Case study: massive voids

Two and a half thousand cubic metres of voiding and redundant access tunnels underneath a mail order firm’s distribution centre in Manchester were filled without disrupting commercial operations using the Benefil bulk void filling system.

At the same time, the material stabilised floor slabs had dipped due to heavy loading.

“The floor in question acted as a link between loading docks to the building and a large automated warehouse,” says Richard Harries of Clancy Consulting Engineers. “The quantity of goods coming across this floor was so considerable that even short down-periods couldn’t be considered – the facility is used virtually 24/7.”

Replacing the floor was considered, but rejected due to the large amount of dust and debris that would be created. Excavating to introduce a new suspended floor was also looked at, but turned down on health and safety grounds allied to factors of disruption and difficulty of access. Infilling the gap between the floor and the ground was decided upon, and Benefil was chosen partly because the lightweight polymer resin would add minimal loading to the fill material, but mainly due to its lack of disruption.

Benefil’s team were able to fill most of the void filling from below using the existing tunnel system. For those areas which remained inaccessible, portable equipment was taken onto the floor of the warehouse. The Benefil polymer resin can be injected up to 100m from the supply tanks, which allowed the delivery hoses to be placed via overhead steelwork, out of the way of warehouse operations.

Individual sections of the facility, including areas underneath conveyor belts, were isolated on a day by day basis for the repair to proceed. Depending on access, the team were able to fill up to 185 cubic metres per day and stabilise the floors.

“We lost just one bay at a time, work within the warehouse carried on, health and safety issues were minimal, and it progressed in a way that has caused little or no disruption,” says Richard Harries. “The client is delighted.”