 Hello, I am Dr. Satish Kumar Kashi, Professor Walshan Institute of Technology, Sulapur presenting a topic Introduction to Foundations. Learning outcomes of this session, at the end of this session students will be able to define foundations, classify foundations in shallow and deep, describe various types of shallow foundations used in civil engineering constructions. What is a foundation? Foundation is the element of a structure which connects it to the ground and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics in the design of foundation elements of the structure. What are requirements of a good foundation? Basically it shall sustain as well as transmit the dead and the imposed loads to the soil. It should not cause excessive settlement leading to the instability of the structures. At the same time the differential settlements are to be avoided by the foundation by providing a rigid base and then the location of the foundation chosen must be an area that is not affected or influenced by future work or future factors, the depth of foundation. The depth of foundation depends upon the availability of adequate bearing capacity at a particular depth, then the depth of shrinkage and swelling in case of clay soils, then the depth of frost penetration in case of fine sand and silt stratum, possibility of excavations nearby in future, the depth of groundwater table, its variation over the period of time. Minimum depth of foundation in any case should not be less than 50 centimeter. Now here we are different common types of building foundation. So this is first that is a simple wall footing. This is a wall and this is a footing. This is simple spread column footing. So this is a column, this is simple spread provided in form of footing. Here there is a footing which is provided to a column with the pedestals or steps. Here this is a column which is provided with sloped footing. Here we have two columns which are provided with a combined footing. Here this is a strap footing. So here there are two columns, here there is a strap and these are the footings of individual foundations. Here we have a footing which is called as a mat or a raft foundation. So here these are the columns of a particular building and this column ultimately transfer a load to this particular raft or a mat. Here there is a pile foundation. So here this is a column and load is transferred from column to the pile caps and from pile caps to the piles. Here this is a drilled pier foundation and structure stability. Foundation provides the structure stability from the ground by distributing the weight of the structure over large area so as to avoid overloading of the soil beneath. It means we load the soil up to its safe bearing capacity and not more than that. By loading this substratum evenly and thus prevent unequal settlement one can understand that if the load is not spread evenly then there will be differential settlement in between the columns and their foundations. It is also important to provide a level surface for building operations and by taking the structure deep into ground and thus increasing its stability and preventing overloading. Now this is a very simple sketch which tells us about the major building part. So this is say a building a part of building above the ground is called as superstructure below the ground this particular part is called as substructure and below that we have the foundation. Now let us classify the foundation. The foundations can be classified basically in two parts. One is shallow foundation and another is deep foundation. What is shallow foundation? The foundations in which depth at which the foundation is laid is less than the width of foundation that is d less than b we call it as a shallow foundation. It is generally termed as spread footing as they transport the load of superstructure laterally into the ground. What about deep foundations? We call the foundation as a deep foundation when the depth of foundation is greater than the width of the foundation. Such that the d by b ratio is usually 4 to 5 for deep foundation say like a pile foundations or so. Deep foundations transmit the load of superstructure vertically to the rock strata like deep shallow foundations. Let us define shallow foundation. A shallow foundation is a type of building foundation that transfers building loads to the earth very near to surface. Shallow foundations include wall footings, isolated column or column footings, combined footings, cantilever strap footings, mat or raft foundation. See this a typical shallow foundation which is provided for a RCC frame structure and these is a frame structure. These are the columns and these columns are provided these footings. The footings are provided at shallow depths hence we call it as a shallow footing. Here these are the isolated footings provided for the columns. In this case we observe so this is a frame structure building but which is constructed on that way a weak strata. So here raft foundation is provided as you observe. Now this is a cross section of a brick wall with footing. So this is a brick wall these are the steps provided and this is constructed over this cement concrete 148 footing. When we have a load bearing say brick wall or masonry wall we provide say a strip type of foundation as shown in this particular figure. Simple sloped and step footing. So here this is a column and this is a simple footing. This can be further modified for better strength is this is a column and here it is sloped footing is provided here sloped footing is provided here. Here we have one more modification this is a column and here we have provided the steps to distribute load better and to have the footing economical. Let us see the practical examples. So isolated column footing so you can observe different isolated column footings provided at the side here. It is economical for the depth greater than 1.5 meter. The base of the column is enlarged as shown here constructed through plain or reinforced concrete. Here we observe the typical RCC column and column footing. Just have an idea of the reinforcement which is provided in the column and column footing. This is the 3D view, this is the top view, this is the sectional view. Another shallow foundation is Glage foundation. Glage foundation is often used at the base of columns carrying heavy loads. It consists of 1, 2 or 3 layers of steel eye sections and then all this particular system is ultimately encased in the concrete. Now let us go to combined footings. Combined footings are constructed for two or more columns when they are close to each other and their foundations overlap if you provide separate foundation for every column. The function of a footing or a foundation is to transmit the load from the structure to the underlying soil. The choice of suitable type of footing depends on the depth at which the bearing start allies the soil condition and the type of superstructure. Now the combined footing may be rectangular, trapezoidal or T-shaped. The geometric proportions and shape so fixed is such that the centroid of the footing area coincides with the resultant of a column load. So you can have trapezoidal or you can have rectangular footing. So here you can see a rectangular combined footing. This is the top view, this is the section, this is rectangular combined footing with slab and beam. This is a strap type. So you can observe in this figure a typical rectangular combined footing provided for two columns. We can also have sometimes combined spread and strip footing as shown in this figure. One can also have a cantilever of strap footing. It consists of two single footings, footing one, footing two connected with a beam or a strap and supported two single columns. This type replaces a combined footing and it is more economical. Just have idea of the reinforcement of CC strap footing. You can also have balanced and cantilever footings. So here this is footing one, here this is footing two but this column is facing to this footing. Why? It is applied when balanced footing is required when one of the footing has limited space for bearing, the footing one as we observe here, limited space for footing. When difference in soil bearing capacity is there or the loads in balanced footings are transferred from one footing to another by means of cantilever action through this member by cantilever action. What is the difference between combined? It has a single footing and balanced or cantilever footing has two separate footings connected by strap beam. Let us have some question answers. The type of foundation used when footing of adjustment columns are too close or overlap, raft, strap, strip, answer is combined. Rap foundations are used when total area of individual footing or a building is less than 50 percent loaded area, more than 50 percent, less than 75, more than 75, answer is more than 50. Third, the type of shallow foundation that can be used when the soil at shallow depth is very weak or highly compressible, raft, strap, strip combined answer is a raft. These are the references. Thank you.