This is a relatively new (in comparison to many decades old of soil mechanics theories) but very useful concept in soil mechanics. It is a topic that is analysed in advanced soil mechanics courses only, in masters level classes, but it doesn’t prevent us from at least describing it, as it is good to know […]
Natural slopes tend to slide or fall to their lower side, given long enough time. Depending on the saturation degree of soil, the slope angle, overall 3D geometry, and the soil material itself, this sliding or falling can happen in very different ways and speeds, some can be very slow and virtually harmless, and some […]
Consolidation settlement is a time dependent settlement that occurs in clay soils, due to applied loads from above. As we wrote before, settlement of soils in general has three stages: The immediate settlement as the load is applied, which is elastic settlement, the gradual, slow consolidation settlement while water is escaping through soil pores, and […]
After finding stresses in soil, we can calculate settlement amount. Settlement of soils in general has three stages: The immediate settlement as the load is applied, which is elastic settlement, (for all soils) the gradual, slow consolidation settlement while water is escaping through soil pores, (for cohesive soils only) and the secondary compression due to […]
We have looked at bearing capacity of the soil in the previous section but checking only that is not enough. We must also make sure that, even if the soil can bear the pressure, it will not settle too much. Before calculating settlement amount in soil however, we must first know the stresses in soil. […]
So far, under soil strength section, we have explained total and effective stresses, pore pressure, angle of internal friction, shear strength, lateral earth pressure coefficient, and cohesion of clay. Now we are ready to start seeing how these are actually used, when designing foundations. In this subsection we will now learn about bearing strength, […]
Cohesion, although thought to have only one meaning by many engineers, actually has two close meanings to each other. One meaning is in soil physics, which means, is the attraction of particles in soil, creating a sticking action. The other meaning comes for soil mechanics, and it means the shear strength of soil, when there […]
We talked about angle of internal friction of soil, in previous posts of this series. There is also the angle of repose, which is often confused with angle of internal friction. Angle of repose is the angle a soil forms with the horizontal, when poured over a surface in it’s loosest state. Although angle of […]
A more complicated version of direct shear test which we talked about in the previous post, is called triaxial test, where you can also control the water drainage turning off or on, plus you can measure at what angle the sample will shear, which we will talk about more in the following paragraphs. Both of […]
When we want to test the shear strength of soil vs. how much we press on it vertically, we can use a mechanism like below, which is called direct shear test. It is the most basic shear test method for soil. In it’s simplest from it can be shown as: Direct shear test is a […]