In the context of sewer pipes in architecture, haunches refer to the area of bedding material that supports the sides of the pipe, extending from the bottom up to about halfway up the pipe’s exterior. Proper haunching is crucial as it helps to transfer loads from above the pipe into the surrounding soil, preventing deformation or collapse.
Encasing involves surrounding the pipe with concrete or other supportive materials to provide additional strength and protection. This is often done in areas where the pipe might be exposed to heavy loads, unstable soil, or other conditions that could compromise its integrity.
Together, haunching and encasing ensure the stability, durability, and long-term performance of the sewer system.
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Haunches and Encasing detail drawing – 1
Haunches and Encasing for sewer pipes in construction:
Pipe Placement and Bedding:
- The sewer pipe is laid on a prepared bed of compacted material, typically sand, gravel, or crushed stone.
- The bedding thickness is usually around 100 mm (4 inches) or as specified in the design.
Haunching:
- Haunching material, typically compacted sand, gravel, or concrete, is added on both sides of the pipe, starting from the bottom and extending up to about half the diameter of the pipe.
- The haunching supports the sides of the pipe, preventing lateral movement and helping to distribute loads from above.
- Compaction is carefully done in layers to avoid damaging the pipe while ensuring stability.
Encasing (if required):
- In cases of high external loads, unstable soil, or shallow cover, the pipe may be encased in concrete for added protection.
- Concrete is poured around the pipe, fully covering it from the bedding to a height of about 150 mm (6 inches) above the pipe’s crown (top).
- The concrete may extend to the trench walls for complete structural support, creating a solid encasement.
Backfilling:
- After haunching and/or encasing, the trench is backfilled with selected material in layers, compacting each layer to avoid settlement.
- The first layers, called initial backfill, cover the pipe and provide additional protection, while the final backfill fills the remaining trench to ground level.
This combination of haunching and encasing ensures that the pipe is well-supported and protected from soil pressure, surface loads, and potential ground shifts
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