1.1.2 - Self propelled or towed
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Smooth Wheeled Steel Drum Rollers
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Today, let’s delve into the smooth wheeled steel drum rollers. They range in capacity from 20 kN to 200 kN, and they can be self-propelled or towed.
What type of soils are these rollers suitable for?
They are best for well-graded sand, gravel, and silt of low plasticity. However, they are not suitable for uniform sand, silty sand, and soft clay.
Is there a mnemonic to remember this?
Yes! You can use the acronym 'GSS' for 'Gravel, Sand, Silty silt' — which helps recall suitable soils!
What is the significance of their capacity?
The capacity of these rollers affects their function. Higher capacities allow better compaction on larger projects.
In summary, smooth wheeled steel drum rollers are ideal for well-graded materials and vary significantly in weight and propulsion.
Pneumatic Tyred Rollers
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Moving on to pneumatic tyred rollers, these usually have two axles and carry rubber tyres across the full width of their track.
What unique features do they have?
They can have an added dead load of water, working effectively between 100 and 400 kN.
What soils are they effective on?
They handle most coarse and fine soils, but they struggle with very soft clay and highly variable soil.
Is there a way to remember their weight range?
You could remember 'HWT' for 'Heavy Water Tyred', as it links the concept of weight with the water used as dead load.
To summarize, pneumatic tyred rollers have unique characteristics and applications that make them versatile for most soils, with specific limitations.
Sheepsfoot Rollers
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We’ll now discuss sheepsfoot rollers. They can either be self-propelled or towed.
What’s unique about their structure?
They have drums equipped with projecting club-shaped feet designed to provide a distinct kneading action.
How much do they weigh?
Sheepsfoot rollers weigh between 50 to 80 kN, making them suitable primarily for fine-grained soils, sand, and gravel with high fines.
Can we use an acronym to remember this as well?
Absolutely! Use 'FGS' — 'Fine-grained, Gravel & Sand' to help remember their suitability.
In conclusion, sheepsfoot rollers excel in specific soil types due to their unique kneading action.
Introduction & Overview
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Quick Overview
Standard
The section discusses different types of compaction equipment, specifically focusing on their propulsion types (self-propelled vs. towed) and their suitability for various soil types. Specific machines such as smooth-wheeled, pneumatic-tyred, and sheepsfoot rollers are examined.
Detailed
Detailed Summary
Types of Field Compaction Equipment
This section identifies and elaborates on various types of field compaction equipment, primarily categorized as either self-propelled or towed machines. The main types discussed include:
- Smooth Wheeled Steel Drum Rollers:
- Capacities range from 20 kN to 200 kN.
- Can be either self-propelled or towed.
- Ideal for well-graded sand, gravel, and low plasticity silt but unsuitable for uniform sand, silty sand, and soft clay.
- Pneumatic Tyred Rollers:
- Typically have two axles fitted with rubber tyres covering the entire width of the track.
- Additional dead loads (water) can be added for a total weight range of 100 to 400 kN.
- Effective for various coarse and fine soils but not suitable for very soft clay and highly variable soil.
- Sheepsfoot Rollers:
- Can also be self-propelled or towed.
- Feature drums fitted with projecting club-shaped feet to enhance kneading action.
- Weighs between 50 to 80 kN, ideally suited for fine-grained soil, sand, and gravel with considerable fines.
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Self Propelled vs. Towed Equipment
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Chapter Content
- Self propelled or towed
Detailed Explanation
This point indicates that the smooth wheeled steel drum rollers can either move on their own (self-propelled) or can be pulled by another machine (towed). Self-propelled equipment has its own engine and is capable of moving independently without needing another vehicle. On the other hand, towed equipment relies on another vehicle, such as a tractor, to pull it across the ground. Understanding the difference is important for choosing the right equipment based on the construction site layout and the task at hand.
Examples & Analogies
Imagine a car (self-propelled) driving on its own versus a trailer (towed) being pulled by a car. The car can go anywhere without assistance, while the trailer can only move if the car is present to pull it along. Similarly, self-propelled rollers can navigate freely on a worksite, while towed rollers depend on a tractor for movement.
Specifications of Smooth Wheeled Steel Drum Rollers
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Chapter Content
- Capacity 20 kN to 200 kN
Detailed Explanation
The capacity range of smooth wheeled steel drum rollers is between 20 kN to 200 kN. This refers to the amount of force that the rollers can exert when compacting soil. 'kN' stands for kilonewtons, a unit of force. The higher the capacity, the more pressure the roller can apply, which influences its effectiveness in compacting different types of soil. A higher capacity roller may be needed for denser soils, while lower capacities suffice for softer soils.
Examples & Analogies
Think of a weightlifter who can lift small weights versus someone who can handle very heavy weights. The lighter weightlifter can be effective for certain tasks but might struggle with heavier loads. Similarly, smooth wheeled steel drum rollers have capacities suited for different soil types, and using the right one for the job ensures the best results in soil compaction.
Soil Suitability for Smooth Wheeled Steel Drum Rollers
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Chapter Content
- Suitable for well graded sand, gravel, silt of low plasticity
Detailed Explanation
Smooth wheeled steel drum rollers are best used on well-graded sand, gravel, and low-plasticity silt. 'Well-graded' means that the soil has a mix of different sizes of particles, allowing for better packing and stability. This type of soil is ideal for compaction because it can fill in gaps between larger particles, providing a denser material. Low plasticity silt also compacts well, making these rollers effective in achieving a solid base for construction.
Examples & Analogies
Imagine packing grocery bags with balls of different sizes. If you use various sized balls, they fit together better and make the bag sturdier. In the same way, well-graded soils provide a tighter, more stable compaction, leading to a strong foundation.
Soil Unsuitability for Smooth Wheeled Steel Drum Rollers
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Chapter Content
- Unsuitable for uniform sand, silty sand and soft clay
Detailed Explanation
Smooth wheeled steel drum rollers are not suitable for uniform sand, silty sand, and soft clay. Uniform sand has similar-sized particles, which makes it harder for the roller to create effective compaction as there are more voids between particles. Silty sand can also be tricky since the fine particles may not provide enough structure for effective compaction. Soft clay is too pliable, and the weight of the roller could cause it to sink into the material rather than effectively compact it.
Examples & Analogies
Consider trying to pack a suitcase with only soft clothes (like t-shirts): they can be squished, but they don’t create a sturdy structure, and items easily settle into softer parts. Similarly, using a roller on soft clay or uniform soil doesn't yield the desired compacted surface needed for construction.
Key Concepts
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Self-propelled: Machinery that can move on its own, providing more flexibility at job sites.
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Towed equipment: Machinery that requires another vehicle for movement, often used for larger machines.
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Soil Suitability: Different types of compactors are suited for different soil types, affecting the efficiency of the compaction process.
Examples & Applications
Example 1: A smooth-wheeled roller is used for compacting a gravel road base as it's well-graded and offers suitable density.
Example 2: A pneumatic-tired roller is applied on a construction site to compact clay surfaces, but might struggle if the clay is too soft or variable.
Memory Aids
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Rhymes
Smooth rollers roll with ease, in sands and gravels they're the tease, not in clays they'll bring a squeeze.
Stories
Imagine a construction site where the smooth rollers danced smoothly on the gravel, while the sheepsfoot kneaded the soft earth, creating a perfect road.
Memory Tools
For soil types: 'GSS' - Gravel, Sand, Silt (suitable for smooth rollers).
Acronyms
For pneumatic tyred rollers
'HWT' - Heavy Water Tyred.
Flash Cards
Glossary
- Compaction Equipment
Machines used in civil engineering to compact soil and other materials.
- Selfpropelled
Machinery that can move under its own power.
- Towed Equipment
Machinery that is pulled by another vehicle.
- Wellgraded Soil
Soil with a range of sizes of particles, leading to effective compaction.
- Plasticity
The measure of how easily a substance can change shape without breaking.
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