viscosity μ to the density of the
fluid ρ. It is usually denoted by the Greek
letter nu .

46. Volumetric sediments concentration

47. The End.
• Thank you