HS2 Phase One

Combined Soil Stabilisation Ltd has been working on the Central 1 portion of HS2 Phase One that is being delivered by the Align joint venture for a total of 3 years this August. The initial site trials were undertaken in 2019 and following which the works commenced onsite. Over the three years CSSL has treated over 1.5million cubic metres of material for mainline embankment works, including below ground treatments. Temporary works completed include working platforms for temporary works compounds, batchers and concrete casting facilities for tunnel segments and viaduct sections. Site access and haul roads have all been constructed using stabilised materials, including spine roads for the placement of the tunnel spoil.
During the works in 2020 CSSL was the first UK company to use Continuous Compaction Control (CCC) on earthworks, working with Bomag on the development of the Bomap system and have now collected over two years’ worth of CCC data.
The Align team, along with its earthworks designers Jacobs and the temporary works designers from the McAlpine Design Group, have fully embraced the use of soil modification and stabilisation for permanent and temporary works. For the heavily loaded casting facilities, haul roads, both the tunnel and viaduct launching platforms, stabilised materials were used as a foundation with a thin imported stone covering reducing the cost of the works, providing value engineering solutions to the client. Jacobs also specified soil treatment for the below ground turnover treatment, along the mainline alignment within the head/chalk strata, negating the need for expensive imported stone, reducing the cost for the client and reducing the construction period. With restricted delivery slots on some entrances to the site, the use of soil treatment reduced the pressure on the programme, as a single load of binder could replace up to 75 loads of imported stone.
It has been a pleasure working on the project within a team that has fully embraced both the economic and programme benefits of stabilisation. With the first part of the works nearing completion, we look forward to returning in 2023 for the south embankment works and continuing the relationship with Align and its supply chain partners.