Questions and Answers
What is the maximum distance for freehaul before material is considered overhaul?
How is overhaul distance measured?
Which layer is typically the strongest in layer works construction?
What is the purpose of using sub-base materials in layer works?
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Which material is classified as selected sub-grade in layer works?
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What is a crucial factor in determining the design requirements for layer works?
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What is likely to occur if the layers in layer works do not increase in strength towards the top?
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Which calculation is essential for determining the quantity of materials needed for freehaul?
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What is the primary purpose of checking the layer for compliance after construction is complete?
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Which type of material is often harvested from borrow pits?
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Which machine is most effective for medium-haul distances in soft soils?
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What measurement is crucial when determining the volume of materials transported after excavation?
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Why is it important to remove the overburden at borrow pits?
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What factor must be considered when calculating haul distances for front-end loaders?
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What is the primary consideration for economic hauling of materials?
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In what context is the transport volume measured as loose volume?
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What is the purpose of ensuring the correct volume of material is placed before compaction?
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How is the correct amount of water determined for mixing with the material?
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What role does the motor grader play in the construction process of layerworks?
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What is indicated by the need for additional water to be sprayed onto the layer during compaction?
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In what instances might surplus material from cuts be utilized?
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What is the primary reason for the construction methods employing mechanized processes?
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What type of materials are recommended for the base layer in a road construction project?
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What is the main focus of TRH 14 guidelines in road construction?
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Study Notes
Freehaul and Overhaul
- Freehaul distance defined as 500m; material carted beyond this is termed overhaul.
- Overhaul distance measured to the nearest 0.001 km.
- Mass haul diagrams should indicate all freehaul sections and quantities at each section.
- Total volume of material carted from cut to fill within freehaul range must be determined.
- Quantities of overhaul need to be calculated at each section and totaled (m3.km).
Layer Works Definition
- Layerworks consist of layers above the formation level, including:
- Selected sub-grade: one or two layers, 100-150 mm thick.
- Sub-base: one or two layers, 100-150 mm thick.
- Base layer: usually one layer, 100-150 mm thick.
Design Requirements
- Layer works must conform to design requirements based on expected vehicular traffic and loading capacity.
- Strength of layers increases towards the top to accommodate greater wheel loads.
- Proper load distribution: the base spreads loads to the sub-base, which further distributes loads to the sub-grade.
Material Types for Layer Works
- Selected sub-grade: Fair quality natural soils and sands with low plasticity; suitable surplus soil may be used.
- Sub-base: Good quality natural or processed gravels, potentially stabilized with lime or cement.
- Base: Suitably graded crushed rock or high-quality natural gravels for low-trafficked roads.
Construction Methods
- Mechanized construction entails placing the correct volume of material on approved layers.
- Water is applied according to dry density/optimum moisture content, mixed using a motor grader.
- Shaping and spreading occurs before compaction using suitable rollers.
- Layer compliance checked by contractor's foreman and client's representative for production control.
Cuttings and Borrow Pits
- Construction materials sourced from cuttings or borrow pits, requiring ground clearing and topsoil stockpiling.
- Unsuitable overburden removed from borrow pits prior to gravel extraction.
- Dense gravels ripped by bulldozer for easier loading into trucks with front-end loaders.
Transportation Efficiency
- Transportation of materials should be optimized; machinery efficiency varies with haul distances:
- Wheel-loaders effective for short hauls (up to 50m).
- Bulldozers ideal for short-distance earthmoving (30m - 200m).
- Scrapers suitable for medium hauls in soft soils and flat terrains (up to 1 km).
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Description
This quiz evaluates your understanding of freehaul and overhaul distances in construction projects. You will analyze a mass haul diagram, determine freehaul sections, calculate the total volume of material within the freehaul range, and assess the quantities of overhaul where applicable. Test your skills in earthwork calculation and improve your project management knowledge.
