2.4. Recommendations for Stiff Cohesive Soil

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.

When dealing with tough soils, like stiff cohesive soils, it's important to use a heavier hammer. A heavier hammer provides more force, which is necessary to drive piles effectively into these dense materials. The drop hammer and single acting hammer are recommended because they deliver a significant blow energy that helps overcome the resistance posed by tough soils.

Think of it like driving a nail into a thick piece of wood: using a heavier hammer makes it easier to drive the nail in quickly, rather than struggling with a lighter hammer that doesn't provide enough force.

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.

Cohesive soils can be divided based on their stiffness, which is measured in blows needed to penetrate the soil. For very stiff to hard cohesive soil, it is advised to always use a heavy hammer. Single acting hammers are preferred because they provide sufficient energy to drive piles into the toughest soils, ensuring that the pile installation is effective and secure.

Imagine trying to plant a tree in rocky soil. A heavier digging tool (like a large spade) is needed to break through the tough surface than a small trowel, ensuring that the roots can be planted deep enough.

For stiff cohesive soil, you can go for single acting hammer for concrete pile and double acting hammer for steel pile.

In stiff cohesive soil situations, different types of piles require specific hammer types. For concrete piles, the single acting hammer is most beneficial due to the heavier load it is designed to handle, while double acting hammers may be suitable for steel piles because they help efficiently deliver power to drive them into the ground quickly without excess strain.

Think of different tools for two jobs: a heavy sledgehammer is great for driving stakes of wood, but a precision mallet can be more effective for installing metal components, which need less force but still require accuracy.

But here they are not recommending vibratory hammer because it is stiff cohesive. Vibratory hammer can be recommended only for soft, medium cohesive soil where the blow range is 0 to 8.

Vibratory hammers are not recommended for stiff cohesive soils because these types of hammers work best in softer soil conditions. When the soil is too stiff, the vibratory action may not provide enough force to drive the piles effectively. Therefore, it's essential to assess the soil type and choose the method that will ensure the best results.

Just like you wouldn't use a soft rubber hammer to drive a stake into hard concrete, using a vibratory hammer in stiff soil is inefficient. It's better to match the right tool with the right material for the job.

Based upon the material type and based upon the soil type, so you can make the hammer selection. So, that is why I told you first we have to do some geotechnique investigations basic investigations such as site to categorize the soil type.

In conclusion, selecting the right hammer for driving piles is a complicated process that requires understanding both the type of material used for the piles and the type of soil they will be placed in. Proper geotechnical investigation to categorize soil types is a critical first step in this process to ensure effective hammer selection for various conditions.

Imagine planning a foundation for a house. Just as you would need a solid understanding of the ground conditions before choosing how deep to dig and what type of materials to use, selecting the correct hammer also requires knowledge of the soil to ensure the structure is built on a strong base.

--