 Welcome to advanced geotechnical engineering course which is being offered under the program of NPTEL phase 2 being developed at IIT Bombay. So as you all know the soil mechanics are part of geotechnical engineering plays an important role in the behavior of civil engineering structures. So this course is being offered for graduate students as well as for practicing engineers who are actually going to use or work in the area of geotechnical engineering. Myself Professor BVS Vishwanatham, I am professor at department of civil engineering with geotechnical engineering as specialization. My research areas include centrifuge modeling of geotechnical structures, research in geotechnical engineering, soil reinforcement, geosynthetics and details of my work can be seen at website www civil.iatp.ac.in backslash tilde Vishwanatham. My email ID is given here Vishwanatham at the rate civil.iatp.ac.in. So this course we would like to cover in the following heads. First we will introduce ourselves to origin and nature of the soils as engineering materials. As you all know soil and rocks are the major engineering materials which are used in civil engineering construction. And then we will try to classify the soils and try to look into the clay mineralogical aspects. Thereafter soil compaction, soil water interaction, permeability and seepage and effective stress will be covered. After this consolidation behavior of the soil and methods for accelerating consolidation of the soil will be introduced. Having done this the stress strain strength response of soils will be discussed in depth and as an application to this earth retaining structures and stability analysis of slopes will be covered. This is followed by buried structures and their behavior and this course will be given a closure with geotechnical physical modeling. This course is covered in 8 modules. In module 1 soil composition and soil structure will be covered. After the soil composition and soil structure we will be looking into soil formation, types of soils and their characteristics, particle sizes and shapes, their impact on engineering properties, soil structure, clay mineralogy, soil water interaction, consistency, soil compaction and concept of effective stress will be introduced here in this module. At each module we will be actually having problems and also self-evaluation and tutorial problems so that this will bring close to the subject what you learnt in the previous lectures which are actually there in this module. As a second module we will be covering permeability and seepage, permeability and seepage force and effective stress during seepage. Laplace equations of flow particularly fluid flow in soil in one dimensional, two dimensional and three dimensional seepage, flow nets, aniostropic and nanomersenous medium confined and unconfined seepage and along with practical examples will be discussed in this module. In module 3 the compressibility and consolidation and under this the stresses in soil from surface loads, Terzaghi's one dimensional consolidation theory, application in different boundary conditions, ramp loading that is the loading which is actually carried out happens in the field, determination of coefficient of consolidation, CV for normally and over consolidated soils along with some practical examples, compression curves, secondary consolidation, radial consolidation and the settlement of compressible soil layers and methods for accelerating consolidation settlements will be discussed in this module 3. In module 4 stress strain relationship and the shear strength of soils will be discussed. In this module we will be discussing stress state, Mohr's circle analysis and pole principle stress in the space and stress paths in PQ space, Mohr Coulomb failure criteria and its limitations, correlation with the PQ space and stress strain behavior, isotropic compression and pressure dependency, confined compression, large stress compression, definition of failure, interlocking concept and its interpretations, drainage conditions and traction behavior of stress state and analysis of unconfined, unconsolidated, undrained, consolidated, undrained, consolidated drain and other special tests, stress paths in traction and octahedral plane elastic modulus from the traction test will be introduced. So in this at the end of this module what we will do is that we will try to see number of problems and we will also try to have some tutorial problems. So this will actually allow you to understand in a better manner in this module. As module 5 and 6 as an application of shear strength what we learnt in module 4 what we do is that we will try to learn earth retaining structures in this earth pressures, stress changes in soil near retaining walls, earth pressures and pressure, estimation of earth pressure under drained and undrained loading and stability of slopes particularly stability analysis of a slope and final critical slip surface, sudden drawdown conditions and effective stress and total stress analysis, seismic displacements and marginally stable slopes and we will be introducing briefly to reliability based design of slopes and methods for enhancing stability of unstable slopes. There are many methods so that we can actually discuss some important methods so that how a stability of an unstable slope can be improved. In module 7 we will try to understand about the buried structures. These are very prominent or important nowadays with urban constructions. The load on pipes, Marston's load theory for rigid and flexible pipes, trench and projection conditions and minimum cover pipe flotation and liquefaction. So these are some of the critical conditions like liquefaction and then behavior of the pipes subjected to flotation and all will be discussed. Finally under 8th module we will be discussing geotechnical physical modeling, the physical modeling methods, applications of centrifuge modeling and its relevance to geotechnical engineering, centrifuge modeling of geotechnical structures with practical examples will be discussed. So if you look into this, the geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of ad materials. Geotechnical engineering uses principles of soil mechanics and rock mechanics. So here is the soil mechanics and rock mechanics to investigate subsurface conditions and materials which is very very important. So if you look the soil mechanics is the branch of science that deals with the study of physical properties of soil and the behavior of soil mass subjected to various types of forces. Whereas the rock mechanics is the theoretical and applied science of the mechanical behavior of rock and rock masses. So soil mechanics is the branch of science that deals with the study of the properties of the physical properties of soil and the behavior of soil mass subjected to various types of forces. The forces can be gravity forces or seepage forces or external loading etc. The rock mechanics is the theoretical and applied science of the mechanical behavior of rock and rock masses. So in this slide a series of geotechnical engineering construction activities which are actually formed with soil is shown. A natural slope or natural slope which is a geotechnical structure which is actually formed either because of the erosion or because of the gravity loading. So this natural slope which is actually shown and then in order to allow the urban construction sometimes along the hilly terrains the cut and fill method is adopted the slopes will be cut and then allowed for the slopes to the roads to construct. So this infrastructure development makes some of the existing natural slopes unstable. So hence there is a need for understanding about the behavior of these slopes under the natural conditions are subjected to some adverse effects. Here whenever if there is a requirement of storage of water then this particular structure is called embankment dam and which is required to prevent the leakage of the water through the dam. So this particular structure which is actually called as an embankment dam. So if you see here this particular structure is a building foundation for a 1 or 2 stories building. So here the foundation transmits the loads to the subsoil and it should be such that the settlement should be minimum. In this slide when the slope is steeper and if it is required then there is a need for the supporting. So if this is called a supported excavation or if you are using a braces for this it is called braces excavation or supported excavation. And in this case the next structure which is actually shown is a tunnel and which is required nowadays because of the urban constructions. So for the metros and other applications you need to have the underground constructions. So this particular cross section shows tunnel which is embedded in soil or it can be in the rock. So this is lining of the tunnel material and here in this particular figure part of the figure of this slide it shows buried pipe and which we will be discussing in the subsequent lectures. So this is a buried pipe at a certain depth below the ground level. And here in this particular figure it shows a road embankment above the existing ground level. So this is a typical structure which is very common as far as civil engineering construction for highway and railway applications is concerned. In particularly if you have got a soft soil and if there is a requirement of the large loads to be transferred to the deeper stratas then it is required to construct foundations such that the loads are actually transferred to the harder stratas which are actually there below. So here this is a cross section which actually shows the building on the pile foundation. So these yellow members which are actually shown are the piles and here this particular surrounding soil which may be can offer a frictional resistance or sometimes if it is in the form of a clay it derives the strength only from the bearing. So in this particular cross section what you see is geosynthetic reinforced soil walls which are actually very popular in urban construction nowadays because of the requirement of the construction of the steep walls in urban areas and where you can actually have different slip roads and highway intersections in the congested areas. So this is possible to construct with economical construction so that this can lead to you know large economics in the civil engineering construction. In this particular slide the left cross section of the figure which actually shows an ash pond dam so this is actually a started dike where the ash is actually deposited once the ash this portion is filled then the second dike is constructed above the started dike and to have economics the compacted ash is actually used as a filler and then it is surrounded by a soil so that this can actually have less prone for erosion. And here so like this you know it can actually go up to 3 to 5 levels so the total height of the structure can go up to 20-25 meters so this requires you know the understanding about the stability of this type of ash dams and also in retaining these ash safely. And because of the development and generation of the municipal solid waste there is a requirement for municipal solid waste landfills that means that the waste which is actually incinerated or generated has to be finally dumped safely in the ground or above the ground and this construction or this type of a geotechnical structure is called landfill. If the leachate which is actually generated is recirculated and from periodically so that this can actually avoid periodic treatment of the this can avoid intermittent treatment of the leachate so this is actually if that is the case then it is called bioreactile landfill. The recirculation of leachate allows the landfill to undergo decomposition rapidly and this can actually lead to the you know this particular areas can release for the future constructions. So in this slide a typical structure of construction on soft soil is shown so this is a typical oil storage tank which is actually constructed on soft soil and wherever it is close to the coastal belt there is a requirement there is a possibility that you have got soft soil. So in order to allow the construction that soft soil has to be consolidated so that the settlements are minimum. So here in this it involves construction on the soft soil particularly different techniques for accelerating the construction of the soft soil then this type of constructions can be made possible to have a better performance. So here this particular construction it shows a sea wall which actually protects the land from the waves which are actually arise because of the because of the waves which are arise because of the water which is actually there. So this is actually sea bed which also requires to understand about the stability that is from the stability point of view and these are windmill foundations which are actually these windmill foundations are nowadays used for production of the wind energy from the wind. So these are sometimes when they are located in the sea they are called they are located in offshore and sometimes they are also located on the onshore. So you have if you have got a windmill foundation which is there in the sea the typical foundation with the racker piles would look like this and this is a typical oil rig for a offshore foundation which is actually shown here on racker pile. So we have seen the different types of geotechnical structures and all these structures are subjected to typical failures for example if you have got a road which is on the soil which actually have inadequate drainage that can lead to if it is on the expansive soil the sub grade can undergo failure like this and if you have got a railway track on the soft soil formation there is a possibility of mud pumping like this and if you have got some instability because which is because of the sea page or because of some landslides then this or earthquake this type of instabilities can cause and if you have got a landfill and if the stability is not ensured either because of some mining work or some other problem then this type of landfill failure can cause and this is a close view of municipal solid waste which is in particular generated in Mumbai and which shown and this is the typical lead shade which is actually shown here. So the degree of contamination levels are very high and so if you wanted to see the impact on the engineering properties of the soil and all is required to be understood very clearly. So here the typical slope which is actually shown along the railway track and these type of failures are very common because of the sea page which actually takes place during the monsoon and here a typical railway track which is actually subjected to a track subsidence is shown. So geotechnical engineering if you look into the definition it is simply the branch of engineering that deals with structures built of or in natural soils and rocks. This subject requires knowledge of strength and stiffness of soils and rocks and methods of analysis of structures and hydraulics of groundwater flow. So you are required to understand the structures which are actually built of or in natural soils and rocks. So this subject requires knowledge of the strength and stiffness of soils and rocks, methods of analysis of structures and hydraulics of groundwater flow. So in this course we will be concentrating mostly on the soil behavior and soil stiffness and the methods of analysis of structures resting on the soil predominantly. As a course context I would like to introduce here an understanding of the engineering behavior of the ground and interaction between the ground and any structures built or in the ground is essential for civil engineers. So that means that this particular understanding about this subject which involves the engineering behavior of the ground and the interaction between the ground and any structure like retaining wall, interacting with the soil built on or on the ground is essential for civil engineers. Before introducing and giving references of this particular course I will be giving the quote which is actually given by Carl Tazaghi 1883 to 1963 who is known as the father of soil mechanics. Here it says like this, unfortunately soils are made by nature not by man. Many times in soil mechanics what will happen is that engineer requires to use the soils which are actually available in the nature. And the products of nature are always complex as soon as we pass from the steel and concrete to earth the omnipotence of the theory ceases to exist. Natural soil is never uniform we are going to see that there are different types of soils and its properties change from point to point while our knowledge of its properties are limited to those few spots at which the samples have been collected and tested. In soil mechanics the accuracy of computed results never exceeds that of a crude estimate and the principle function of theory consists in teaching us what and how to observe in the field. So here some selected references are listed in these are these references are listed in the alphabetical manner. Atkinson 2007 which will be following for majority of the portions of this course the mechanics of soils and foundations and which is published by Taylor and Francis in 2007 and this is the second edition which I included here. Eisen A 2005 soil mechanics the basic concepts and engineering applications Taylor and Francis London and which is published I think in the first edition and Craig 2004 this is the title of this book is Craig's soil mechanics spawn fresh Taylor and Francis London and New York 7th edition thus BM 2008 advanced soil mechanics Taylor and Francis London and New York 3rd edition. Fang and Daniels 2006 introductory geotechnical engineering and environmental perspective Taylor and Francis London and New York 1st edition. Fredlund and Rahatzo soil mechanics and for unsaturated soils John Willey and Sons New York 1st edition. Hols and Kovacs which we will be discussing basically for stress parts 1981 and introduction to geotechnical engineering Prentice Hall New Jersey. Kaniraj SR 2008 the mechanics of soils and foundations Tata McGrahill publishing company New Delhi 10th print, McCarthy 2007 essentials of soil mechanics and foundations basic geotechnics Prentice Hall New Jersey 7th edition, Parry RHG 2004 more circles stress parts and geotechnics. So here we will be discussing mostly about the stress parts and then the failure criteria which are actually involved with the stress stiffness response of soils and the spawn press Taylor and Francis and London and New York 2nd edition. Wood DM geotechnical modelling basically here we will be covering the geotechnical physical modelling involved which is in the module 8 of this course. So as a source of the soil first let us look into the origin of the rock and origin of the soils. So the rock the source of the soils most of the non-organic materials that are identified as soil originated from the rock as the parent material. As you all know that the rocks that form the earth surface are classified as to origin as igneous sedimentary and metamorphic rocks. Igneous rocks sedimentary rocks are metamorphic rocks. These igneous rocks are formed directly from the molten state of magma. The molten magma that cools rapidly at or near earth surface are called extrusive or volcanic type rocks. Examples for this are basalt, rheoloids and andesites. If the molten rock cools very slowly the different materials segregate into large crystals forming a coarse grained or granular structure that trapped in deep at deeper depths. Intrusive or plutonic type examples for this type of rock which is actually formed when the molten rock cools very slowly that is granite which consists of quartz and pels part, cyrites and gabros. Because of the isilka content these rocks are called as acidic rocks. They decompose to predominantly sandy or gravelly with little clay. So you see here when these rocks with isilka content when they decompose they form a predominantly sandy or gravelly with little clay. This is actually used as good construction material. Rocks whose minerals contain iron, magnesium, calcium or sodium but little silica such as the gabros, diabetes, basalt are called as basic rocks. The rocks whose minerals contain iron, magnesium or calcium or sodium but little amount of silica these rocks are called as basic rocks. Examples are gabros, basalt. And the solution of the magma is cooled very very rapidly. The minerals do not separate into crystals but solidify as amorphous vitreous rocks such as examples volcanic scoria, pumice and obsidian. The rock types that are intermediate between acidic and basic include trachites, diorites and andesites. They are easily break down into the fine textured soils due to their mineral components. So the rocks that are intermediate between acidic and basic rocks the examples include trachites, diorites and andesites they easily break down into the fine textured soils due to their mineral components. The clay portion of the fine textured soil is the result of the primary rock minerals decomposed to form secondary minerals not small fragments of the parent rock minerals. The properties and behavior of the clay soils are different from those of gravel, sand and silty soils. So the clay portion of the fine textured soil is the result of the primary rock minerals decomposing to form secondary minerals. So the properties and behavior of clay soils are different from those of gravel and sand and silty soils. This is one of the reason for different behavior of the properties of the clay. When it comes to sedimentary rocks these are actually formed from the accumulated deposits of soil particles or remains of certain organisms that become hardened by pressure or cemented by minerals. Cementing materials such as silica, calcium carbonate, iron oxides are abundant in this type of rocks. Example limestones, dolomites the present proposal new name is dolostone and sandstone are shale or conglomerate and briscia these are the examples of the sedimentary rocks. The shales are predominantly formed from the deposited clay and silt particles. The degree of the hardness of this shale depends upon the type of minerals the bonding that developed and in the presence of foreign materials. The hardness is mainly due to the external pressures and particle bonds not due to the cementing materials that is this is mainly due to the external pressure which has been subjected and the particle bonds not due to the cementing material which is actually due to any cementing materials. When exposed to an environment water or ale shales tend to expand and de-daminate this is one of the problem in some parts where the shale soils are available and then they have planar types of failures and the slopes with very small inclinations or mild inclinations can be subjected to planar failures and breakdown of the shale the fragments of various sizes and varying sizes and clay particle sizes. So if the shale actually breaks and it gets fragmented into clay particle sizes. Limestone is predominantly crystalline calcium carbonate that is calcite formed under water. So limestone dolomite is referenced as a karst or karstic terrain and here in this particular photograph a typical formation of a sink hole which is actually shown and here this is due to the canty which is formed because of the soluble nature of the ingredients present in the ground water. So these types of formations cause problem to the infrastructure particularly pipes which are actually pipes which are located on this type of structures or any structures which are actually resting on this type of formation can be subjected to distress. So weathering of limestones predominantly fine size particles will be reduced. So what we are seeing is that we have seen igneous rocks and we have seen sedimentary rocks. Let us look into the third type of the rock which is called metamorphic rock. The source of this metamorphic rocks either igneous or sedimentary rocks. The results when any type of existing rock is subjected to metamorphism the change brought about the combinations of heat pressure and plastic flow so that the original rock structure and mineral compositions are changed. So here the plastic flow means a slow viscous movement and rearrangement within the rock mass due to external forces. So limestone after subject into metamorphism converts into marble. Shell to slate and slate or phylite, granite to gnaze and sandstone to quartzite. So if metamorphism of limestone yields to marble, metamorphism of shell yields to slate or phylite, metamorphism of granite yields to gnaze and metamorphism of sandstone yields to quartzite. The gnaze is a foliated rock with distinctive bending that results from the metamorphism of granite. Distinction between gnazes and shears is not always clear upon weathering gnaze and shears decompose to form silt sand mixers with mica content. Soils from phylites are more clay and decomposition of quartzite reduces sands and gravels. So decomposition of quartzite produces sands and gravels. Decomposition of phylites produce clay material. So this is a typical example of metamorphism which is actually shown in the site. So if you look into this slide the rocks are subdivided into igneous, sedimentary and metamorphic and when they are subjected to weathering either due to physical or chemical means and they get divided into transported or sometimes when the weathering takes place when the soils deposit at their location then that is also called a residual. So when the transported soils and the soil is now broadly classified as boulders, gravel, sand, silt and clay. So this particular gravel, sand, silt and clay if you see the size of the particle keeps on decreasing as we traverse from gravel, sand, silt and clay. So rock whose chief mineral is quartz minerals with high silica content decomposes to predominantly sandy and gravelly soil with little clay. So these are acid rocks and they are light colored in nature. Six rocks decompose to the fine textured silt and clay soils. The clays are not small fragments of the original materials that exist in the parent rock. This we have discussed earlier. This results the primary rock minerals decomposing to form secondary minerals. So if you look into this the major soil types based on the practical size if you classify just now we discussed that in the type of formation we said that the gravel, sand, silt and clay they originate from the different types of rocks. The gravel and sands are considered to be coarse grained soils with large particle sizes and silt with very tiny particles of disintegrated rocks and clay particles are considered as fine grained soils because of their small particle sizes. Clay soil is plastic over certain range of water content and still silt soil possess little or no plasticity. So clay soil is plastic in nature if it can be remolded without cracking and breaking we can say that the clay soil is plastic and over range of water content. So the practicals larger than gravel are called cobbles or boulders. So soils can be grouped into two broad categories as we see based on the deposition based on the sizes we have actually divided into different types like gravel, sand, silt and clay based on the method of deposition residual which is actually called or formed when weathering of the rock and the remaining at the and weathering of the rocks takes place and their soils remain at the location of their origin itself. This is because a material which possess little mineralogical resemblance to the parent rock. Soil which actually resembles which remains there at the origin itself and it resembles the parent rock characteristics predominantly. And there is another type which is called transported. These transported soils are called those materials that have been moved from their place of origin like by agencies like gravity, water, glaciers or man either singularity or in combination. So characteristics of the residual soils depend upon the climate conditions, humidity, temperature, rainfall. Some islands actually have the residual soils where the soil gets originated and then deposited at its place of origin. So the characteristics of these residual soils are predominantly depending upon the humidity, temperature and rainfall and the natural drainage part pattern and form an extent of the vegetation cover. So these are the prime factors on which the characteristics of the residual soils are depend on the depend. Now the transported soils we said that there is an agency which actually transports if it is transported by running water then it is called alluvial deposits and if they are deposited in quite lakes they are called lochestrine deposits. If they are deposited in seawater and they are called as marine deposits, if they have been transported by wind or air then it is called aeolian deposits and if there is a glaciation which actually takes place because of the large movements of the sheets of ice then they are called glacial deposits. These are actually predominant in hilly areas. And colluvial that is deposited through action of the landslide and slope wash where this particular types of deposits are possible. So according to the transporting agency and method of deposition we subdivide this transported soils into alluvial, lochestrine, marine, aeolian, glacial where the glaciation is predominant and colluvial deposits. Because of the transported soils are layers this is basically a windblown deposit with very uniform fine silt particle and possess a slight cementation. So this is the reason why if suppose if there are some unsupported vertical cuts they stand vertical because of the cementation which is present in the particular soil which is transported by wind. So this formed in arid and semi arid regions and with yellowish light brown color. Which is a fine grained slightly cemented volcanic ash and which is deposited by wind or water. So tuft is an example of transported soil. Glacial till is a heterogeneous mixture of boulders, gravel, sand, silt and clay which is predominantly in hilly region and where the glaciation is predominant. And warwood clay which is an example of transported soil which is nothing but which is formed by alternating layers of silt and clay deposited in fresh water with glacial lakes. One band of silt and clay deposited each year. So each layer is approximately 10 mm thick or so. So this particular transported soil is called a warwood clay. Marl very fine grained soil of marine origin imperimble and which is highly compressible and greenish in color. Heat which is highly organic soil consisting almost entirely of vegetable matter in varying stages of decompositions. So it is basically a fibrous type of material and it is fibrous in nature and brown to black in color and highly compressible deposits. So these pt soil deposits are also called as marshy lands where the construction needs to be done with care. The major soil deposits based on the ambience, geography and topography they are called as expansive. These expansive soils also have high shrink and swell characteristics attributed to the mineral which is actually present in these expansive soils. The basic color is black. This is due to the presence of iron, magnesium and titanium. Marine deposit very soft and may contain organic matter and laterate soil red in color due to Fe2O3 and the loss of silica which is due to the intense chemical weathering and this particular loss of silica due to the intense chemical weathering is called laterization and this causes lot of problems in laterate soil deposits. Alluvial is alternate layers of sand, silt and clay and desert is nothing but a wind blown deposit and which is uniformly graded in nature. This is a boulder clay which consists of all ranges of particle sizes. Here the distribution of the predominant soil deposits in India are shown here in this particular slide where in this portion where the desert soils which are actually transported by wind are shown here. Basically here the Aeolin deposits are there and along the coastal belt the Indian coastal peninsula is about 6500 kilometers and majority of the Indian coastal peninsula has marine soil deposits and in this portion which is actually here shows the expansive soil deposits. So the construction in these areas which is difficult and in this particular portion here it is shown here the laterate soils. So if you look into north to south and west to east there are the different ranges of soils which makes engineering difficult and where there is a relevance of the subject as far as Indian context is concerned. So if you look the consistency of the soil mass the formation of soils from the weathering of the parent rock and wide range of the soil solids are possible. The behavior of the soil mass under stress is a function of the material properties such as size and shape of the grains. So if you wanted to see understand about the material properties and its behavior the size and shape of the grains gradation like what type of particles and how the combination is there whether it has actually has got fine grain portion or coarse grain portion and mineralogical composition type of mineral which is actually present in the particular soil arrangement of the grains and inter particle forces. So the behavior of the soil mass under stress is a function of the material properties such as size and shape of grains, gradation, mineralogical composition, arrangement of the grain inter particle forces. So material properties are now if you look into this is a function of the constituents of the soil mass. The soil is a particulate material which means that the soil mass consists of accumulation of individual particles that are bonded together by mechanical or attractive means though not strongly as by rock. In the rock there are the materials which are actually with permanent bonding the spaces between solid particles are referred here as voids or pore spaces. The spaces between solid particles are referred here as voids or pore spaces and if these voids are filled with water then it is called pore water and they exert pressure on the voids it is called as the pore water pressure. In soil in most rock the voids exist between particles and voids may be filled with a liquid usually water, gas or usually air. So in soil if the majority of the rocks also they do have voids. So voids existing between particles and voids may be filled with air then in that case it actually is divided into if it is only predominantly air then it is called as a two phase system which will be introduced in the next slide and if it is filled with water only it is again also called as a two phase system but here it is called water saturated all the voids are actually filled with water and there is also possibility that partially saturated soil where you have got air, water and solids. So actual soil bulk consists of soil particles water and air. Air is actually occupied here in the space which is actually shown here and here is actually portion which is actually shown as with water. So this type of soil deposits which are actually above the ground water table and this particular zone from here to here is called as Vados zone and here this zone is called unsaturated soil and the soil mass which is actually there below the solids which are actually filled with water is called saturated soil here and here it is called partially saturated soil. If there is no water here then there is only air and solids and if the here below water table the soil mass is actually completely filled with soil voids are completely filled with water. The water surrounding particles at points of contact with water particles and filling in the small void spaces. So the consistence of the soil mass what we are saying is that there is a solid phase liquid phase and gaseous phase and if you have solid and gaseous or predominantly air which is called as dry state when the solid and liquid which is there predominantly then there is this phase is called as saturated state. So here a typical three phase system is shown where soil solids and you have got air and then water which is filled with the remaining portions. So idealization if you idealize this three phase system then it is called gas or air, liquid and solids. The solid phase consists of primary rock forming minerals such as greater than 2 micro meters and poor reactivity prone to disintegration. So this is basically a solid phase and clay minerals the basic material that form the soil mass size less than 2 micro meters and high reactivity and the cementing material this is basically carbonates and organic matter high water absorption compressible and unstable in nature. So solid phase which is actually there in the part of a phase system which is introduced in the previous slide this can be primary rock forming minerals and clay minerals cementing material and organic matter. Second phase basically it consists of water or dissolved salts where we have pure water or polluted water and this is polluted water because of the levels of contamination which is actually introduced in the previous slides. And the dissolved salts sometimes you have got water soluble and water insoluble and water soluble salts which are predominantly chloride sulphates and bicarbonates not capable of binding solid grains. And gaseous phase predominantly consists of air and gases and if only you have got air and solids which is called as two phase system dry soil and if you have got two phase system again with water and solids it is called as a saturated soil. So we have a dry soil saturated soil and partially saturated that is referred as three phase soil system. In the three phase soil system in order to reduce relationship between volumetric ratios and weight ratios the soil which is actually here is idealized as the three phase system is idealized as air water and solids. On the left hand side the volume is given here and the right hand side weight is actually shown here. So here W suffix S is called the weight of solids and here W is the weight of water and weight of air as 0 but it actually has got volume which is called as volume of the air volume of water. Volume of water plus volume of air is called volume of voids. That means that in the three phase soil we have got volume of voids which is actually both air and water will be there. If you have got a dry soil then you have got volume of air only. If it is a saturated soil you have got volume of water only. So here this solid portion volume is referred here as volume of solids. So if you look into this W is nothing but weight of solids plus weight of water. If suppose the weight of water is 0 in case of a dry soil then you have got weight of solids only and total volume of the soil mass is nothing but the volume of the solids and volume of the water and volume of the air. So total volume is nothing but volume of solids plus volume of voids. So this is the case for the partially saturated soil. So as a part of self-evaluation in this, so in this lecture what we have tried to understand is that we have introduced ourselves to the different modules which are actually going to be there in this particular advanced geotechnical engineering course and we also have discussed about the different ranges of geotechnical structures which are actually possible. Like we have said that natural slopes or slopes, embankment dams or foundations particularly building foundations and shallow foundations or deep foundations or road embankments or some windmill foundations and offshore foundations like we have ranges of geotechnical structures. All structures which are actually they are predominantly the resting in or on the soil and the soil is actually is a major predominant material and if you see a typical foundation and the foundation should transmit the loads and the settlement should be minimum so that the safety can be ensured. So all these geotechnical structures which are actually there should be understood such a way that they should not fail and ensure performance during their lifetime of the design. So in this particular lecture what we have done is that we have actually discussed about the origin of the soil. The origin of soil is predominantly basically from the rocks, predominantly that rocks are igneous sedimentary metamorphic rocks and these rocks are basically when you are actually have different states of either metamorphism can takes place because of the either source from igneous or sedimentary rocks and we also discussed that some types of sedimentary rocks which are actually have some ingredients which are soluble with in the which are present in the ground water can actually dissolve the rock and form sink holes and which these are very popular in the United Kingdom called as crastic stones or crastic formations. So as a self evolution in this I would like you to list the soil types included in coarse grain category and fine grain category. So if you come across any soil type kindly look into the type of soil and list to the soil type whether it is a coarse grain type or fine grain type and why there is a difference in behavior of natural place and other soil types such as sands and sills. At this primitive stage if you can able to understand why there is a difference in behavior of the natural place and other soil types whether any can be if you can relate to what we discussed in this lecture and this answer you will be able to answer. And what does the term plastic means in relation to clay soils and what are laterates or laterate soils and why are such soils are considered in the category of required special consideration on construction projects. And for any soil investigation project any geotechnical engineering project or any project is engineering project you require to understand about the extent of the soil horizontally as well as vertically in such situation we do at number of selected locations boreholes. So any particular from any borehole data tested in your location or if you have come across any borehole data list the soil types and rock types. So this will allow you to converse with the subject which we are going to cover in advanced geotechnical engineering course.