2.3. Guidelines for Cohesive Soil

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.

This chunk introduces the key idea that selecting the appropriate hammer for piling work depends on two main factors: the type of material used for the pile and the type of soil where the pile will be driven. The pile material can include concrete, steel, or timber, and this will dictate what kind of hammer is most effective. Similarly, the soil type significantly influences the hammer choice because different soils react differently to hammer blows, necessitating different hammer characteristics to achieve optimal results.

Think of it like choosing the right tool for a specific job. Just as you wouldn't use a screwdriver to hammer in nails, in piling work, you need to choose a hammer type that matches both your pile material and the soil conditions for the best performance.

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.

This chunk focuses on the specific recommendation for choosing hammers based on pile material, particularly concrete. It suggests opting for heavier hammers, like drop or single-acting hammers, because their increased weight can help in achieving the necessary driving force with a lower impact height. This consideration is crucial for minimizing stress on the concrete pile head during installation, reducing the risk of damage to the pile.

Imagine trying to drive a nail into a piece of wood. If you use a lightweight hammer, it may take many hits to drive the nail in without damaging the wood. Conversely, using a heavier hammer lets you drive the nail in with fewer hits and without causing splintering.

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.

This section explains the importance of classifying soil types to determine the appropriate hammer selection. It highlights that soil is usually divided into cohesive and non-cohesive categories through standard penetration tests that measure how many blows are needed to penetrate the soil. Understanding the soil's properties helps engineers choose the right hammer that will work effectively under those conditions.

It's like preparing to cook a meal; if you know you’re making a spicy dish, you’d probably choose different ingredients and cooking methods compared to a mild dish. Similarly, the type of soil dictates the appropriate hammer and technique needed for effective piling.

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.

In this chunk, specific guidelines for different soil conditions are presented, particularly from the U.S. Army Corps of Engineers. It clarifies that for very loose to loose sands, a double-acting hammer can be used for wood or concrete piles. However, the preference for a concrete pile is often a single-acting hammer due to better performance under certain conditions, emphasizing the nuanced approach required when working with various materials and soil types.

Think of it like choosing shoes for different terrains. If you're walking on soft sand, you might prefer a certain type of shoe to provide support. In piling, the recommendation for hammer types serves a similar purpose, providing the right kind of 'support' for the specific soil condition.

Now let us discuss about the cohesive soil. Cohesive soil is also classified into three different categories now let us start from the bottom. 15 to 30 plus blows indicates very stiff to hard cohesive soil, very tough soil condition in this case as I told you it is preferable to go for heavy hammer, go for single acting hammer always for all type of piles.

This section delves into how cohesive soils are categorized based on resistance to penetration, measured by the number of blows. For cohesive soils that require measuring between 15 to 30 blows, it's recommended to use a heavy, single-acting hammer since the soil is very tough and demands more driving energy during the installation of piles. The emphasis here is on understanding how soil stiffness impacts hammer selection.

Imagine trying to dig into a firm clay soil with a small shovel versus a large digging tool; the stronger your tool, the easier the job becomes. Just like the right size of hammer is needed to effectively drive piles into tough cohesive soils.

Vibratory hammer can be recommended only for soft, medium, cohesive soil where the blow range is 0 to 8. So, you can see vibratory hammer or double acting is recommended for sheet pile, double or single acting hammer you can recommend for concrete.

This final chunk discusses the best situations to use vibratory hammers. These are often used in softer, medium cohesive soils since they can effectively drive piles without exerting excessive force, reducing the risk of damaging the surrounding material. Unlike other hammers, vibratory hammers are more suited for conditions where less invasive driving is beneficial.

Think of how a massage device works. It uses vibrations to relieve tension without applying hard pressure. Similarly, vibratory hammers use less forceful driving, making them ideal for sensitive soil conditions where excessive pressure could lead to problems.

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