Manhole and its estimation
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What is manhole?
A manhole is an
access point to an underground utility or sewer system, typically round in
shape and ranging from 36 to 96 inches in diameter. Manholes are equipped
with a ladder or rungs to allow personnel to safely enter and exit, and are
outfitted with a lid or cover to prevent unauthorized entry and protect
individuals from falling in. Estimating a manhole involves calculating the
quantities of materials needed for construction, such as cement concrete,
reinforcement steel, and plastering.
Components of manhole
- Access Shaft
- Working Chamber
- Sidewall and Base
- Bottom or Invert
- Ladder or Steps
- Cover and Frame
The key steps in estimating manhole
- Determining the size and depth of the manhole based on the type of pipe it will connect to and the expected traffic load
- Calculating the volume of excavation required
- Estimating the quantity of bed concrete, manhole wall concrete, canopy concrete, riser concrete, and benching concrete
- Determining the amount of reinforcement steel needed
- Estimating the quantity of plastering required for the interior walls
fig: Manhole