2. Types of Piles

In today's presentation, we are going to discuss about the different types of piles. We can classify them based on application, material type, method of fabrication, and installation process. There are many ways to classify piles, and I will provide an overview of the merits and demerits of different types of piles.

In this chunk, the instructor outlines the different ways we can categorize piles. Piles are crucial structural components designed to support buildings and other structures by transferring loads to the ground. The classification involves four main aspects: application (how and where they are used), material type (the substance they are made from), method of fabrication (how they are constructed), and installation process (how they are placed in the ground). Understanding these classifications influences decision-making in construction projects.

Think of classifying piles like sorting fruits in a market. Just as we can classify fruits by type (citrus, berries, etc.), size, or ripeness, we can classify piles in similar ways. Understanding these categories helps builders choose the right pile for their specific needs, much like a shopper chooses fruits for a special recipe.

First, let us see what are these sheet piles. Sheet piles are steel sheets with interlocking joints that act as a rigid barrier for earth and water, particularly during excavations or trenching. They protect trenches from soil collapse and can be used in water as a cofferdam, providing a dry working area.

Sheet piles are often used in construction to create barriers against soil and water. Their interlocking design allows them to form a strong wall that can prevent soil from collapsing during excavations. They are particularly useful in areas where excavation sites are near water, as they can also stop water from flooding the site, creating a safe and dry environment for workers. Sheet piles can be made of various materials, including timber, steel, or concrete, depending on the project's requirements.

Imagine you're trying to dig a deep hole in sandy beach. Without any support, the sides of the hole would collapse, making it hard to keep digging. By using something like a strong wall around your hole (similar to a sheet pile), you can keep the sides stable and keep working safely—even if water is nearby.

Other types of applications are end bearing pile and the friction pile, based on the mode of load transfer. End bearing piles transfer the load through the weakest strata till they reach a hard bearing strata, while friction piles get load bearing capacity from friction between the pile sides and the surrounding soil.

This chunk discusses two primary types of deep foundation piles: end bearing and friction piles. End bearing piles are designed to transfer loads directly to a harder layer of soil or rock beneath the weaker top layers. This means their effectiveness relies on reaching a stable, load-bearing stratum. On the other hand, friction piles do not rely solely on a strong layer beneath; instead, they get their load-bearing capacity from the friction between the pile's surface and the surrounding soil, making them effective in situations where a hard stratum is too deep to reach.

Consider trying to push a stick into sand. If you can't reach the hard ground underneath, the stick will just slide down into the sand (like friction piles). However, if you push hard enough and the stick hits a rock below, it can't go down any further—that's like end bearing piles finding solid ground to support weight.

Timber piles are the oldest known material used for deep foundations. They are inexpensive and easy to use, but they can be susceptible to rotting and insect attacks, especially if subjected to fluctuating water tables. Preserving timber piles is crucial to maximize their service life.

Timber piles have been utilized for centuries due to their low cost and the ease with which they can be cut and shaped. However, timber is vulnerable to decay and pests if it is not properly treated. For instance, if timber is exposed to fluctuating water levels, it may rot since both water and air can penetrate the wood. Therefore, effective preservation methods are essential to ensure these piles last longer. Special treatments, like soaking in preservative solutions, can significantly improve their lifespan.

Think of a wooden dock by a lake. If the wood is treated and remains submerged, it can last a long time. However, if the water level fluctuates frequently, the wood is exposed to air, which can lead to rotting, just like untreated timber piles at construction sites. That's why treating the wood properly is like giving it a 'raincoat'—to keep it safe from the elements.

Concrete piles provide high load-bearing capacity and resistance to decay. They can be classified as cast in situ or precast. Cast in situ piles can be made using either the displacement method or the non-displacement method.

Concrete piles are an excellent choice for construction because they have a high load-bearing capacity and do not deteriorate like timber. There are two primary ways to create concrete piles: precast, where they are made in a factory and transported to the site, and cast in situ, where they are constructed on-site. The installation of cast in situ piles can be further categorized into displacement methods, where the soil is displaced during installation, and non-displacement methods, which minimize disturbance to the soil.

Imagine pushing a thick cake into a pile of frosting. If the cake disturbs the frosting a lot (displacement method), it will make a mess everywhere, but if you slide it carefully into the frosting (non-displacement method), it stays cleaner and preserves the frosting. Similarly, the 'cleaner' method is often better for maintaining the soil around the piles.

--