Duddeston Junction

HS2 is a project to construct a new high-speed railway line between London and Birmingham. As part of this project, an element of these works is to construct the Duddeston junction Viaduct asset.

Duddeston Junction Viaduct is a multi-span structure supported on a mixture of columns and portal frames which span transversely over the Network Rail tracks and River Rea. The extent of this asset’s spans between GL33B, 34 and 35A and with the working area situated between a number of live rail lines Created a large challenge for the client. 

This scheme required the construction of 56 number 750mm diameter rotary bored piles to depths of 22m whilst being constructed under Bentonite support fluid due to the none cohesive strata over the top element of the piles with rock formations below.

With the constraints of the site but the need to construct the piles under bentonite and be able to create rock sockets Martello Piling utilized the MP6000 series rigs to construct the 56 piles spread over GL33b, GL34 and GL35b.

One of the largest challenges was around logistics with the working site situated as an island between several of live rail lines either side. Receiving deliveries and moving equipment to and from the Island inclusive of muck away had to be well managed and planned with Network Rail to gain line blocks to pass over the two RRAP’s. Cages being the larges commodity required on the platform but with space as a premium, the task of having an ample supply but not overwhelm the capacity of the platform had to be executed to very small margins.

On top of the logistical challenge there was also the challenge of getting Bentonite and Concrete to the island and onward to the pile locations. This was overcome by a number of well planned routes running from the Bentonite farm to the island however these routes took the distance of the lines in excess of 200m. A similar situation occurred with the concrete lines however with a smaller distance to travel.

The installation of the cages posed yet another challenge as the design parameters dictated heavy reinforcement using up to 9 number B50 bars within a 600mm diameter cage. Due to the proximity to the live rail lines these cages had to be restricted in height, therefore with section length of 3.5m the only solution to attached each section fell on the use of 50mm Lenton positional couplers. With the help of Total Reinforcement we managed to overcome the constructability constraints surrounding these reinforcement cages.