News

September 2006

Ritchies ramps up work in the north

Geotechnical contractor Ritchies is increasingly undertaking specialist piling works, with particular activities including rock-socketed piles and marine piling

Revetments are structures placed on banks or bluffs to absorb the energy of incoming waves. They are usually built to preserve existing uses of shorelines and protect slopes. Scarborough's new revetment has been secured in place by 650 precast concrete piles installed along a 1.6 km section of the structure's toe line by Ritchies.

The original plan was to drill the 864 mm diameter holes for the 775 mm piles using a Numa 240 down-the-hole hammer from a land based rig where possible and a jack-up barge over water. The design involved socketing the piles up to 7 m into the underlying rock, but once on site it was found that the ground conditions were highly variable with an unpredictable mix of clays, sands, gravels and peat as well as rock.

Scarborough Borough Council commissioned Ritchies to undertake some further ground investigation in order to improve the piling technique and create a realistic programme. Ritchies solution was to use an auger for the land-based piles and combine the hammer with the Numa Super Jaws system to simultaneously drill and case holes for the over water piles drilled in the variable ground conditions.

The land work was completed in the first summer season and the site team continued to work from the jack-up barge, the Zeebouwer, during two further summer seasons.

DOLPHINGSTONE

Railtrack commissioned Ritchies to undertake a ground investigation in an area of old mine workings to 30 m depth under the main East Coast Main Line on the Edinburgh side of Preston Pans station in Lothian. Early results indicated the presence of workings at very shallow depths. As a result a temporary speed restriction was imposed and a Nuttall/ Ritchies joint venture, with Donaldson Associates as the designer, was asked to immediately undertake remedial work comprising further ground investigation, mine treatment, piling, deck slab construction and, finally, diversion of the track.

The piles were drilled by Ritchies using Symmetrix, leaving in the casing and a single GEWI bar was installed as additional reinforcement; 1792 no. piles with a total of 33,620 m drilling at a pile casing diameter of 244 mm were installed to depths between 6 and 35 m.

FINNIESTON BRIDGE

Ritchies completed the land-based small diameter piles for the prestige Finnieston Bridge over the River Clyde in Glasgow. The new bridge has one bus lane and one vehicle lane in each direction.

The works comprised the design and installation of 27 no. piles of 900 kN and 20 kN m capacity at the south abutment and 24 no. piles of 900 kN and 50 kNm capacity at the north abutment.

In addition, a test pile and a set of four test anchors were completed for pile testing.

TITWOOD ROAD, GLASGOW

As part of a bridge replacement on the Glasgow to East Kilbride railway line, Ritchies was appointed to undertake the installation of 26 no. temporary ground anchors and 183 no. drilled cast in-situ mini-piles drilled for the abutment and wing wall foundations.

Pile depths varied between 6-9 m. Piles closest to the track were vertical, while the others alternated between vertical and raked at 72°. To ensure failsafe working was maintained, the drill masts on the rigs were tied back. Drilling was carried out using Atlas Copco A66 and Casagrande C6 drill rigs with 6 in Cop 64 hammers and Superjaws T195 drill bits giving a 247 mm diameter hole. This allowed the same bit to be used to install casing and then drill the rock socket without having to pull the drill string.

Article courtesy of GeoDrilling International (September 2006)

Further Info

For further information, please contact:

David Gibson
Business Development Manager
Ritchies, Nailsea Wall, Kenn Pier
Clevedon, Somerset. BS21 6UE
Tel: 01275 875338
Fax:01275 870076
E-Mail: david.gibson@edmund-nuttall.co.uk

Peter Bishop
Public Relations Manager
St James House, Knoll Road, Camberley,
Surrey GU15 3XW
Tel: 01276 63484
Fax:01276 66060
E-Mail: peter.bishop@edmund-nuttall.co.uk