The Filton Bank 4 Track project is a major rail project to increase the number of tracks from 2 to 4 between Dr Days and Filton Abbey Wood Station in Bristol.  The project includes the construction of 15km of track and associated signalling and infrastructure works.

As part of the Filton Bank 4 Track scheme, CAN was contracted to undertake a number of cutting and embankment works to allow an increase in the width of the track bed.

Narroways Cutting comprises a 220m long cutting up to 18.5m in height.  An existing low timber sleeper retaining wall along the toe of the cutting was removed.  The base of the cutting was then steepened to 80 degrees creating additional working width for the additional tracks.

CAN installed solid tendon soil nails complete with a weldmesh reinforced spray concrete facing.  This provided permanent support and protection from weathering of the steepened toe section.  The cutting was re-graded in “bays”, minimising the risk of localised failure.  This meant that each bay was stabilised prior to cutting the adjacent one.  Each bay was subject to daily monitoring to provide early warning of movement.

CAN installed a total of 400 Dywidag soil nails ranging from 3m to 10m length, with the facing consisting of 2 layers of Hy Ten weldmesh and 250m3 of sulphate resistant sprayed concrete from Cemex.  The works were programmed efficiently to allow for variance in expected ground conditions.  Some areas of the cutting required the bays to be cut in a different order and split into further sub-bays to maintain temporary stability.  This required a working on multiple tasks in different areas of the work-site simultaneously.

Duration:        17 weeks

Client:             VINCI Construction UK Ltd

Location:        Filton, Bristol