As part of Network Rail’s CP6 Works Delivery Civils Framework for the North West & Central (NW&C) Route, Taziker was awarded the sheet piling/earthworks scheme in Wigan. Taziker began work in February 2019.
The scope of works included:
- Remove all existing site vegetation, rubbish and fencing from worksite location
- Remove existing king post/masonry retaining structure
- Ground investigation/buried service surveys
- Pile platform/reaction stand design & construction
- Installation of 70 lineal meters of sheet pile wall to 15m target depth
- Protective coatings to both the sheet pile & capping beam to client’s specification
- Regrade embankment to rear of new sheet pile wall
- No fines concrete infill to the southern elevation of sheet piles
- Construct reinforced concrete pilaster at south elevation
- Install 70 lineal meters of new PCC Trief kerb
- Install 80 lineal meters green powder coated palisade fence
Network Rail had identified that the existing wall adjacent to the railway line had been compromised and works were required to improve the structure and appearance. The works consisted of removing the existing king post/timber and masonry wall and installing a new sheet pile retaining wall. Taziker were also required to install a steel palisade fence and Trief kerb.
The worksite, located in the middle of a busy industrial/residential area, was bordered by a main road on two sides with the railway line on the other. Due to the noise caused by sheet piling and the volume of plant, equipment and materials required for the project, Taziker needed to carefully consider equipment options and site logistics. Additionally, the worksite did not have the capacity for welfare facilities during the works.
Before the main work began, Taziker worked with the occupier to clear and secure the site. During this phase, Taziker conducted a buried services survey. The discovery of a manhole providing access to a main sewer which ran perpendicular to the railway and beneath the proposed sheet pile wall, also meant that the original plans would no longer be acceptable.
In the original methodology, Taziker proposed that the nearby client’s compound would be used for welfare facilities and parking. To ensure the location was suitable for use, Taziker harmonised the existing compound area to facilitate its use, which minimised the impact and provided much needed space for the main worksite.
The discovery of an uncharted sewer imposed a weight restriction on a proportion of the worksite. Working with Network Rail, the works around the sewer were quickly redesigned. Site access, transport movement and equipment locations were altered to accommodate the findings and avoid the restricted area. The previously planned one-way system was now not achievable resulting in a single access/egress for all works.
For the sheet piling work, Taziker opted to use a Giken Silent Piler™, to reduce noise during the project. This meant that piling works could be programmed during the night, allowing Taziker to significantly accelerate the programme by running the piling and earthworks in tight formation, day to night. While the sheet piling took place at night, the earthworks team could work during the day to strip and remove the spoil from the front of the sheet piled wall. Unfortunately, a consequence of the sewer’s location in relation to the works forced the works to revert to daytime working whilst the operational railway remained unaffected by implementation of All Lines Open (ALO) working.
The sheet pile wall once exposed sat 3m out of the ground with an embedment depth of 12m. As part of the redesign a number of piles were installed at a shorter depth over the sewer with the addition of 2 wailing beams installed with full height welds to provide strength for the lateral loads.
The facade of the sheet pile wall was finished with a protective coating, new steel top hat and protective Trief Kerbs for vehicle incursion.
Taziker installed the retaining wall successfully following the design change, providing a strong structure to the side of the railway line and a more attractive appearance for the area.
The team worked efficiently to ensure the new retaining wall was completed to a good timeframe. By working closely with the client and land owner, Taziker were able to overcome any problems encountered, coming up with proposed and accepted solutions at each stage. Taziker demonstrated their flexibility and professionalism, completing the job to a very high standard.
Disruption to the public, through carefully considered traffic and noise management, was kept to a minimum during the entire project. Taziker’s traffic management supply chain partners installed advance warning signs for the duration of the work and managed council notifications of any disruptive deliveries.