Having discussed lot of things regarding environmental
geomechanics now, this is the time to start
formally the concepts which are picking up
in this domain and I will start discussion
on soil water environment interaction, this
is a very contemporary topic which is being
studied by lot of people all over the world
until now, you have discussed mostly soil
water interaction in your undergraduate course.
Remember, whatever experiments you are done,
you have created an interaction between soil
and water, starting from the hydrometer test
where you allowed water to interact with the
soil and then you try to analyse how this
interaction occurs and you know how the settlement
of the grains of the soil takes place. Beautiful
example of soil water interaction is the Atterberg
limits.
When soil comes in contact with water whether
it loses its shear strength or not, is a very
interesting philosophy similarly, the plastic
limit, shrinkage limit indirectly these are
the philosophies which deal with interaction
of soils with water and then we have hypothesized
liquid limit, plastic limit, shrinking limit
and so on to characterize the soil in a better
manner. Similarly, compaction characteristics
you know, how soil and water when they react
with each other, interact with each other.
And when external stresses the impact loading
comes on them and what happens, when the material
gets compacted is another interesting example
of you know, how compaction characteristics
can be utilized to define soil water interaction.
So, if you look at the compaction curve on
the y-axis, we plot gamma dry though we have
added water but mathematically, we have filtered
out the water to convert it into gamma D.
And we plot gamma D with respect to moisture
content, it is also a good example of how
soil water interaction occurs. A consolidation
is another interesting example you know, where
soils are saturated and then you are interested
in knowing how the pore pressure develops
when the soil in the saturated state is externally
loaded and of course, the shear strength theory
which all of you are aware of dry soils would
not have much strength.
Of course, you can have shear strength provided
their OC materials over consolidated materials,
now what I am going to do is I am going to
superimpose on soil water interaction, the
influence of environment and you must have
realized the way I have defined environment
is or the attributes of environment are the
nature mostly, you know solar cycle, humidity,
temperature, pressure different type of environmental
conditions which can be replicated.
So, now we want to study how soil water environment
interaction occurs and this is you know more
comprehensive as compared to the soil water
interaction which you have studied until now.
So, with this in view, we need to deal with
the first of all the definition of soil water
interaction, environment interaction, the
natural environment, all of you are aware
of this how human activities have modified
this to man-made environment.
We will try to understand what are the components
of these 2, then of course what is the response
of the soil to environment, different types
of environments, elevated temperatures, high
pressures, low pressures, low temperatures
you know, different types of chemicals you
know coming in contact with the soil in a
saturated dry or a semi saturated form and
so on. Then of course, we will be talking
about the basic concepts analysis of geomechanics
problems you know, how geomechanics; conventional
geomechanics deals with the issues.
What are the basic concepts and after having
done all these things, we will bulldoze the
conventional geomechanics, so we will find
out what are the flaws in conventional classical
geomechanics which have to be rectified, if
we want to study soil water environment interaction
in a better manner. I hope by this time must
have been clear to you that the conventional
subject is not very you know, complete.
There are lot of loopholes and I have been
specifying and trying to highlight this concept
until now, so that you assimilate this thought.
So, let us start with this now, this is the
matrix which I would like to share with you
that what is the genesis of soil water environment
interaction. So, on one hand we have natural
environment and on the second hand, we have
man-made environment and both of these are
influencing the geo micro biosphere, if you
remember some time back I had used this word
geo micro biosphere which is the complete
sphere you know, the sustenance occurs in
this.
Geo is something which comes out of the ground,
micro biosphere is the one which constitutes
most of the processes or most of the mechanisms
or the soil mass itself so, if you remember
the weathering process of the soils itself
could be microbial, alright and so this is
a genesis of the material. Now, what we are
trying to understand is that how natural environment
and man-made environment influence the geo
micro biosphere.
And to quantify this concept because until
now, I think we have spoken a lot, everything
was abstract, we have not use any sort of
a hypothesis or a theory, people have proposed
the particle energy field theory and the pronunciator
of this theory was professor H. Y. Fang who
has considered the geomaterial the particle
which is sitting in an energy field alright.
So, for a quick example I am sure you must
have realized you know, how a charge sitting
inside a parallel plate capacitor behaves,
you must heard in your 10+2 physics, for that
matter even in an x-ray cathode tube you know,
the x-ray beams are travelling and then you
have electromagnetic force or electromagnetic
field and you have electric field and magnetic
field, so this is the electromagnetic field.
And then you want to find out what is the
path traverse by the electron alright, this
is a beautiful examples so similarly, this
concept we will now extend to the soils or
the geo materials, this could be rocks, this
could be soils, this could be groundwater
and we want to see what is an influence of
different types of energy fields and energy
fields are going to depict environment alright.
And the whole idea is that we would like to
use this concept to solve the problems of
the environmental geotechnical engineering
or geoenvironmental issues, which are bothering
the society. Now, if you want to deal with
this theory basically, we have to understand
the response of the geomaterials in 2 forms;
one is the short term or another one is the
long term so, most of the practices of conventional
geomechanics were short term you know.
The consolidation also was completed within
few days but suppose, if I want to study in
a prolonged manner what is happening after
let us say, 1 year of testing of the soil
sample in a falling head permeameter, alright
and particularly, when the permeant; permeant
means the fluid which is passing through the
soils is not pure water, it might be having
contaminants.
And if you remember the attributes of the
contaminant which we have defined are elevated
temperature, very high concentration of chemicals,
very high radioactivity, microbial activity
you know, it could be charges also, electrical
charges so, all these things constitute to
the a contaminant. So, imagine a fluid which
is having all these attributes is now passing
through the porous media and I want to understand
the short term and long-term behaviour of
the permeation.
So, I am sure now with this concept and whatever
background I have given to you, you can realize
this is going to be a very intricate subject
to study. So, the challenge is how to model
the behaviour in the short term and long term
to, by using the particle energy field theory
to get the solutions to the problems which
we are talking about. Now, it so happens that
when you are dealing with this particle energy
field theory, you will realize that the background
from different subjects is required.
You must have got a feel of this, the way
I have been discussing, it is a multidisciplinary
subject alright, it is not confined to a particular
stream as such so, to my knowledge when you
deal with particle energy field theory, the
knowledge of bacteriology; we were talking
about how bacteria migrates from one place
to another place in the porous media.
And just now I gave you an idea that the fluid
which is passing through the porous media
in a falling head testing device might be
containing pathogens, might be containing
bacteria might be containing microbes whatever
so, I want to see how the concentration in
the microbes is changing in the porous system
with respect to time and with respect to the
distance, alright.
So, bacteriology, biology, chemical engineering,
climatology, geohydrology, geophysics, geochemistry,
hydrogeology, mechanics of course you cannot
be forgotten, micro geology, physico chemistry
and soil sciences and soil engineering and
toxicology, so these are the subjects which
have to be you know dealt with when you are
talking about the application of particle
energy field theory.
So, this is what explains you know or with
this what I am trying to do is; I am just
trying to set the tone for the discussion
on soil water environment interaction.
If you try to understand what is meant by
the natural environment, I think we can define
it easily whatever nature had given us beautiful
you know, stream of water, if you go about
10, 20, 40 kilometres away from Bombay city,
you will find very serene environment particularly,
when it rains it looks so beautiful and so
this type of serenity is getting lost alright.
Because of the whatever genesis we have talked
about of the environmental geomechanics now,
this is what we say the atmosphere, so atoms
you know, Atmos, it is the vapours or the
dust, atmosphere consist of the vapours and
the dusts and we talk about the biosphere,
so biosphere is the one in which the flora
and fauna survives and this survive is because
of the oxygen, nitrogen and carbon cycle.
And these cycles are basically, the cycle
of the nature, you must have studied in your
10, +2, I am just remind you, so then we talk
about the hydrosphere; hydro is water and
you know the water is present in different
forms and these forms are it could be in the
oceans, it could be in the lakes, it could
be in the aquifers, it could be in the form
of the ice, or it could be in the form of
the clouds.
So, if you remember we have talked about all
these things; frozen state geomechanics deals
with the water in different states you know,
in the geomaterials. We talk about the lithosphere;
lithos is the stone alright so, we talk about
stones, rocks, soils and hence the natural
environment consists of atmosphere, biosphere,
hydrosphere, lithosphere and geo micro biosphere.
So, what is geo micro biosphere? This is basically,
ecosphere which consists of the entire thing.
Now, what we would like to do is; this is
something which is of interest to the climatologist,
those who talk about the climate sensors.
Now, we are more interested in starting from
this as a benchmark you know what has happened
because of industrialization, because of overpopulation,
because of land you know scarcity, because
of the resource scarcity and so on.
We would like to understand first what are
the natural components, what are the components
of the natural environment and then we will
try to see how these natural components have
got shifted or changed because of the present
day civilization. So, geo micro biosphere
or eco sphere talks about the trees, vegetation,
roots, bacterial activities in the soils and
water and overall response.
So, sometime back I was citing here that the
contemporary geomechanics deals with soil,
root zone, microbes, environment interaction
so, if you have studied this editorial which
I wrote you must have realized that this is
where the more emphasis is right now and people
are trying to understand how vegetation can
be utilized for stabilization of the slopes
alright, these are bio-inspired geotechnical
engineering practices.
So, if roots can you know stabilize the soil
and if the soil cover stabilizes the slope,
can I use this concept to do reverse engineering
or bioengineering to make the system stable.
So, coming to the man-made environment you
know, what human activities have done sorry,
before that I will discuss the cycle of the
nature which I am sure you must be aware of;
oxygen cycle is something which is the genesis
of the oxides you know, which are present
in the soils or for that matter in any matter.
So, most of the time as a geotechnologist,
we are interested in oxides of silica and
alumina and iron and you know magnesium and
sodium and potassium and so on.
And this is what is analysed by using XRD
analysis, I will talk about the x-ray diffraction
analysis, so most of the silicates, aluminates,
metallic oxides, carbonates, sulphates, nitrates
and phosphates which we are using these days
in the name of fertilizers or discharges which
are coming out of the industries are a good
example of oxygen cycle, alright.
So, these materials or the metals got oxygenated,
oxidized and hence these oxides are formed.
The second thing is nitrogen cycle, so nitrogen
is also an element which is useful for the
survival of flora and fauna, so this is how
we talk about the transfer of nitrogen between
the atmosphere, biosphere, lithosphere and
hydrosphere in different forms, alright. So,
we use the examples of nitrogen fixation alright.
You must have talked about eutrophication
of the lakes and the water bodies, then comes
the carbon cycle, so oxidation of the carbon
which is present in the material, so carbon
dioxide formation and this requires photosynthesis,
so this is the natural cycle and I hope you
can realize that as a geotechnologist, environmental
geotechnologist, we try to utilize these cycles
in a better manner, alright.
Just as a refresher, I thought I will just
discuss these things with you now, if you
take the man-made environment, this is quite
alarming. So, first of all this is the picture
you know a dire contrast against what I showed
to you some time back, litter, litter everywhere
and this is how most of the cities can be
defined right now you know, in the heart of
the cities, you will have a landfills and
landfills are the place where the people survive
and so on.
So, what are the components of the man-made
environment you normally, talk about the solid
phase and the liquid phase alright, gaseous
phase as I said we normally, do not consider
in our subject and this is something which
we live for the environmental scientists or
maybe the second logic could be whatever goes
in the gaseous phase will come back you know,
once the precipitation occurs, not a bad idea.
So, this is the list of you know man-made
environment, we have different types of agricultural
waste, agriculture was supposed to be a very
neat and clean activity but no more because
of the dumping of lot of you know manure or
the fertilizers, we are over fertilizing the
land, we discussed this some time back you
know and what are the social consequences
alright, this is shown very well depicted
in some of the movies that nobody is interested
in agricultural practices.
And hence what is happening in this whole,
here is a disorder in the society, so any
type of agricultural remains create man-made
environment, human and animal waste I think
I gave you ample examples of bio solids, the
sludges which are coming out of different
treatment plants, water treatment plant, sludge
treatment plant and I think I cited these
examples that the big question is if you do
not clean up your lagoons or the septic tanks
or the water holding ponds or sewage holding
ponds you know, you cannot sustain the processes,
sustain the society.
So, sewage has to be treated, water has to
be treated and these are the places where
the sediments which get deposited in the lagoons
or in the ponds are having pathogenic activity,
microbial activity, bacterial activity alright.
So, the question is if I have to clean up
these lagoon's or the ponds, how and where
I should dispose the sediments? So, this becomes
a man-made system.
I think, I cited one example and one of my
PhD scholars also worked on this topic, Dr.
Susmita Sharma, she is presently a faculty
member at NIT Meghalaya, so we coined this
term as SEGS; socio-economically generated
sediments alright, something interesting which
flashed in our mind, then let us talk about
SEGS; SEGS that is socio economically generated
sediments.
So, every country because of its social economical
condition produces the sediments, clear and
now the big question is where to dispose then,
similarly another example would be biosolids
so, biosolids see, again the question is they
are pathogenic in a; so another issue is you
know the biosolids where you are going to
dispose them, how you are going to handle,
so I think I asked you to search on the Google
also what is being done with the bio solids
particularly in countries like Australia and
India, we do not have any clues.
And again, these are the sediments which are
to be handled by geotechnical engineers, environmental
geotechnologies. “Professor – student
conversation starts” like, if you go to
an STP like today sir, they have like all
the facilities to treat the sludge and this
biosolids, they make like anaerobic, like
anaerobic processes they do to dewater the
sludge and then they make cakes out of it
and sell it to people that I have.
Everything is confined to the books, the fact
is this and the treatment also; aerobic, anaerobic
treatment also requires time, do you think
that in our society we have so much time to
wait for anything to happen, imagine the tons
and the millions of tons of the discharge
which is being done every hour alright. So,
the ground realities are different, you should;
if you are very serious you should be looking
on the net what is happening with these materials.
And why they are becoming a big issue, so
animal waste is also becoming a very big problem
particularly, related to the agricultural
sectors particularly, the animal Karakas,
you know after they die what to do with the
dead bodies in flash floods particularly,
there was a situation like this which happened
in Bombay a few years back, I hope you are
aware of this and then the biggest issue was
that the lot of animals died and what to do
with their Karakas.
“Professor – student conversation ends”
then, of course industrial waste which will
be handling separately because this is beyond
imagination and the volumes are so big that
cannot be discussing just as a passing remarks
so, we will be talking about this separately.
Mine waste; you must have heard about the
acid mine drainage on which Jasmine is working.
So, the acids which comes out of the coal
mines and the type of hazard which it creates
and the reason is known that most of the time
the coal has Fe2S, sorry, FeS2, iron sulphide
and this gets converted to H2So4 or this could
be pyrite also so, these 2 things might get
converted into acids and these acids drain
out and they form draining; acid draining
mines, a big problem, you cannot leave the
mines unattended.
“Professor – student conversation starts”
Is it possible to collect it and commercially
used that sir, well, you can but the biggest
question is most of these mines are in remote
areas, so that is what the first question
is whether people like you should be going
there or not, you know where the most of the
mining is being done in Kokrajhar district
of Assam so the volumes of the acids which
are getting discharged, how would you pack
them.
And concentration is a big question and then
purity, then the question is somebody has
to run an industry to maybe you know create
concentrated acids and then use them but again
the purity is going to be a big question alright,
your idea is good, so maybe you can think
of some start up and you try to convert acid
mine drains into acids, it can be of some
commercial application. “Professor – student
conversation ends.”
But we are trying to do is; we are trying
to marry the acids which come out of the mines
and we want to neutralize some industrial
waste by using this concept, so this is possible,
so that is the whole concept on which Ganaraj
is working and Jasmine is working, then comes
the nuclear waste of different types, I think
we have discussed a lot about this and I will
not touch upon this now much more.
Because except for citing some examples what
has been done by us in the past and to show
how you know guidelines can be developed by
scientists to safeguard the geoenvironment
against radionuclides impregnation and of
course, the construction effects; you know
blasting, when you do lot of destruction occurs,
tremors, micro tremors that produced you do
dewatering for different projects.
And the construction and demolition debris
are a very big issue, what to do with this,
city like Bombay how many multi-story buildings
we will be having and what is the life of
the concrete in city like Bombay you know
because of heavy chloride impregnation, so
this is the corrosivity of the concrete which
I am referring to and every 15th year the
building requires refurbishing.
So, the volumes of C and D waste which you
are creating or got forbid, if earthquake
comes and if buildings get uprooted alright.
So, how to handle the C and D waste, it is
a very big question now, these are the issues
which people never thought about earlier but
now I am sure that you know society is forcing
here to think like this.
