What is the "haunch zone" in an excavation?

The haunch zone in an excavation refers to the area adjacent to the bottom quarter of a pipe, primarily where the pipe's arching structure supports and distributes load effectively. This zone is critical as it ensures that soil load is properly transferred from the surrounding ground to the pipe, helping to maintain structural integrity and prevent issues such as pipe deformation or failure.

Understanding the haunch zone is essential for ensuring proper backfill and compaction techniques in trenching operations, as inadequate support in this area can lead to significant problems for buried pipes. Proper attention to the haunch zone during installation and maintenance activities can help mitigate risks associated with settlement or collapse of the trench, which can have serious repercussions for the collection system's performance.