Back to search result

HS2 Main Works

HS2 West Ruislip Portal Temporary Propping

The West Ruislip Portal is approximately 330m long, formed using embedded contiguous piled retaining walls. The eastern extent of the portal contains the launch chamber for the tunnel boring machines which shall dig eastward towards Old Oak Common, to form the HS2 tunnels into London Euston.  The launch chamber is 33m long, 31.5m wide and 15m deep. Due to the depth, the piles require temporary propping at capping beam level until the base slab is constructed.

The challenge

We were commissioned to design temporary propping, to facilitate the construction of the launch chamber. The propping requirements were provided by the permanent works designer, which had some extremely challenging stiffness/load design requirements.

The solution

We challenged the project designer on these requirements, and we were able to rationalise the design by halving the number of props required. 

The outcome

Through reducing the number of props required by 50% and using reusable props, we were able to reduce the carbon footprint of the project, construction risk and achieve the construction programme.

Our designers challenged the initial design requirements allowed for the development of economic design parameters (without compromising safety) and led to a reduction in the number of props.