Fortrac® geogrids provide a new housing site.

Fortrac® geogrids provide a new housing site.

Tuttle Hill, Nuneaton | HUESKER Synthetic GmbH

A disused quarry in Tuttle Hill,  has been regenerated to provide a new housing site for Redrow Homes. The former quartzite and diorite quarry, ceased operation in the late 1990’s and covers an area of 40 acres. The quarry consists of a large ‘main void’ and smaller partially in-filled ‘shallow void’.

The solution

In order to facilitate the regeneration of the site for housing the ‘shallow void’ was in-filled in order to provide a stable development platform, whilst the ‘main void’ is to be left as an open body of water.

The reclamation works comprised the following main activities:

Excavation of loose Fill from the shallow void,

Preparation and processing of materials on site for placement and the

Construction of a 35m  high Fortrac® geogrid reinforced soil slope between the ‘shallow’ and ‘main’ voids.

The design

HUESKER had provided design assistance and advice at an early stage with regard to the design of such a high embankment and the selection of a BBA certified geogrid.

Tuttle Hill, Nuneaton | HUESKER Synthetic GmbH

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The analysis of the reinforced soil embankment had to satisfy a number of temporary and permanent conditions: during construction, during recharge of the quarry lake (causing potential inundation settlement of the engineered Fills) and an allowance for a rapid lowering of the water in the quarry lake. Also future water level rises had to be taken into consideration at design stage.

Of particular concern was the post construction movement of the embankment. The vertical settlement was satisfied during construction by adopting an end-product compaction specification, whilst the horizontal movement risk was minimized by selecting a low strain criteria using Fortrac® geogrids to maintain relative density of the overall Fill.

The design of the reinforced soil slope comprised layers of high strength polyester geogrid. A range of Fortrac® geogrids were used within the slope with ultimate tensile strengths ranging between 400kN/m and 55kN/m. Primary anchor lengths varied from 35m to 8m in length.

Additionally the risk of wave action on the slope face due to the quarry lake was taken into account by using gabion stone for the lower part of the slope.