Question
What are the major functions of following features observed in a typical manhole?
Answer
(i) Groove near benching, (ii) R.S.J. (iii) double seal manhole cover and (iv) u-trap with rodding arm.
(i) The groove is used to make possible maintenance of manholes and sewer or drain pipes. Shutoff boards are straight on grooves throughout preservation operation so water flow coming from upstream is terminated in manhole and backwater from downstream is also blocked. In adding, groove also facilitates water flow diversion for routine preservation operation.
(ii) R.S.J. is a small-scale size of worldwide beams and is used for resist high stresses incurred by deep traffic loads performing directly on upper narrow projected section of manholes.
(iii) Double seal terminal manhole coat are used for sealing off gases emitted inside sewer or drains and prevent them from free out of manhole.
(iv) U-trap with rodding arms is used for sealing off unpleasant gas smell by trapped u-shaped water columns. Rodding arm is usually closed with rubber rings during regular operation. Though, during protection operation, rubber ring is separate and rodding can be carried out during rodding arm