Main contractor Edmund Nuttall Ltd, were awarded a challenging contract to construct a new bridge and associated infrastructure, to service the new national stadium. An additional challenge was to cause minimal disruption to the railway line, local businesses and residents during construction. Dawson Contract Piling were awarded seven different subcontracts to carry out a wide variety of sheet pile installation and extraction works. For some applications innovative equipment was developed and new methods of working had to be implemented with safety paramount.
The work was carried out successfully and safely, well ahead of schedule. This allowed the main contractor to complete the possession and return the line to Chiltern railways well ahead of schedule.
Much of the work was carried out at night or with weekend railway possessions. Pictured here is a 50-hour weekend possession to install nearly 400No x 9.5m long x L604 piles to form a safety barrier between the works area and the railway line. Ground conditions comprised stiff London clay with cohesions in excess of 150kN/ m2. Three ABI telescopic leader rigs were used to pre-auger and then to drive the sheets using 92.5t variable moment resonance free vibrators.
Two 80t mobile cranes and two excavators were also used to move equipment, build access ramps and provide piling platforms. Pre-augering was carried out at night and vibratory driving was carried out during the day to limit disturbance.
Summary of Soil Conditions
|Layer||Depth (m BGL)||Soil Description|
|1||0.0||1.2||Mixed soil - Soft to firm|
|2||1.2||2.2||Sandy Clay - London Clay Formation|
|3||2.2||3.2||Clay - London Clay Formation|
|4||3.2||-||Clay - London Clay Formation|
Bowmer & Kirkland Ltd appointed Fussey Piling as the sheet piling contractor to design, supply and install steel sheet piles to form a 130m long permanent retaining wall to retain heights between 3.0m and 5.0m. The sheet piling contract had a value of circa £160,000 and was completed in less than 2 weeks.
As can be seen from the photographs of the site, the ground conditions encountered were chalk. The sections used were 7.0m to 12.0m Arcelor Mittal PU sheet piles in steel grade 355GP. The piles were installed with the Bauer RTG16T telescopic leader rig, which vibrates the piles to the required level using a high frequency variable moment vibrator.
Graham Hall, Contracts & Commercial Manager, said “This is the first time we have worked with Bowmer & Kirkland on a sheet piling project. They gave us all the attendances we required which enabled us to complete the project ahead of time with the minimum of ‘fuss’. We have received a letter of recommendation from them and look forward to working with them again soon.”