Otago Polytechnic
Luciano Crudo 1

Manual adjustment of manholes

A Civil Engineering student's work experience inspired a practical research project.

Lucianos Marco Crudo has been working for a company undertaking road resealing. His job included adjusting the height of the manhole cover so that it would be level with the final road surface. The cover sits on a pre-cast concrete riser, and the height of the riser was adjusted using wooden wedges which are then concreted into place. The work was time-consuming and involved repetitive lifting of the riser, which weighs about 30kg. There's also a risk that the lid might move a little before concreting occurs, and some of the poured concrete can fall down the manhole.

For his research project for the final year of his degree, Luciano sought a better way to carry out height adjustment for manhole covers. He designed and produced a set of steel pins with brackets to hold a cover. The pins have a thread which enables the height of the brackets to be adjusted by turning the pins. Once the concrete riser has been placed around the hole, the cover is positioned at the right height above it by winding up the pins. An adjustable steel skirt is then fitted inside the manhole temporarily while the concrete is poured and sets, to stop concrete falling into the manhole chamber below.

Luciano's trials with the prototype pins suggest that the task would be significantly faster and his method also reduces manual lifting.  Senior engineers in three different organisations are interested in his initiative. Further trials are needed now, and a cost-effective way of producing the pins in bulk.

December 2019