Manhole Covers

either damaged or not seated properly.

manhole; if it not in place it could flip, but it will never fall down in the hole, unlike a square cover. perry

BUT IT'S STILL ROUND, falling in not a problem, GA anyway

Its either the wrong manhole for the duty or the wrong vehicle for the manhole. Easy RELATIVITY

A game of tiddly-winks will illustrate quite nicely.

I read somewhere a while back how streets are prepared for Indy Car races. One of the preparations involve welding manhole covers down. Apparently, the suction created by the car as it passes over a manhole cover at speed is so great it can actually pull the cover off and flip it into the air.

Rubens Barichello crashed out of the 2010 Monaco Grand Prix after his rear suspension was broken by a manhole cover lifting as he drove over it.

I have seen some that can be bolted shut...

GA for that...

Something really thick and sticky like hot tar or Texas mud either on a tire or on the manhole cover creating temporary suction as the tire moves off the cover.

Just because something is difficult for you to lift does not mean that Mother Nature has the same problem. You might have an irregular seating surface (debris) so that the a downward force by a vehicle could be a net upward force. If the manhole cover has a surface area greater than 100 square inches, then a 100 lb manhole cover can be lifted by a pressure differential of 1 PSI. If the underground transformers get corroded by the salt from winter de-icing a brief puff of gasses at many PSI can easily lift a manhole cover. (Heck, in NYC, manhole covers have been known to destroy vehicles parked above them in Spring.)

I've heard the clinging noise of covers that are not even touched by a passing car tires; it is the vacuum wich pulls them; if the dowel pin is on, and facing the up-comming traffic, they should be ok.

But if you want a sure bet, try one of these:

a.- Totally worn out.

b.- The stretch model.

c.- Haute couture.

If they ever get flipped, flapped or pulled down, they will be instantly put back in place by the owner.

Yahlasit

The only way a man hole cover would be lifted up by a car passing over it would be by either a Formula 1 car or an Indy car passing over it. If neither of these occurred, it would have to be a blast from under the man hole cove indicating either an explosion from an equipment failure in the man hole, or an earthquake upstage passage through said channels or very nearby volcano.

Of course you could have someone passing over a manhole with a Veyron 16.4 at 228 MPH. Now that would definitely flip any man hole cover within 10 miles. Winning, just winning.

Oh that is getting old to even see in txt form...

In our road, a few manhole covers popped following excesssive rains last year. Due to incorrect channel design, the previous year, the new storm water drains were undersized. I saw this 'popping' a few times when the man-hole cover was elevated by water gushing out. Once, a car was stuck in front of the driveway because a manhole cover popped just underneath the car. Not sure if the council has done anything to rectify this. But the problem did not re-occur the last rainy season Nov - Feb.

I had no idea that water pressure could raise a solid, cast iron drain cover. [Please comment on this]. Over here we often have these stolen to be sold as scrap metal. But this time 'round blame must go to faulty design.

If the edges of the cover are conical in the correct angle (less than the friction angle) it shouldn't flip...

Broken rim of manhole under one edge.

There are several potential reasons:

1. The manhole base is out of round and does not seat the manhole cover properly.

2. The manhole base has slumped and is not perpendicular to the roadway.

3.- The manhole is worn or was not seating correctly in the base

4. The roadway has been built up over the years and when the car tire falls on the man hole it puts undue pressure on on side.

5.- The manhole is not the original one and is not seating properly

I think you better watch out for the PCG (Politically Correct Group). If I am not mistaken I believe the term "manhole" is now referred to as an "inspection chamber" (or something like that).

Obvisouly I am referring to the inspection chambers that are often found on roadways but perhaps you are referring to a differnt type of manhole

The PC term is "Maintenance Hole".

With this term, the existing road plans (where the designation 'MH' indicates a maintenance hole location) did not need to be modified.

In the early seventies, I raised the issue of a manhole cover possibly being blown out of it's collar. At the time, it seemed logical to suggest to attach them to the rest of the manhole with some kind of a hinge, so that the cover would just flip over, but not (go anywhere else) so that street crew workers could (relatively) easily flip it back into place, and go back to other work. I was promptly ridiculed for even allowing for the possibility that one could come out of it's collar because, in some cases, they weighed over 300 pounds. Silly me...

But periodically, there appeared the occasional report of a manhole cover being suddenly blown several feet in the air due to some kind of gas accummulation being ignited by an electrical spark. These were not necessarily occurring in electrical related manholes in all cases, but they happened just the same...

I've gotten a lot older, and (hopefully) a little wiser since then, so I now ask why a manhole manufacturer couldn't design them with numerous, say, half-inch diameter, holes through them to relieve at least some of the water pressure from underneath them after excessive rainfalls, and to more effectively resist the vacuum created by drivers driving badly...

Foregoing that approach, a metal ring, of rectangular cross-section, could be welded to the underside of the manhole cover to give it a thicker edge, and an appropriately larger ring could be welded directly on top of the collar, thereby raising the collar height to a correspondindingly elevated level in conjunction with a simultaneously occurring asphalt re-surfacing project, which would, in turn, make the manhole cover more difficult to remove, but still possible...

" thereby raising the collar height to a correspondindingly elevated level"

This is what is done with covers that are in household gardens. The cover can be filled with the same surfacing used in the garden so that it blends in.

As a matter of interest: why do you ask?

Because it happened---now I think I know why-- the level of the road changed with years of resurfacing and the lid was not seated properly as a result.

--

Ahhhh... The real issue is revealed...

Loose manhole covers, improper collar-seating/anchoring, semi-effective road resurfacing efforts, shoddy road maintenance efforts, etc., are more like symptoms rather than "root" problem(s)...

In the absense of further relevant information, it would appear that at least a high-quality road re-surfacing effort is now called-for, if not a total roadway reconstruction project, including a thorough evaluation of typical drainage conditions in conjunction with the costs, and kinds, of peak impacts...

Otherwise, a lesser effort would be just a new "bandaid" being put on top of the previous "bandaids"...

thank you...