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A manhole is a shaft that functions as an access point to the underground infrastructure and is covered with a very heavy lid, sometimes weighing more than 100 kg. Occasionally a strange phenomenon occurs in which such a manhole cover is lifted above its opening and sort of dances on or above its supporting ring without any human intervention. This usually happens when it is stormy with heavy rainfall, but it is not tied to one specific location. Videos from all over the world can be found on the internet showing such ’dancing manhole covers’. Sometimes air seems to be the main driving force behind the behavior, sometimes water, and sometimes both. Although the videos are funny, the behavior can create a very dangerous situation for both traffic and pedestrians. In this report, the cause of these ’dancing manhole covers’ is studied. The ’dancing’ is simplified into two different problems: one with an overflow of air and one with an overflow of water. For both problems a simple model consisting of differential equations is proposed and the numerical results are studied. The problem with an overflow of air is driven by an influx of air into the manhole from below, resulting in an increase in pressure, which lifts up the cover, until air is allowed to escape, and the pressure decreases again. Two different approaches for the escaping discharge of air are tried. The overflow of water is driven by a constant pressure that is exerted on a water column inside the manhole. Furthermore, a solution to the dancing problem is proposed: attaching the manhole cover to the ground with a hinge. This solution is tested by using a similar model as the one used for the overflow of air.
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Tilting Manhole Cover: A Nonlinear Spring-Mass System
Abstract Manhole covers are potential “dancers”. They may leave their resting state and start “dancing”. They may hover, move up and down, tilt, rotate, bounce, make noise, flip over, or even fly up into the air. In general, their motion looks chaotic, probably due to the nonlinear dynamics governing the system. The authors have previously derived basic models of dancing manhole covers covering the translational vertical motion of free covers and the rotational motion of hinged covers. In the current contribution the basic model is extended with tilting (without hinge) and bouncing behavior. Some fundamental problems and assumptions are discussed. Preliminary numerical results are shown together with 3D visualizations. Scientific curiosity into a mysterious phenomenon has been the motivation for this study. The obtained equations governing the manhole cover’s motion may serve as boundary conditions in hydraulic-pneumatic models of sewer-manhole systems (think of geysering and ventilation).
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- Award ID(s):
- 2048607
- PAR ID:
- 10636817
- Publisher / Repository:
- American Society of Mechanical Engineers
- Date Published:
- ISBN:
- 978-0-7918-8849-0
- Format(s):
- Medium: X
- Location:
- Bellevue, Washington, USA
- Sponsoring Org:
- National Science Foundation
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