Riser Section Mean?
Riser sections are the hollow circular or square shaped precast concrete sections of a manhole structure that extend from the precast base to the manhole chimney. Risers can be visualized as straight sections of concrete pipe with groove joints at either end to receive the base at the bottom and the chimney at the top.
Manhole risers are also known as manhole barrel sections.
Trenchlesspedia Explains Riser Section
Riser sections are used to obtain the required height of the manhole structure. Several riser sections may be stacked vertically to increase the height of the manhole structure to the desired height.
Once the desired height of the riser section(s) is/are determined, the chimney section consisting of a conical precast concrete section and grade adjustment rings are used to obtain the final elevation of the manhole lid.
The wall thickness of the riser section must be able to resist a number of forces including hydrostatic pressure, soil active pressures, surcharge loading, and impact forces from vehicles.