 So, in this set of videos we're going to be talking about consolidation. Now, consolidation happens when we subject a soil to a change in stress. Now, we know that the solid phase within a soil is relatively incompressible, or we assume that it's incompressible, so any change in shape or volume of the soil happens because of changes within the void space. Now, water is a material that's also relatively incompressible, so if the voids are going to change shape and they're fully saturated, what needs to happen is that water needs to move out of the soil, a part of that water needs to move out of the soil, and that's what consolidation is. It's the movement of water out of the void space, so we move from a situation here to one over here where the amount of water in the soil has decreased, and what we're measuring is the settlement, so delta range. So what does settlement depend on? What does delta range depend on? Well, as we've already said, it depends on a change in stress within the soil. Well, it depends on how susceptible the material is to settlements, in some ways how squishy the material is. So a more squashy material will have a greater settlement. So we give that a parameter called the coefficient of volume compressibility, or MV, and it also depends on the total initial thickness of the material. So you take a one meter soil and you subject it to a change in stress and it has a certain susceptibility to compressibility. That will have a smaller total settlement than if you did the same for 3 meters of soil. So this settlement is proportional to the thickness of the material. So that's H0, so the initial thickness of the material. So here we have quite a simple equation for settlement, where your total settlement depends on the change in stress, your coefficient of volume compressibility, or how squishy the material is, and your initial thickness of the material. A useful thing to point out now is, or a question to answer now is, what units does this MV value have, the coefficient of volume compressibility? Well your delta range has units of length, so let's just write that in terms of meters for now. So you have a meter, a length unit here, you have a change in stress which has stress units, so let's say a kilo Newton's per meter squared. You have an unknown here, your MV value, and then you're multiplying it by another unit of length meter. Now we can see we've got it one meter up here, and we've got two meters down here, so this meter cancels with one of these, and if we then take this unit of stress, or what was a unit of stress, to the other side of the equation, if we multiply both sides by meters, and divide both sides by kilo Newton's, what we're left with is meters squared over kilo Newton's, which equals MV. So the units of MV are really just the inverse of stress units, meter squared per kilo Newton, and often those are written for convenience as meter squared per mega Newton. Okay, so let's run through an example, or a typical example of calculating total settlement within a soil.