Structural Considerations
Wall, base and cover slab loads for a buried structure.
A maintenance hole carries vertical load from its cover and surrounding soil, lateral load from soil and groundwater, and uplift from groundwater. It is designed as a buried structure, not simply as a shaft.
The common structural elements are the base slab, the wall or riser rings, and the cover slab or cone. Precast and cast in situ construction have different jointing and continuity assumptions.
Key design considerations
- Cover class appropriate to the surface, including a heavy-duty class under traffic.
- Wall thickness and reinforcement for the depth, soil and groundwater load.
- Base slab sizing and its role in resisting uplift.
- Cover slab or cone capacity, and load transfer into the wall.
- Precast joint detail and the assumption of continuity, or lack of it.
- Concrete grade, cover to reinforcement and durability classification for aggressive ground.
- Construction loads and backfill sequence, which can govern thin walls.
Design checks
- Cover class matches the loaded surface.
- Wall and base designed for the design groundwater level.
- Durability classification consistent with soil and groundwater testing.
Standards and authority references
- Authority standard maintenance hole drawings
- AS 3600 Concrete structures
- AS 3996 Access covers and grates
Confirm the current edition, amendment and any local supplement before applying any of the above.
Limitations and assumptions
- Structural design of maintenance holes requires project-specific loads and materials.
- Standard drawings are only valid within the conditions they were prepared for.
Related calculators
This reference is general engineering information. Confirm requirements against WSA 02, the current Australian Standards and the local water authority's supplement before use in design, and obtain project-specific advice for the conditions at hand.