4. Installation Methods for Concrete Piles

Next is we are going to discuss the cast in place concrete piles using displacement method. So, first is we are going to drive the steel casing into the ground, steel casing is nothing but the steel pipe, it can be either open at the bottom or it can be closed at the bottom. So, drive the steel casing into the ground this is your casing, you can see that.

This chunk introduces the concept of cast in situ concrete piles and how they are installed using a displacement method. A steel casing is driven into the ground, which serves as a pipe that houses concrete. It can either be open or closed at the bottom, influencing the type of soil displacement that occurs during the installation process.

Think of the steel casing like a straw being pushed into thick pudding. Just as the straw needs to push through the pudding to draw up a drink, the casing must be driven into the soil to create space for the concrete.

Now how do you drive it with the help of a hammer, you blow the hammer. Since there are chances are the casing may get damaged, and you have to reuse the casing for the further piling. So that is why commonly you can see that inside the casing they put this mandrel this is the mandrel. So, then you can blow the hammer on the top of the mantel to avoid the damage to the casing.

In this chunk, we learn about the driving process of the steel casing into the ground. A hammer is used to strike the top of the casing to drive it downward. To prevent damage to the casing, a mandrel, or inner rod, is placed inside it. This mandrel absorbs the impact of the hammer, protecting the casing for potential reuse in future installations.

Imagine you are using a funnel to pour sand into a bottle. If you push the funnel down too hard, it might bend or break. To protect it, you gently place a stick inside the funnel so when you push it down, the stick takes the pressure instead of the funnel.

Once it is driven to the required depth, you remove the mandrel, now place your reinforcement followed by the tremie pipe concreting. So, mostly for the pile foundation as it is for the greater depth we prefer tremie pipe method, so you do the tremie pipe concreting. After that you can remove the casing if needed or in some cases they leave the casing permanent, so that it can act like an additional reinforcement to a pile.

After driving the casing into the ground to the required depth, the mandrel is removed. Reinforcement, usually in the form of steel bars, is then placed inside the hole, followed by concrete being poured using a tremie pipe. This method is particularly useful for deep installations as it minimizes the risk of soil displacement during pouring. In some situations, the casing is left in place permanently, adding strength to the pile.

Think of building a cake in a deep, narrow cake pan. First, you put the metal support structure in (like the mandrel), then you add layers of cake mix (rebar), and finally pour icing (concrete) into the pan. If you want your cake to be stronger and not fall apart, you might leave the metal support in place.

So, if you leave the casing it is called as cased pile or if you remove the casing it is called as uncased pile. So, basically when the casing is closed with bottom, so it means that you are going to leave it permanent. So, the casing which is open at the bottom, we remove it and reuse it. So, this is a displacement method, because this driving mechanism will displace the surrounding soil.

This chunk explains the difference between cased and uncased piles based on whether the casing is removed after pouring concrete. A cased pile remains in place, providing additional support, while an uncased pile allows for the casing to be reused. Also, it reiterates that this process signifies a displacement method as the pit created for the pile disrupts the soil around it.

Think of a balloon being blown up (cased pile) versus one that you deflate after using it to shape something (uncased pile). The balloon holds its shape and supports (like the casing), but if you deflate it, you can use it again later for another purpose.

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