hello students today we are going to learn about chapter 5 that is effective stress principle coming to the first content of this chapter it deals with the definition of geostatic stresses vertical stress or total stress [Music] what do you mean by geostatic stress stresses due to self-weight of soil are mainly known as geostatic stresses so there will be many problems in foundation engineer engineering which require a study of transmission and distribution of the stresses in large and extensive mass of soil some of the examples are wheel loads transmitted through embankments or to culverts so the foundation pressures transmitted to soil strata below the footings pressures from isolated footings transmitted to the retaining walls and wheel loads transmitted through stabilized soil pavements to the subgraded below so in such cases the stresses which are transmitted in all downward and lateral directions so estimation of vertical stresses at any point in a soil mass due to the external loading is very essential to the prediction of the settlement of the building bridges and bank environments so how the settlement of the building is taking place that one we have to uh read about it it's very important so at a point within a soil mass stresses will be developed as a result of soil lying above the point which point that is geostatic stress point and by any structural or other loading imposed onto that soil mass what do you mean by vertical order total stress when a load which is applied to soil it is carried by the soil grains and the water which are there in the pores so the total vertical stresses which are acting at a point below the ground surface is due to the weight of everything that lies above that lies above including the soil water and the surface loading so the total stress does increase with the depth and with the unit weight also so the total stress is given by sigma nothing but total load per unit area total stress is due to the self weight of the soil and overburden on the soil so this is a ground surface if you consider a one block stresses are in this direction vertical total stress as the depth is considered as z so sigma v is equal to gamma into z that is a vertical stress okay so below a water body the total stress is nothing but if there is a water body there is nothing but the some of the weight of the soil up to the surface and the weight of the water above this so soil plus water so vertical stress is equal to gamma z that is nothing but due to this gamma z plus gamma w into z w the total stress may also be denoted by sigma z or just sigma only it varies with the changes in the water level and also with the excavations so whatever stretch due to cell flow weight the vertical stress on element a if we consider a element a here can also be determined simply from the mass of the overlying material this is the mass of the overlying material so if gamma represents the unit weight of the soil so the vertical stress is given by sigma z is equal to gamma into what is the vertical distance z this is the variation of the stress with the depth it increases from top to bottom what about the stresses in a layer deposit nothing but the sum of the all individual layers like the stress in a deposit consisting of layers of soil having different densities may also be determined as sigma z is equal to gamma 1 h 1 plus gamma 2 h 2 so on till gamma and h 1 it can also be written summation i is equal to 1 to n gamma i into h i so if you take this example the vertical stress at the depth z 1 this is a depth z 1 is nothing but gamma z1 is equal to sigma z1 is equal to gamma 1 into h1 at z2 depth it is equal to gamma 1 so at the z2 it is equal to gamma 1 h1 plus gamma 2 z2 at stress at the depth z3 it is equal to gamma 1 h1 plus gamma 2 h2 plus gamma 3 h3 so the variation is accordingly drawn here thank you you