Design of Manhole >6m depth
Design of Manhole >6m depth
(OP)
I am designing a manhole with a depth of 8m. Is there any special considerations I should be aware of?
does it have to be a huge chamber (& what is a rest chamber)?
does it have to be a huge chamber (& what is a rest chamber)?





RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
Per OSHA Standards 29 CFR 1910.27
Cages or wells (except as provided in subparagraph (5) of this paragraph) conforming to the dimensions shown in figures D-7, D-8, and D-9 shall be provided on ladders of more than 20 feet to a maximum unbroken length of 30 feet
applications.
1910.27(d)(2)
"Landing platforms." When ladders are used to ascend to heights exceeding 20 feet (except on chimneys), landing platforms shall be provided for each 30 feet of height or fraction thereof, except that, where no cage, well, or ladder safety device is provided, landing platforms shall be provided for each 20 feet of height or fraction thereof. Each ladder section shall be offset from adjacent sections. Where installation conditions (even for a short, unbroken length) require that adjacent sections be offset, landing platforms shall be provided at each offset.
..1910.27(d)(5)
1910.27(d)(5)
"Ladder safety devices." Ladder safety devices may be used on tower, water tank, and chimney ladders over 20 feet in unbroken length in lieu of cage protection. No landing platform is required in these cases. All ladder safety devices such as those that incorporate lifebelts, friction brakes, and sliding attachments shall meet the design requirements of the ladders which they serve.
http://www.osha.gov/pls/oshaweb/owadisp.show_docum...
RE: Design of Manhole >6m depth
You should take care when placing the landing slabs that the opening to the chamber below is about 90 degrees from the opening you have just climbed through. That is, looking on plan, if you go down a hole at 12 o'clock position, the opening on the landing should be around the 3 o'clock or 9'o'clock position ideally.
RE: Design of Manhole >6m depth
Such a deep manhole is quite rare and you are clearly uncomfortable with the design issues. If it was me I'd be looing for someone with the relevant experience to assist in the design. I wouldn't take the risk without it...
RE: Design of Manhole >6m depth
So, for a deep manhole you would expect operatives entering the confined space to have gas detectors, be carrying self-saver air supply kits, be fully trained and possibly wearing a body harness connected to a lanyard which is in turn connected to a winch on the surface. The winch operator is on the surface and can haul out an unconscious operative should the need arise. Your design should allow them to do this. You may need to chat to those who are using it before completing the design.
It is incumbent upon the operatives to have a safe system of work in place prior to entering the manhole.
If you don't want to consider the risks.........don't build the manhole.
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
Diplomacy Has Failed Time For Some Action
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
Two weeks to St Pats Day, mate. Slainte...
I'd be weary of infiltration via the sidewalls. I'd eiher manage the infiltration or lock it out. Alike RJLDesign's suggestions, if you lock out the infiltration, you many need to beef up the joints and may need to add ballast if friction alone can't overcome bouyancy.
I agree with DickySewerRat...don't encourage entry by specifying steps or ladders. Yes, standard specifications will indicate this-that...however, this is not a standard manhole...this is more like a mine shaft. Don't forget to specify lockable access. I'd work with a GC to look at constructibilty, constraints, etc..
Good luck,
H.
RE: Design of Manhole >6m depth
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
Entry into a manhole requires blowers for ventilation, a four gas meter,body harness and life line attached to a retrival system, training in confined space entry, a top man a competent person, a written confined space entry permit and a written confined space entry plan
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
RE: Design of Manhole >6m depth
The philosiphy is that any unauthorised person gaining access to a manhole incorporating step irons or ladders will have a readily available means of entry down to the bottom. Once there, they can become asphyxiated or swept away in the flow at their leisure. By not providing any means of entry, your average undesirable will not attempt to jump in as there is clearly no way out. those who should be entering the manhole will turn up with ladders winches, harnesses and gas detectors and enter the manhole in a safe and controlled manner.