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A short class with Sarah and her students. The other ways are under More.
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Today we are going to learn about how to choose the right hammer for piling. Can anyone tell me why the choice of hammer is important?
I think it depends on the type of pile used.
Exactly! The material type of your pile greatly influences the hammer you should select. For example, concrete piles need a heavier hammer to prevent damage.
What kind of hammer should we use for concrete piles?
For concrete piles, we typically use drop or single acting hammers. They are heavier and help to reduce stresses on the pile head.
Soil can be categorized into cohesive and non-cohesive types. Do you remember how we classify the soil based on penetration tests?
Yes! Based on the number of blows needed for penetration.
Right! Non-cohesive soils are categorized from very loose to dense sands based on the number of blows. The tougher the condition, the heavier the hammer needed.
What about cohesive soils?
Cohesive soils are also rated based on blow counts. For very stiff soils, we always choose heavy single acting hammers for every type of pile.
Now let's discuss the performance of diesel hammers in cohesive soil. Why do you think diesel hammers are effective?
Probably because they give strong energy for driving?
Exactly! Diesel hammers perform very well when the soil conditions are tough due to their ability to deliver substantial energy to the pile.
Can they be used in all soil conditions?
They are not ideal for all conditions. For example, in loose or water-saturated soils, vibratory hammers are better suited.
Let's talk about hammer sizes. Hammer size is defined by blow energy. Can someone explain how we calculate that?
Is it the weight of the hammer times the height it falls?
Exactly! The formula is W x H. As the pile length or weight increases, so does the blow energy requirement. Hence, we need larger hammers for tougher conditions.
Does that mean lighter conditions allow smaller hammers?
Yes, for lighter conditions, you can use lighter, double acting hammers.
To summarize, hammer selection is based on pile materials and soil types. Can anyone list the types of hammers we discussed today?
Drop hammers, single acting hammers, and double acting hammers.
Plus diesel hammers for tough cohesive soils!
Great! And remember, always check soil conditions before selecting your hammer to ensure effective driving.
What if we have noise restrictions?
In that case, you should consider vibratory methods or quieter hammers!
The choice of hammer depends on pile material and soil conditions.
Soil types differ in terms of how they respond to hammering.
Determined by the weight of the hammer and the height from which it falls.
For tougher soil conditions, heavier hammers are necessary.
For heavy piles where soil's tough, a single hammer is the right stuff.
Imagine a construction site where workers are trying to drive piles into tough clay soil. They learn that using a heavy hammer helps them drive the piles deeper without cracking them, ensuring their structure stays strong.
C-H-A-M-P for remembering hammer types: Concrete = Heavy, Hammers for All types of Piles.
H.E.A.V.Y. - Hammer for Effective And Valuable Yields.
Term
What are single acting hammers?
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Term
What is blow energy?
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A hammer that delivers a blow to the pile in one direction, typically using gravity or steam pressure.
A hammer that can deliver blows in both directions, allowing for a shorter stroke and more compact design.
Soil that has the ability to stick together due to water content, often referred to in categories of stiffness based on penetration test results.
A simple hammer that is dropped from a height to drive a pile into the ground.
A type of hammer that uses vibration to reduce friction and allows faster pile driving in certain soil types.
The energy delivered to a pile during the impact of the hammer, calculated as weight times height of fall.
This section discusses the selection and performance of various pile hammers, particularly focusing on diesel hammers in cohesive soil conditions.
The section highlights the importance of hammer selection based on pile material type and soil conditions, detailing guidelines for different hammer types and their effectiveness in various types of soil, especially in cohesive soils. It emphasizes the need for heavier hammers in tough soil conditions, particularly the performance of diesel hammers.
In this section, we explore the performance of various types of pile hammers and the criteria for their selection based on both pile material type and soil conditions. Notably, diesel hammers excel in cohesive soil conditions due to their high driving resistance.
Soils are categorized based on standard penetration tests, classifying them primarily into cohesive and non-cohesive types.
The size of the hammer correlates with required blow energy, which is determined by the formula: W x H (Weight x Height of Fall). In tougher soil conditions or longer pile lengths, the blow energy requirement increases, necessitating the selection of a suitably sized hammer. It's crucial to avoid using double acting hammers for concrete piles due to their rapid blow rate which could damage the pile.
Diesel hammers deliver effective performance in cohesive soil by providing substantial energy to overcome high driving resistance. A comprehensive geotechnical investigation helps in hammer selection based on material type, soil conditions, pile length, and anticipated noise restrictions.