Case Study - Eaves Green

The client, Lancashire County Council, had designed an urban relief road in Chorley, Lancashire. The width of the scheme corridor was minimal which resulted in embankment batters that were steeper than normal. The site won general fill was a Class 1 (granular) material and there were reservations over the ability of this material to remain stable in the outer faces of the embankments.

Discussion between L.C.C.; Birse Civils, the Main contractor; and CS identified the possibility of producing a Cement Bound material for the Class 1 fill thus increasing it's stability.

Normally a CBM is used in the pavement foundation layers where it can remain un-trafficked for seven days whilst it cures and gains strength. There is no time available for this when building an embankment but equally there was, in this case, no requirement for the ultimate strengths available form cemented material. Accordingly, after the final compaction of each layer, the material for the next layer was back-tipped and spread using a LGP blade, the dump-tucks only running on the 'new' layer. This method of working thus reduced the stresses in the layer beneath.

The surface layer was constructed in the usual manner, sprayed with bitumen emulsion curing agent and left to cure for 7 seven days.