(i) The groove in a manhole serves a dual purpose: facilitating maintenance and redirecting water flow. During maintenance, shutoff boards are inserted into the groove, effectively halting upstream water flow and preventing backwater from entering. Additionally, the groove allows for water diversion, streamlining routine maintenance operations.
(ii) R.S.J.s (rolled steel joists), essentially smaller versions of universal beams, are strategically placed within manholes to withstand the concentrated stresses caused by heavy traffic loads on the narrow, upper sections. This reinforces the structure and prevents potential damage due to concentrated loading.
(iii) Double seal terminal manhole covers are employed to create an airtight seal, preventing the escape of noxious gases from the sewer or drainage system. This is crucial for maintaining air quality and safeguarding public health in surrounding areas.
(iv) U-traps with rodding arms also contribute to odor control. The U-shaped water column acts as a barrier, trapping sewer gases and preventing their release into the atmosphere. Rodding arms, usually sealed with rubber rings during normal operation, are opened during maintenance to allow for cleaning and inspection of the sewer line.
In summary, these design elements work in tandem to ensure the safe, efficient, and environmentally responsible operation of manhole and sewer/drainage systems. Each component plays a specific role, from structural reinforcement to odor control and ease of maintenance, contributing to the overall functionality and longevity of the infrastructure.