3.1. Soil Type and Associated Blow Energy

So, we have discussed about the functioning of different types of hammers and let us discuss about how to make the hammer selection. Your pile material type, the soil type everything is going to govern your selection of your pile hammer. So, with respect to material type as I told you particularly for the concrete piles you should be very careful, we should go for heavier hammer, heavier in the sense you can go for drop or single acting hammers which are basically heavier. So, if you go for heavier hammer, you can reduce the height of fall, that will reduce the driving stresses on the concrete pile head. So, that is why for concrete piles go for drop or single acting hammer with a fall less than 0.5 meter.

When selecting a pile hammer, the type of materials being used for the pile and the type of soil in which it will be driven are critical factors. For concrete piles specifically, it is recommended to use heavier hammer types, such as drop hammers or single acting hammers. The reason for this recommendation is that a heavier hammer can effectively drive the pile with a lower height of fall. This minimizes stress on the concrete pile head, reducing the risk of damage during installation.

Think of driving a nail into a wall. If you use a lightweight hammer, you might have to swing it harder and hit the nail multiple times to get it in. But with a heavier hammer, you can give it a solid hit once or twice, driving it deep with minimal effort. Similarly, using a heavier hammer for concrete piles helps in effectively placing them with less risk of breakage.

Now how to make the pile hammer selection with respect to your soil type, as I told you we can classify the soil into different categories. So, based upon there are some standard tests to categorize the soil into different categories. Like once this test is your standard penetration test where you find what is the number of blows needed for the standard penetration. So, based upon the number of blows you classify the soils into different categories.

The selection of the pile hammer must also consider the type of soil in which the pile will be driven. Soil can be categorized through standard tests, the most common being the Standard Penetration Test (SPT). This test measures how many blows it takes to drive a standard sampler a certain distance into the soil. Based on the number of blows recorded, soils are classified into various categories, such as cohesive and non-cohesive soils.

It's similar to testing the hardness of different types of fruit. For example, tapping a watermelon (soft) requires less force compared to a coconut (hard). Similarly, different soils require different forces to penetrate, which helps determine the right hammer needed for the job.

One basic guideline we need to keep in mind is for very tough soil conditions, it is preferable always go for heavier hammer, which is nothing but your drop hammer or single acting hammer that is always heavier, single acting hammer for tough soil condition and for the heavier pile. So, for lighter conditions, it is preferable to go for double acting hammer.

An important guideline for selecting a hammer is based on soil toughness. For very strong and tough soil conditions, using a heavier hammer is advisable. This can be a drop hammer or a single acting hammer, both of which provide the necessary force to penetrate dense materials. In contrast, for lighter soil conditions, a double acting hammer can be sufficient and is often preferred due to its efficiency.

Consider an athlete running on different terrains. Running on a sand-filled track (lighter conditions) allows for speed, while running on a hard, dry surface (tough conditions) requires more strength and effort. Just like the athlete would adapt their approach based on the terrain, the choice of hammer adapts to the toughness of the soil.

So, with this basic guideline let us discuss what are the guidelines available from U.S army corps of engineers. So, for very loose to loose sand, it is given that for concrete pile or the wood pile you can go for double acting. So, I mentioned that for concrete pile it is preferable to go for single acting hammer. But if the soil condition is very loose, in that case it is exceptional, you can also go for double acting hammer even if it is concrete pile.

Specific recommendations vary based on the type of soil encountered. For example, the U.S. Army Corps of Engineers suggests that for very loose sand, both concrete and wood piles can utilize a double acting hammer. This is an exception since, in general, single acting hammers are preferred for concrete piles. However, when the soil is very loose, a double acting hammer can be effective.

Imagine a construction scenario where different tools are available. You might prefer a drill for hard surfaces but switch to a lighter tool like a screwdriver for soft materials. Similarly, in construction, hammer selection adapts to the conditions of the soil to ensure optimal results.

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