2.5 - Guidelines for Soft and Medium Cohesive Soil
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Pile Material Selection
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Today, we’re going to talk about how to choose the right type of hammer for different pile materials. Can anyone tell me why a heavier hammer is recommended for concrete piles?
Maybe it's to reduce the height of fall and driving stresses?
Exactly! A heavier hammer helps minimize those stresses. Now, what about timber piles?
Do we still use a drop hammer for timber as well?
Correct! Drop or single acting hammers are good for timber piles too. Now, can anyone explain what types of hammers are used for steel piles?
I think we can use double acting hammers for faster blows?
That's right! Double acting hammers are suitable for steel piles due to their rapid blow rate. Let's remember: 'Concrete = Heavy Hammer, Timber = Drop or Single Acting, Steel = Double Acting'.
Can you remind us again about the productivity impact?
Good question! For productivity, single acting hammers can be preferred over drop hammers due to their efficiency in some conditions.
In summary, selecting the right hammer depends on pile type: Concrete uses heavier hammers to reduce fall height, timber prefers lighter hammers, and steel utilizes double acting for increased speed.
Soil Classification
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Now, let’s delve into soil types and how they influence our hammer choice. What do we know about cohesive and non-cohesive soils?
Cohesive soils tend to stick together, while non-cohesive soils like sand don't.
Exactly! And how does this affect the blow energy needed for pile driving?
More blows mean tougher soil will require heavier hammers, right?
Right again! For loose sand, we might opt for double acting hammers, but for very stiff cohesive soil, heavier, single acting hammers are preferable. Why do you think that is?
Because they can provide the necessary energy to overcome the resistance?
Exactly! Remember: 'Heavier Hammer = Tougher Soil'. It's essential to assess soil type accurately before hammer selection.
In summary, cohesive vs. non-cohesive soils affects hammer choice: loose sand might allow for double acting hammers, while stiff cohesive soils will need the heavy hitters.
U.S. Army Corps of Engineers Guidelines
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Next, let’s introduce the guidelines from the U.S. Army Corps of Engineers regarding hammer selection. What’s the guideline for very loose soil conditions?
For loose sand, both concrete and wood piles can use double acting hammers, but generally single acting is preferred?
Exactly! Even though single acting hammers are generally recommended for concrete piles, exceptions are made in very loose conditions. What should we use for steel piles in similar conditions?
It’s common to use double acting as well, right?
Correct! The guidelines provide flexibility based on the soil's state. For medium non-cohesive sand, what about the suggesting hammer type for concrete and steel piles?
Single acting for concrete and either double acting or vibratory for steel?
Well done! These guidelines help ensure we select the right tools for the job considering existing soil and material conditions.
To wrap up, remember the U.S. guidelines emphasize concrete requires single acting in most cases, while loose soils permit using double acting for flexibility.
Hammer Size and Blow Energy
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Finally, let’s talk about hammer size and the relationship between its weight and blow energy. How do we calculate blow energy?
Is it the weight of the hammer times the height of the fall?
Correct! Blow energy is given by W multiplied by H. What do you think happens to blow energy requirements as pile length increases?
It increases, I assume? Heavier, longer piles would need more energy.
Exactly! The relationship is linear. For very tough soil conditions, you will need higher blow energy. Remember: 'Longer and Heavier = More Energy!' Can anyone remind us again how weight affects our selection?
Concrete piles need higher blow energy compared to timber or steel piles, right?
Right! In summary, understanding the correlation between hammer weight and required energy is vital for effective hammer selection. A heavier hammer reduces fall height and driving stresses, especially in challenging conditions.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
The section details the criteria for selecting pile hammers, emphasizing the importance of pile material (e.g., concrete, timber, steel) and soil type (cohesive vs. non-cohesive). It outlines suitable hammer types depending on the conditions, gives specific weight and energy recommendations, and references guidelines from the U.S. Army Corps of Engineers.
Detailed
In this section, we explore the relationship between pile hammer selection and both the material type of the pile and the nature of the soil. The type of hammer needed varies with the materials used for piles, such as concrete requiring heavier hammers (either drop or single acting) to minimize driving stresses, whereas steel piles might use double acting hammers for their rapid blow rate. Furthermore, soil categorization plays a significant role in hammer selection criteria, with specific guidelines provided for cohesive and non-cohesive soils. The U.S. Army Corps of Engineers offers recommendations based on soil conditions, including the use of vibratory hammers in softer soils. Additionally, the section outlines how hammer size relates to blow energy requirements, emphasizing that heavier piles and tougher soil conditions necessitate higher energy inputs to efficiently drive piles into the ground. Thus, understanding the interplay between pile type, soil characteristics, and hammer selection is crucial for successful pile driving.
Audio Book
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Introduction to Hammer Selection
Chapter 1 of 5
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Chapter Content
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.
Detailed Explanation
In this section, we explore how to select the right hammer based on two main factors: the type of pile material and the soil type. Selecting the appropriate hammer is crucial for ensuring effective pile driving, which is foundational in constructing structures safely and robustly.
Examples & Analogies
Imagine you are choosing the right tool for a job. Just like a carpenter selects between a hammer and a nail gun based on the material they are working with, an engineer must choose the right pile hammer based on the material and soil conditions they face.
Hammer Choices for Different Soil Types
Chapter 2 of 5
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Chapter Content
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, with this basic guideline let us discuss what are the guidelines available from U.S army corps of engineers.
Detailed Explanation
Understanding the soil type is vital because it affects the hammer selection process. Soil can be classified into various categories, such as cohesive and non-cohesive types. Guidelines from the U.S. Army Corps of Engineers provide recommendations on whether to use drop, single acting, double acting, or vibratory hammers based on the soil category.
Examples & Analogies
It's similar to wearing different shoes depending on the terrain. If you're walking on a soft sandy beach, flip-flops are sufficient, but for rocky trails, sturdy hiking boots are necessary. Likewise, the selected pile hammer needs to be appropriate for the soil conditions.
Guidelines for Different Soil Conditions
Chapter 3 of 5
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Chapter Content
For very loose to loose sand, it is given that for concrete piles or the wood pile you can go for double acting. ... When the number of blows are more than 50 plus, you can go for single acting hammer for steel pile.
Detailed Explanation
The guidelines detail specific hammer choices for various soil types. For instance, in very loose sand, using double acting hammers for concrete or wood piles is acceptable. As the soil becomes compacted (more blows required), single acting hammers are recommended. This reflects the need for increased energy delivery as soil resistance increases.
Examples & Analogies
Think of pushing a heavy object. If it’s on a smooth surface, a light push might suffice. But if it’s on a rough surface, you need to exert much more force. This analogy applies to hammers and soil resistance; as the soil becomes denser or tougher, more force (or energy) is required from the hammer.
Recommendations for Cohesive Soil
Chapter 4 of 5
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Chapter Content
Now we discussed about the non-cohesive sand let us now discuss about the cohesive soil. ... Vibratory hammer can be recommended only for soft, medium, cohesive soil where the blow range is 0 to 8.
Detailed Explanation
Cohesive soils are categorized based on their stiffness. For very stiff to hard cohesive soil, heavy hammers are always recommended. In cases of softer cohesive soil (where blow counts are below 8), vibratory hammers can be effective. These specific recommendations help to maximize pile installation efficiency based on soil condition.
Examples & Analogies
Imagine trying to bury a pole in sand versus clay. It's straightforward in sand (like using a light hammer), but clay requires much more effort (heavy hammer) to penetrate due to its cohesive nature. This is similar to how we select hammers based on soil types.
Final Considerations for Hammer Selection
Chapter 5 of 5
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Chapter Content
So, based upon the material type and based upon the soil type, so you can make the hammer selection.
Detailed Explanation
The final point emphasizes integrating all knowledge of material types and soil classifications to make an informed decision on hammer selection. Understanding the interplay between these components is crucial for effective pile driving.
Examples & Analogies
Selecting the right hammer is like assembling a recipe. You need to gather the right ingredients (pile and soil type) and the right cooking method (hammer type) to create a successful dish (successful pile drive). Missing one ingredient can spoil the end result.
Key Concepts
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Hammer Types: Different pile materials require specific hammer types, such as heavier for concrete and lighter for steel.
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Soil Classification: Soils are classified into cohesive and non-cohesive, which influences hammer choice.
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U.S. Guidelines: Provide structured recommendations for hammer use based on soil conditions.
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Blow Energy: Directly related to the weight and fall height of the hammer, impacting driving effectiveness.
Examples & Applications
Concrete piles generally require heavier hammers to minimize stress.
Double acting hammers are suitable for steel pile driving due to their rapid blow rate.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
For concrete so tough, a heavy hammer is key; to reduce stress and strains, just let it be!
Stories
In a world where piles were driven into the ground, a heavy hammer and a gentle hand were the heroes that reduced stress and saved the day.
Memory Tools
Remember C = Concrete (Heavy), T = Timber (Drop), S = Steel (Double). C=T, T=S, S=Double!
Acronyms
For remembering hammer types, CATS
Concrete = Heavy
Timber = Single/Drop
Steel = Double!
Flash Cards
Glossary
- Cohesive Soil
Soil that sticks together and has a high plasticity, typically clay.
- NonCohesive Soil
Soil that does not stick together easily, such as sand and gravel.
- Hammer Selection
The process of choosing the appropriate hammer type based on material and soil conditions.
- Single Acting Hammer
A hammer that delivers one blow in a single stroke, often heavier for effective driving in concrete.
- Double Acting Hammer
A hammer that delivers blows in both up and down strokes, allowing greater speed.
- Blow Energy
The energy delivered by the hammer, calculated as weight times height of fall.
Reference links
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