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Geotechnical and Mineralogical Characterization

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Video 1: Need for Geomaterial Characterization:
Until now in conventional geomechanics whatever you have studied is a part of the geometricalcharacterization.Mostly the characterization dealt with the geological characterization the way the soilsare form, genesis of formation, type of weathering, type of deposition, type of agencies whichare responsible for formation of science.Then you use different types of classification schemes to understand the behavior of thematerial USCS, ISSCS, AASHTO, USBR.These are the techniques to characterize the geomaterials.Then you also talked about the mineralogical characterization but not in full and chemicalcharacterization conventional geomechanics does not deal with much and of course themorphological characterization is not done much under the realm of conventional geomechanics.But of course, compressibility, compatibility, consolidation characteristics, and ultimatelythe shear strength characteristics.These are all different types of characterization schemes which are utilized to characterizegeomaterials.So, in this context if you really want to study the holistic characterization schemeor the plan of action we have already talked about the need for geomaterial characterization.First being a geotechnical engineer our emphasis would be to understand how geomaterials shouldbe characterized for their geotechnical characteristics followed by the mineralogy.Because the geotechnical characteristics are heavily dependent upon the methodology ofgeomaterial followed by the morphology.Morphology is the granulometry also sometimes we talk about the particle shape, roundness,flakiness and regularity, irregularity and so on.Then we will be talking about the physical characterization schemes.What are the physics of the material?Because geotechnical properties will also depend upon the morphology and physical characteristicscould be same.And these 2 characteristics influence geotechnical properties quite a lot.Then we will have a prolonged discussion on chemical characterization of geomaterialswhere we will be talking about pore-solution sampling which is quite contemporary and thena corrosion potential of the soils, modern day infrastructure, and particularly the industrieswhich are conveying either a fluid or you know material in solid form.A good example would be conveyance of fly ash in the dry form in the pipelines.It could be in the wet form also; it could be in the dry form also.So, these pipelines are the you know lifeline of the nation and in conventional geotechnicalengineering we are not done much justice with the buried pipeline design.Apart from the mechanical load how these pipelines get corroded in the due course of time isa matter of great concern to most of the companies which are dealing with conveying anythingthrough the pipeline.The soil, oil, gas, solid, semi-solids, dredging industry and so on.We will talk about sorption-desorption from this point onwards that how these mechanismsare utilized to quantify the soil contaminant interaction.So, until now whatever I have been discussing was abstract.I have been only creating situations where the contaminants come in contact with geomaterialsand then the question all what happens then?Once you start dealing with the sorption-desorption mechanisms you can quantify this interaction.And once it has been quantified it can be utilized the way you want it to.Then we will be talking more thermal characterization of geomaterials.Next would be electrical characterization of geomaterials followed by magnetic characterizationof geomaterials and this would be followed by biological characterization of geomaterials.But as I said biological characterization is yet in a very nascent stage in geotechnicalengineering.So deliberately I am not going to deal much with the biological characterization and sameis the case with magnetic characterization also.So, I would not be dealing much in details and similarly the characterization of geomaterialsbased on the radiation.So, these 3 are I am not going to talk about in this course.These are very active research areas in which my students are working, and we are stilltrying to evolve various processes associated with this.You must have realized that when I have created this list of geomaterial characterizationmost of the emphasis is on how environmental energy field is going to influence the geomaterialsand a good example would be thermal, electrical, magnetic, biological, and radiation processesapart from the mechanical energy field which we talk about.So, you will be surprised to know that how much information has already been createdand this answers one of your question which you are asking sometime back that what isthe state of the characterization schemes?So, the foundations have already been well laid only thing is that stuffing has to bedone and make these methodologies which we have proposed and the type of instrumentationwhich we have created has to be more and more generalized alright.So, needs for geomaterial characterization has already been discussed in the previouslecture.And all physical, chemical, mineralogical, thermal, electrical, energy fields would alterthe properties of the geomaterials particularly geotechnical properties.So, this is what the big question mark is how to study these effects?How to quantify them?How to utilize them in day to day practice.So, you may say from this point onwards the R and D and you know most of the real-lifeproblems how they have been sold?They have been tackled by our group I am going to talk about.I think I also discussed about the THM model where you know how thermo-hydro-mechanicalcoupling is becoming a very important feature in geotechnical engineering, contemporarygeotechnical engineering.And I gave examples from atomic waste disposal and design of buffers.That is a good example of how the geotechnical aspects of the material would change, onceyou create a situation where the geomaterials interacts with aggressive environment andaggressive environment would be extremely high chemical concentrations, extremely highyou know thermal gradients, extremely high electrical gradients and so on.And I think I have also discussed about what is the importance of THMB and THMCB also.So, C is missing here.I think you should add here.This should be thermo-hydro-mechanical models.Next should be thermo-hydro-mechanical-chemical models THMC followed by thermo-hydro-mechanical-chemical-biologicalmodels THMCB.So, this is what the recent trend is and people are trying to work on add chemical part tothese models.So as far as geotechnical characterization is concerned you normally talk about the voidratio and porosity of the geomaterials you know how to compute them.Of course, there are latest developments in the field of even computing the void ratioand the porosity.And as I have been telling in the past that conventional equipments are not used for determiningthe void ratio and the porosity anymore.Because this is the era of instrumentation and particularly electronics.So, people want to measure all these things under in-situ conditions.Similarly, compaction also one of the days when people used to do compaction controlledby taking the you know course of the sample or by sand displacement.Look at the type of infrastructure which is being developed in the country right now youknow 2000 kilometers of the infrastructure is being developed every day.That is what the statistics are.So how many core samples you can take at what depth?So, this also has changed now to more of recent instrumentations where people are using differenttypes of probes, nuclear density probes, gauges, thermal probes and electrical probes to computethe initiative densities.Consolidation and compatibility is of great importance to the geotechnical engineers andthere are techniques by which people are measuring the initiative consolidation characteristicsand compressibility of the soils.This is where somewhere hydraulic conductivity also comes in the picture you know when youare designing the systems it is not the hydraulic connectivity but the conductivity of the fluxwhich I emphasize in one of the lectures is becoming more important.So hydraulic conductivity is the flux of water when it is flowing through the porous media.It could be thermal flux, it could be magnetic flux, it could be chemical flux, it couldbe radiation flux, it could be biological flux and so on.Shear strength parameters you know how to obtain further geomaterials and normally weconduct a triaxial test, shear box test and if we want to find out the in-situ characteristics,there are several types of tests like when shear and flat jack and you know what elseyou are aware of dilative meters are normally used to get the shear strength characteristics.There is something which is not normally covered in the conventional geomechanics is the collapsepotential of the soil.Particularly this subject becomes very important when you are dealing with the soils whichare sandy materials like in the middle east region where you have desserts and you cannotconduct shear strength test to obtain the shear strength parameters.In our country also now most of the infrastructure is being developed in the Western part ofthe country.A lot of oil exploration is going on in the dessert area and 9, 10 big oil fields havebeen established you should read in google and try to understand what are the challengesthese oil companies are facing when they have to do infrastructure design on soils whichare collapsible?So, what is meant by collapsible soils?Normally the instability cause in the wide ratios per unit volume is defined as the collapsepotential in percentages.So if you look at this graph normally what is done is you take an oedometer ring andin oedometer ring you pack the dry soil at a certain density granular soils not the cohesivesoils and then at a certain stress where you are interested in finding out how much thematerial would collapse in terms of its voids you inundated.So as if I am trying to stimulate something which is happening in the nature.You imagine there is a heap of industrial by products which is lying, and lot of thesudden rains come.So, this is what actually we are getting in the laboratory.How much structural collapse of this type of heaps is going to occur?This could be municipal solid waste also where people are interested in.So, sigma prime would be the effective stress at which the inundation is done and becauseof flooding or because of interaction of the geomaterial with water how much void ratiohas change?This is the collapse.So, people who are working in dessert areas they utilize this scheme for dealing withtheir design and you know execution of the projects.So e0 is the initial void ratio and ef is the final void ratio at a given sigma primeand 1+e0 is the you know unit volume of the soils.You must have studied in geomechanics.So, because we are dealing with the industrial by products quite a lot we have to deal withthe collapse potential based classification scheme.

Video 2: Mineralogical Characterization
The second in the series is the mineralogical characterization.Normally XRD is done for mineralogical characterization of geomaterials and nowadays you have veryadvanced tools which are used for obtaining the x-ray diffraction patterns of the geomaterials.So, these are the types of machines which we have in IIT, Bombay and several other institutes.Government of India has created advanced instrumentation facilities which we call as SAIF sophisticatedand advanced instrumentation facility which is created by DST at the five locations inthe country.The region was that it is a regional facility where people can do advanced testing of thegeomaterials.So, most of our results depends heavily on the facility with SAIF provides.So essentially what is done is?You take a sample and you know bombard this sample with the x-rays and then record thediffraction pattern.So, I will show you how the analysis is done.The second in the series is scanning electron microscopy.I will also show you today how scanning electron microscopy is done to realize the orientationof the grains which you might have studied only in the books.But you might not ever realize that how the real-life pictures look like?So, by using XRD and SEM we can find out the mineralogical characteristics of the geomaterials.Sometimes these could be EDX.So, we can have the you know diffraction pattern at the same time and I am seeing the environmentalscanning of the material depending upon the requirements.This is how the results look like.So, if you look at the XRD analysis.These are known as XRD diffractograms.I can utilize this information in several manners.First of all, as a civil engineer I would like to use the inert materials in the foundationsystems.I do not want to use a material which is very active alright chemically or physically Iwould not say.So XRD is a technique where I take some sample and by using the Bragg’s law if you remember2d sin theta = n lambda in your physics course you must have studied 10 plus 2 or maybe lateron in the engineering.So if I know the lambda is the wavelength of the wave which I am using to bombard onthe sample I can find out the d and d happens to be the intermolecular spacing of the atomsor the lattice structure what we call as.So, you must have studied the lattice structure of the crystal a, b, c alright.So, these things are becoming very prominent nowadays.So, if you look at one of the diffractograms on the Y axis we have relative intensity andon the X axis we have copper K alpha is a filter through which the X rays are channelizedmonochromatic you must have studied in your physics courses how to create a light in themonochromatic form?And then so this happens to be the 2 times theta where theta is the angle of incidenceof the waves.So, if you can fix theta and if you know the wavelength of the ray which you are usingyou can compute d. 2d sin theta = n lambda is the Braggs law.Now corresponding to 2 theta value we get different peaks of the minerals.So simply by looking at the XRD patterns I can make out whether the material is activeor inert.So, the thumb rule says the more and more peaks you have in the material, this materialis going to be crystalline clear.A crystalline material would not react on its own unless you do some chemical treatmentor unless you pulverize it alright.We were talking about ultra-high active fly ashes, ultra-fine fly ashes you know and thisis what I told you that either you can use a classifier to separate different particlesand of different densities and different shapes or what you can do is?You can apply different type of fields.It could be airfield; it could be density separation by putting the electromagneticelectric field or whatever electromagnetic fields.So, these other techniques that people are practicing and the more and more peaks youget the material is bound to be crystalline inert material, good material to be utilizedfor creating foundations, fillings, reclamation alright.But if you have a material like this where you do not have distinct peaks.The story is different.So, what this indicates is that this material is going to be a highly reactive materialand we call this material as a material which has lot of glassy phase in this glass.So, if you take cement and if you do the XRD you will get something of this art.There is no distinct peak over here.So, and lot of hazy XRD pattern shows that this material is having potential to be agood pozzolanic material.Because when you have more glass present in the system, the system becomes reactive alright.So, this is one of the ways to differentiate between the activity of the material activeand passive minerals.So in any walk of life if you are a hard core geotechnical engineer or you are a materialscientist working in the field of cement and concrete technology or design of resins, filters,different types of you know catalysts you will have to depend upon this.You know this also gives me an opportunity to interact with people from different departmentsand different streams because our interests are common.I just want to characterize the material.So nowadays world has changed earlier we used to sit down and up to the fourth decimal placeof theta value we used to match the minerals in present in the soil and this has to bevery tedious also.Earlier students of mine they have spent 3, 3, 4, 4 months altogether characterizing onesoil.Can you believe this nowadays it is a matter of few hours?So, we have these types of soft wares which are known as JCPDS files you know there isa powder diffraction file.There is a CD ROM.And sometimes people use ICSD inorganic crystal structure database.The results are listed over here.So, for different types of soils.What you observe is that mineralogical composition in a qualitative manner can be opted alright.And since Dr. Susha’s thesis we started getting the quantitative mineralogical phasesalso.So, this is something one stage ahead of what is happening in todays world our lab has beenquite active and we are much ahead of what the practices are in the market right now.So I can do the you know qualitative analysis of the phase of the minerals and there aresoft wares which are available and known as expert high score, EXPERT high score.So if you get time just google it and you will realize how these type of soft waresare being used to quantify the mineralogical phases.The question is where I am going to use all this information.We have been talking about application of geomaterials in buffers for the radioactiveas disposal.This is a very interesting and practical problem but multi-phase problem.The structural stability of the material should be good number 1.At the same time chemical affinity and the reactivity of the material should also beextremely high.So this is a system when you are dealing with nuclear waste disposal.The material is supposed to be at the mechanical loads, thermal loads, chemical loads, biologicalloads, and radiological loads.Now I think you understand where these types of studies are being done.And this is where you have to select minerals also.So gone are the days when naturally occurring minerals is to be used in the industry.Because nowadays people are you know they are very demanding.So every nation has its own demand for creation of a mineral of a certain specific value forvarious applications.So suppose there is a breach of atomic power plant and most of the atomic activity comesin the water in the sea.Because most of the establishment are on the seashores.The chances are the entire seabed or the sands on the shore may get contaminated.It is a very practical problem for which you have contacted sometime back by from by acountry.And they wanted us to create minerals of a certain specific value.We will be talking about this later on.So these are the things which are happening in the realm of geotechnical engineering Iam sure you must be finding it a big story but this is what is being done.So if you click on this you will find that there is a information which is availableon the website about ISCDS.You know this is what is the need of the hour.So good geotechnical engineering can only be done once you start from the mineralogicalcharacterization of soils or the minerals.This show how the lattice also can be quantified.So you can just go through this site and try to learn what are the facilities which areavailable in todays world.I hope you can realize that when people join my group it becomes for them a challenge tocope up with what has already and what is being done.Because our expectations are extremely high good from the people.But unless expectations are high things cannot be done.This is the first thing people are supposed to learn.If I quickly analyze this data which is present in the table you will find that most of thegeomaterials would have quartz alright, illite, kaolinite, calcite, feldspar, hematite.So, hematite is the one which is mostly present in the fly ashes.It comes as an impurity in the coal.RSS is the red sandstone and BSS is the brown sandstone from different parts of the worldwe collected this.IC is the chalk sample which I got from Israel.Because Israeli chalk has very high porosity and their aquifers are mostly chalk basedaquifers.What different projects are being studying the formations from different continents andC1 and C2 are the cenospheres which you separate out from the fly ash by different techniques.So classifiers which I have talked about is one of the ways you can do density separation.You can do filtration from the lagoons.These are all subjects where lot of entrepreneurship is being done by young guys.And for your information the cenospheres are the pure quartz.They can be utilized for substitution for pure silica in the electronic industry.So if you check it on net you will find at least there are 350 applications of cenosphereswhich are in the market right now alright.These are the subjects which are picking up at the moment alright.So one of the most challenging task which I think I may give it to you is suppose ifthese are the materials which are naturally occurring and if I ask you to use filter outa certain type of mineral and sell it in the market.And it is something very interesting, very commercial you know question that from thesoil which is laying here and there.How can I produce a mineral?And people are working on it.