Project overview

TechnikGS was instructed to carry out a challenging project involving piling from raised platforms in the River Croal, located in Bolton city centre. The project required the installation of piles to support raking shores and prop up an existing adjacent building before the commencement of demolition work.

The innovative concept and detailed design for the work gained approval from the Environment Agency, ensuring compliance with regulatory requirements.

Challenges

Several unique challenges were encountered in the River Croal environment, including heavy rainfall that led to flooding of the works area. A large excavator was present throughout the project to facilitate the removal of the piling rig from the working platforms in the river channel. The river was temporarily diverted and water management was closely monitored to minimise any negative impacts on the project.

The project also faced challenges associated with various ground conditions, restricted access and low headroom in certain areas of the site. The conditions were carefully assessed and considered and working methods were adapted to overcome the difficulties posed by the project’s location.

Solutions provided

To ensure minimal disturbance to the surrounding properties, TechnikGS utilised a low-noise/vibration bottom-driven process. This approach kept the vibration levels as low as possible. Bottom-driven piling is a displacement system that generates no spoil, which eliminates the risk of any material entering the adjacent river. The permanent sacrificial steel casing also avoided any potential concrete loss.

A total of 59 bottom-driven piles were installed using a combination of 273 and 323-mm-diameter casings. The piles were installed to a set resistance, which was encountered at depths of around 8 m below the working platform. The compression loads were relatively low at 100 kN, while the horizontal shear was 50 kN, which was dealt with by appropriate pile reinforcement.