United Utilities Group PLC is the UK’s largest listed water company and was founded in 1995 as a result of a merger between North West Water and NORWEB. The group manages the regulated water and waste water network in North West England, which includes Cumbria, Cheshire, Greater Manchester, Lancashire and Merseyside – some 7 million people. The group is committed to renewing and upgrading its present water infrastructure, which often requires quite major works, including the installation of cofferdams, such as the one described here and installed by Ward & Burke Construction Limited, on its behalf.
Ward & Burke Construction Limited, have been building a series of cofferdams required to accept a tunnel boring machine and pipe jacking equipment. When building the final cofferdam they were unable to drive the sheet piles to depth due to running sand and silt. The running sand and silt was severely impacting on the company’s ability to progress and complete the installation. This turned a simple dig out of a cofferdam into a time delaying, complex geotechnical problem.
Ward & Burke Construction did initially try CFA piling, which is a potential solution for running sand problems but in this instance the depth the running sand extended from 8m down to 14m and kept biting on the auger preventing extraction of the auger and installation of the pile.
Geobear was in many ways a ‘last case scenario” for Ward & Burke. With the CFA piling option ruled out by the running sand, there were very few options left available to them. In addition, the cofferdam was being constructed within close proximity to private properties and other underground utilities, which apart from limiting options further meant any solution proposed had to be non-damaging, environmentally sound and with the absolute minimum of risk to the surrounding infrastructure.
The Geobear solution was not only suitable, but almost perfect for situations such as this. It is fast to install and without posing any risk to surrounding properties or other subsurface utilities, as well as being an extremely economical proposition.
The Geobear solution ticked all the boxes. Its specialist geopolymer resin was simply pumped into the running sand, which expanded at such a rate it became an almost integral part of the running sand. When it had solidified, it stabilised the sand more than sufficiently to provide a solid footing on which Ward & Burke could continue to work and complete the cofferdam.
Works took just over a week to complete and were undertaken on-time and to-budget with Geobear offering a non-disruptive, fast and extremely cost-effective solution. This project really was a case of “Geobear to the Rescue”, with other options completely unfeasible and the project was a real showcase of how its geopolymer solutions should be the option of choice for all deep excavation work where running sand, silt or other ground stabilisation is required.
Speaking for Ward & Burke, Niall Flood – Site agent, said: Geobear used their specialist injection technique to make a very difficult geotechnical task manageable. Their involvement was invaluable to us and was a perfect example of two specialist companies coming together, working in harmony to achieve a fantastic result. Ward & Burke will be working with Geobear again on deep excavations and we would recommend others to look at the Geobear solution.