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Soil: A living Entity

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Video 1: Basics of Soil
Today’s discussion is now having discussed all these things, you must have realised that,soils are no more an inert material, they are not a dead material, lot of things arehappening inside, the moment bacteria comes, it becomes a dynamic system, for human beingbeings we will say know, your career is a function of time and the place where you wouldbe, will be in a different continent, after 2022, you will be flourishing or you willbe doing something, clear.Soils are also like that, I emphasised most of the time that the properties of scienceare a function of x, y, z and t and the best example I gave you, so truly speaking, scienceare living entities, they are not dead entities, we have treated them always like a dead materials,so you bring soil from the lab from the field pulverise it, put in the oven 100 degree centigrade,bake it, you have remove lot of things which were present and which contribute to the propertiesof the soils.So, you filter them out for the sake of your convenience, so whatever practice of engineeringyou are doing is only partial, it is not full, so soil is a living entity and hence it isquite susceptible and sensitive to the environment in which stays.We call about; we talk about sensitive soils, is it not, we have given you; I have talkedabout several examples where how the environment is influencing the characteristics of thesoils, you change the pressure temperature conditions, depressurisation occurs somethingstarts leaking out of it, human body, clear.Emotions; something changes, something says something and look at this your pore pressureis starts dissipating through your eyes, so all similar.So, environmental influence is very, very important, we will talk about this, just likehuman and living beings, you know and then of course, I like saying this that there islot of heritage, parentage, linkage, genetics, memory, emotions and response to externalstimulus which we have to take into account.If you want to do contemporary geomechanics, it is so unfortunate that most of the timewe do not bother about all these things, for us soil is an inert material, it is not so,clear.So, now ultimately this answer comes from the rock cycle, the way you are found, theway the soil was found.So, heritage; heritage, parentage is nothing but the way you are formed in which familyyou took birth, all the bank account goes in your name, clear by virtue of taking birthin that family.Linkage; the linkage is between your parents off springs, rocks, soils, mineralogy is same,only the composition of the minerals is different because of the formation or the recreationof the soils.Genetics; we talk about genetics also, we talk about memory effect in geotechnical engineering,the statistics, loading, unloading, you know you do one loading, load versus sediment curveand reloaded, what happened; that point of over consolidation remains unique point, correct.So, you do number of cycles of consolidation plate load test what happens; material remembersthat it has behaved like NC, OC, again it becomes NC, so beyond this pressure, it hasto behave like normally consolidated, clear, now this is the memory effect, it remainsin the memory of the material how it has to behave.Exposure to certain stresses and the material recognises it immediately, I should behavelike normally consolidate, not like OC behaviour, is this correct.Emotions; I just give an example what emotions are, I will say something to you harsh, youstart crying dissipation of emotions, clear.We have several examples; consolidation is the good example of this, we will talk aboutthis.As a same time, I say something very good, you feel elated, joyous, face glows, emotionsthat will reflected on your face, is it not?Swelling and shrinking behaviour would be one of this, you can look at it like this.Responses to external stimulus that is what actually we are trying to study, so we aretrying to create a matrix of all these traits which are similar to human body, so for us,the environmental geomechanics, one of the important things is that we should treat thismaterial as a living material, clear, we should not say that this is a bad material, thereis no life in it, it is not so, leave marine clays for certain time what do happen?They decay.This question I asked in the very first lecture and you are trying to answer that despitethe best possible sampling, despite the best possible testing, despite the best possiblesoftware’s, which we can think of why our systems are failing; this is the answer nowwe are getting today, hope you remember the question, which we discussed sometime back,so everything is best possible; the best possible sampling, very understood sample you havetaken, you got the best possible parameters clear, best possible computer course we areusing to get the answers to a questions.But is still when the systems are in place they fail, why?Because the properties are time dependent which you did not take into the account, theydecay, they may become better also, they get upgraded also, microbial activity, so thisis the issue which we have completely ignored but in real life, you will observe that theseactivities are playing a very, very important role, unless you include them, things arenot going to happen properly.And that is what calls the new era geomechanics you know the environment, the soil is notgoing to interact with the pure water which we use in the laboratory, you are interestedin solving the problem, where the landfill leachates are getting intruded into the foundationsand they are trying to heat up the foundations, clear.So, these are the situation which we have to study, is this part clear.So, when we talk about all this, you know this thing I enjoy a talking to my PG students,are you must have heard about Panchatantra’s the 5 elements of life which we; which createthe life in you language, you must be using different language and different terms todefine this, so Panch Tatvas is the the elements and Jeevan is life’s, so you know Kshitij,it is horizon, Gagan is sky, Pavak is fire, Jal is water and Sameer is Air.Interplay of all these 5 elements creates the entire geomechanics that is very interesting,is it not?When you are kids, you are taught all these things, when we have become professional,we have forgot all these things, that is the only thing we are unable to handle the situationproperly.So, what this first 2 elements do, any guess?Infinity, the first assumption in all your models is semi-infinite soil mass, whetherit is Rankine, whether it is Boussinesq.So, you have cut across the 2 the entire hemisphere, you said the bottom portion I am only interestedin not the top portion which is the atmosphere environmental scientist will take care of,so you say semi-infinite, beneath the ground only you are consider that is the domain inwhich you work.Horizon and sky; sky is nothing but the environmental conditions; weathering conditions, you rememberwhere they get deposited, horizons.So, soils after disintegration after weathering, they get deposited somewhere, alright, nowwhat happens with sky and fire?This is the formation of the soil; environmental conditions at elevated temperatures, disintegrationof the rocks, formation of soil, clear and this formation of the soil is taking placein the semi-infinite domain.Now, if I consider water and air, these are the transportation agencies; deposition andtransportation agencies.So, I like this philosophy, now, if you start looking at the material with which you aredealing that is the soils and if you know the genesis of the material now, your anglechanges, perception changes looking at the things the way you do is changing, correct.So, you think of a totality now, so if this is a situation you know what happens; we havedefined soils in different physical terms, physical only, you know these are all physicalterms, particle size nothing more than that.So, most of the geomechanics which you study is blend of anything which is beyond physicsof the matter, we do not give much value to the chemistry, mineralogy, biology, bioticactivity and so on.The whole classification system is based on particle size, so Boulders, cobbles, gravels,sand, clays, slit, clay, organic matter based on particle size.One interesting thing in the philosophical thing is the way the size decreases, whathappens with the activity of the material; it enhances, correct, so this is how the experiences;the more and more experience you are, the more and more refined you becomes, clear,you become.And then what happens, the activity increases, percent become more productive, it is so unfortunatethat we do not talk anything about organic matter much in geomechanics, why?All your tests are related and are valid until 2 microns, stokes law, less than that is the,what form of the material; colloids and colloids are the one which control the properties offined grain materials maximum.I think we are having this discussion sometime back, so you will realise that the role ofthe organic matter and colloids is so much, it governs almost 99% of the properties ofthe fine grain material but we unfortunately, ignore it, why?Because we do not have tools to characterise it, it is so sad, are you realise it, thelimitations are there and the logic given to the limitations is do not consider them,this is not correct.So, modern-day geo mechanics concentrate mostly on less than 2-micron fraction why?Because this material is the most notorious, most active and most creative material thatcreates what you want to, you are getting this point so, this is a very interestingfact and you will realise that because of the limitations of detection of a certainphase, we are ignored it completely, are you getting this point.

Video 2: Soil Behaviour and Challenges
So, look at few symptoms, I am just trying to draw a relationship between you know, thehuman body and the soils with which you are working, rocks we are not working remember,because as I said that they are the parents, the chances of they are getting contaminated,adulterated, delineated, clear, affected are less, as compared to the off springs whichare in nascent, young, might get affected more, clear.So, we are trying to draw a relationship between or understanding between you know soils andthe human body because once you understand human body, then soils can be mastered better,most of the tools are same by the way, so soil is the particle material, all of youknow, and still it is much more complex than steel; steel is made by human beings correct.So, between us and soil is what; steel, because we created steel, rocks are naturally occurring,standard material created by nature, a standard material created by human beings is steel.Then human beings and soils, it is a 4-phase system, now you try to see what happens.So, most of the time you must have realise the properties of soils depend upon soil type,we always say what is the soil type, size of the grains, shape of the grains, what arethe minerals which are present in it, agreed, then we talk about what is the second thingwhich we are going to talk about; water content, air content, degree of saturation.The way you divide the studies is conventional geomechanics 2 phase system, unconventionalunsaturated soil mechanics 3 phase system and today, I introduce in the lecture, multiphasesystem.Electrochemical effects; we will be talking about them, climatic effects; I think I havegiven you enough indication about how humidity, temperature pressure, permafrost conditionsinfluence the properties of the soils.Stress history; this is what you are discussing sometime back, memory effect, so soil understandswhat is the OCR, what is the UCR, what is the NC material and what is the precursorsand pressure so, look at the response less than pre-consolidation pressure, it is OCmaterial, more than the pre-consolidation pressure, it is NC material, you keep on repeatingthe loading, unloading, what happens; the NC behaviour becomes almost uniform, clear,it is a continuous curve, whatever perturbations have happened in between, they become a loop,hysteresis I was talking about.And that goes into the memory of the system that it has been exposed to this much pressurein the past, still in my opinion, predicting soil response is easier than predicting humanbeings’ response, why?Human beings’ area much more complicated, but what do we do; we try to understand theresponse of soils in accelerated environment, decelerated environment, extreme environmentalconditions and so on.Why?Because these type of condition exist somewhere, so the main emphasis of an environmental geomechanicsis to simulate all these things and the logic is soils are more workable, you know thanthe living beings and living beings have come out of the soils., so this is the completelogic.Look at the symptoms which are common between human beings and soil, just to make sure thatwhat we are discussing at lot of similarity, you know obesity.People like us; me, particularly, what is this anorexia, then we talk about high bloodpressure, most of us suffering with that, then we have giddiness, agreed, then we haveepilepsy, then we have fractures, then we have fatigue and the last but not the leastis urinary problems.A geotechnical engineers deals with all of these issues in particular, the last one muchmore, seepage problems, everywhere so, obesity is expansive behaviour of the soil, you eattoo much, you absorb too much water soil, anorexia, shrinkage, clear, instability, highblood pressure over a pressure, then we have giddiness, instability of the system, epilepsy;liquefaction, loss of sense, so adequate start boiling.Fractures; failure, is it not?Failures of different types, collapse of the foundation, retaining walls, a structure whichwe are making on the system, what is fatigue; cyclic loading, so keep on doing cyclic loading550,000, 10,000, 1 lakh, this is all you design your payments, you want to see what is theresilient modulus of the system, when it collapses, clear and urinary problem which I have alreadyI talked about, drainage conditions, for us it is very, very important, otherwise everythingwill be in a less.Look at the bodies of the dams, we design filters, drainage conditions and so on, sowhat are the challenges and the concerns which we are facing in a professional, any idea?The bottom line of the whole discussion today is that I cited few examples, there I wastrying to show you that systems with which we are dealing, soils is live number 1 andwhen we understand the human body better in today's world, you know medicine and surgeryhas advanced quite a lot.But not our subject, our subject has not advanced so much, is still we are talking about theold concepts, so there are challenges, there are concerns, how to first of all change thesubject itself, how to lay the foundations of new concepts and some of the new conceptsI have discussed in today’s lecture.So, what geotechnical engineering professionals should be involved with; what they shouldbe doing?Three things; diagnostics, so look at your soil mechanics course, the way it is taught,first 5 lectures are only testing, you know classification, how soils got formed, howthey were depositing, residual soils are like this, transported soils are like this, finedgrained soils are like this, coarse grained soils are like this, 100’s of tests aredone to characterise them, even the shear strength theory is also diagnostics underthe action of a normal stress, confining stress and shearing, how the material will goingto behave?So, when we say NC, OC behaviour, we forget about the material, whether it is sand orclay, we do not bother, we simply talk in terms of state of stress, it is in materialwhether we are dealing with the sands or we are dealing with the clays, so diagnosticsis very important like medicine, medical sciences, most of the efforts are being made by geotechnicalengineers particularly, environmental geomechanics guys to understand the material.Symptoms and abnormalities; your profession is mostly go to the site to try to understandwhat is happening and unfortunately, we would not find any of these things written in thebooks because subject is young, the type of pollution which you are producing from yourindustry might not be similar to the one which has been produced anywhere in the world.So, the interaction with this system is going to have with the soils and the rock is goingto be absolutely different as compared to the one, which I ever been studied.So, this becomes more of a case study type of subject, evidence based, are you gettinga feel of this; so take each case as the way a medical practitioner takes a human body,each patient is different, the medicine which might work on me will not work on you, weare different in constitution.So, here most of the effort is on understanding the symptoms and the abnormalities and onceyou have understood this, and this is diagnostics for which there are several tests, we willspend lot of time studying the geomaterial characterisation.I will spend lot of time in making you understand how physical characterisation is done, howchemical characterisation is done, how mineralogical characterisation is done, how biological characterisationis done, how thermal characterisation is done, how electrical characterisation is done, howmagnetic characterisation is done of the soils.So, this is going to be very intricate and then once I have done the diagnostics characterisation,I have understood the problem a bit.I will start treating the material clear, after diagnostics what medical practitionersdo; they prescribed you something, they write down prescription, so take this, this medicineand see me after 2 weeks, 3 weeks, 1 month, clear and slowly, and slowly it tapers downmedicine also, so first is adequate correction and then comes prolonged monitoring, followup, patient is very serious putting him or have in ICU, so we want to monitor, you wantto see how effective the prescription is.So, most of the techniques which are used now a days in geotechnical engineering aremonitoring and monitoring is done with the help of either satellites or with the helpof sensors or with the help of electronic gadgets, it could be x-ray based, it is couldbe SEM based whatever, we will discuss all these things quite in details, alright.