Tilting Manhole Covers

Dancing manhole covers are mainly known from videos placed on the internet. During periods of heavy rainfall sewer systems get overloaded and all sorts of undesired events take place, of which geysering probably is the most spectacular. Interesting behavior is also seen from manhole covers lifted from their supports. Sometimes they seem to float on water or even on air. And sometimes they are blown off like a rocket. Knowing that the covers weigh from 50 to 100 kg and above, this is an amazing sight. Nevertheless, the situation is dangerous for traffic: vehicles and pedestrians. Dancing also poses issues for the operators of stormwater systems, who need to re-install the displaced covers and who may have to deal with the associated legal liability. The authors attempt to understand the “dancing behavior” from basic mechanistic and mathematical models. Previous models of manhole covers without hinge have been geometrically symmetric: the cover moves vertically up and down. Herein, the introduction of asymmetry is proposed via a non-central point of application of the upward force, caused by an assumed non-uniform pressure distribution underneath the cover. This should result in tilting due to torque, next to vertical displacement.