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Questions and Answers
Which engineering profession is related to roads and underground pipes?
Which engineering profession is related to roads and underground pipes?
- Geotechnical Engineer
- Housing Contractor
- Civil Engineer (correct)
- Electrical Engineer
What are the different forms of drainage?
What are the different forms of drainage?
- Natural (correct)
- Sub-surface (correct)
- Man-made (correct)
- Surface water (correct)
What factors govern the arrangement of a drainage scheme?
What factors govern the arrangement of a drainage scheme?
Internal layout, external pipe position, building connections, public pipe locations, and topography.
Which materials are classified as rigid drainpipes?
Which materials are classified as rigid drainpipes?
What does SANS 559 specify about VC pipes?
What does SANS 559 specify about VC pipes?
Vitrified clay pipes are commonly used nowadays.
Vitrified clay pipes are commonly used nowadays.
Name two features installed in manholes for access.
Name two features installed in manholes for access.
The minimum groundwater infiltration in manholes is to contribute to the _____
The minimum groundwater infiltration in manholes is to contribute to the _____
What is the maximum gradient for pipes in drainage systems?
What is the maximum gradient for pipes in drainage systems?
What is the minimum cover for drainage pipes?
What is the minimum cover for drainage pipes?
What type of joints were caulked joints replaced by?
What type of joints were caulked joints replaced by?
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Study Notes
Introduction to Drainage
- Civil engineers handle surface water via roads and underground pipes (water mains, foul sewers, stormwater).
- Housing contractors focus on internal and external plumbing for potable water and wastewater removal.
- Geotechnical engineers assess sub-surface water and its impact on soil conditions, particularly the water table.
Types of Drainage
- Various forms include:
- Surface water drainage
- Sub-surface drainage
- Natural drainage systems
- Man-made drainage systems
Drainage Scheme Arrangement
- Influenced by:
- Internal layout connections
- External pipe placements
- Relations between buildings
- Locations of public sewer and stormwater pipes
- Topographical elements
Drainage Materials
- Rigid drainpipes are made from clay (domestic use) and cast iron.
- Flexible options include pitch fibre and unplasterised PVC.
Vitrified Clay Pipes (VC Pipes)
- VC pipes are largely obsolete due to brittleness.
- Specifications governed by:
- SANS 559: Covers physical properties, dimensional tolerances, and testing.
- SANS 974: Defines rubber joint ring specifications.
- SANS 058: Installation standards for non-pressure pipelines.
- SANS 1200 series: Standardized civil engineering specifications.
Specifying Clay Pipes
- Must comply with SANS 559 regulations.
- Mechanical joints should be flexible, adhering to SANS 974 for rubber rings.
- Always consult relevant coding practices during specification.
Clay Pipes - Joint Details
- Discontinuation of caulking materials due to:
- Lack of flexibility causing rigidity and ground movement issues.
- Vulnerability of cement-based mortars to bacterial expansion and cracking.
- Requirement of skilled labor for caulking operations.
- Mechanical flexible joints now used:
- Rolling rubber ring
- Elastomer spigot and socket
- Sleeve and spigot
- Plain-ended pipes with jointing sleeves and gaskets
Drainage Requirements
- Adhere to local authority regulations for drainage system gradients, maximum of 1:6 and minimum of 1:60.
- Minimum cover for pipes is 800mm, with concrete encasement of 150mm for shallower installations.
- Accessibility for cleaning and inspections is essential.
- Flexible joints used to avoid cracking.
Manhole Specifications
- Spacing between manholes is determined by sewer size and cleaning equipment used.
- General advantages of manhole placement include:
- Changes in direction or gradient
- Junction points
- Head of each sewer
- Intervals not exceeding 100m for straight runs.
- Designed to minimize groundwater infiltration; typically made of bricks or precast concrete.
- Manhole shaft dimensions usually are 600x600mm or 750mm for precast.
Installation Considerations
- Schedule pipe laying and backfilling promptly post-excavation.
- Ensure correct earth cover during backfilling to prevent overload.
- Follow trench width specifications accurately to maintain structural integrity.
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