Manhole – Purpose, Types, Features and Construction
Manholes allow for vertical pipes to flow between main sewers and branch sewers. The inlet pipe of this type of manhole is higher than the outlet pipe when the inlet pipe is in steep terrain. Stop inverts are located at the same level as outlets invert in a manhole.
It is uneconomical to construct drop manholes due to their steep sloping gradient. To access utilities such as sewers, drainage systems, etc., manholes and inspection chambers are prevalent underground. Manholes are used to inspect, modify, clean, and maintain underground utilities.
Purpose of Manhole
Manholes can be used for joining sewers, rerouting sewers, and aligning sewers. Foul gases can escape through a perforated cover. As a result, it is an effective means of ventilation for the underground sewage system. It is necessary to inspect the sewer line, clean it, and remove obstructions. A manhole is necessary for laying sewer lines in conventional lengths.
Construction of Manhole
Excavation
Manhole construction starts here. Excavation occurs as indicated on the plan and in the drawing concerning the dimension and depth of the manhole. It is important to allow some digging width so that workers can work freely.
Concrete Bed
For manhole depths from 4.25 meters to above 4.25 meters, you should have a minimum of 20 cm to 30 cm of concrete in the bed. It is necessary to build a special foundation in areas with loose soil. In place of the concrete paste, the bed of the manhole is covered with a 1:4:8 concrete pastes.