Keller’s vibro compaction rigs are heading back to Mansfield to work on a major expansion of Sports Direct’s distribution centre.
Keller was last on site in 2007 when it carried out a successful dynamic deep compaction project on behalf of East Midlands Development Agency for warehousing which was subsequently taken by Sports Direct.
The warehousing became a major distribution facility for successful retailer Sports Direct and has been performing to expectations since 2007; now Sports Direct wants more space.
As part of its original contract Keller treated to a depth of 7m to 8m previous backfilled opencast coal workings containing a mixture of mudstone sand and clays.
The backfill was improved to a post treatment bearing pressure of some 50kN/m2 beneath the floor and 120kN/m2 beneath the foundations, all with predicted long term settlements of some 25mm.
Now consultant RPS has joined forces with Keller to work out how the remainder of the site can be further treated and a further programme of dynamic deep compaction (DDC) and bottom feed vibro treatment has been designed.
The most economical way to treat deep fills is with DDC and Keller and RPS’ objective was to try and maximize the extent of the site that can be treated with this method without affecting operation of the distribution centre by inducing annoying vibrations into the building.
Keller’s experience suggested that with high energy compaction necessary to treat deep fills a safe distance of 25m should be maintained from the warehouse and of 10m from an electricity substation and services.
Bottom feed vibro is proposed within these exclusion zones, and work starts this month.
The DDC has begun well and the early results from measuring the prints made by an 8t weight falling from 12m suggest that the treated area should perform as predicted. Zone Load Testing is proposed and this will also further confirm performance of the treated ground.