A strategic and novel field trial to investigate the dynamic performance of cement-stabilised chalk as embankment fill for high-speed rail earthworks

Significant quantities of site won fill material are generated from the High Speed Two (HS2) C23 main works civil engineering contract, during the excavation for the formation of cuttings and construction of tunnels. This study investigates the suitability of weathered structureless Chalk, stabilised with cement, for use as engineered embankment fill for high-speed rail earthworks. Given the dynamic loading conditions imposed by high-speed high frequency rail operations, the performance of stabilised chalk requires thorough evaluation. A strategic field trial embankment was constructed to assess the suitability of this material. The results demonstrate that the static stiffness modulus (EV2) of the stabilised chalk meets HS2’s minimum performance requirements, though it is found to be sensitive to cement curing time. Dynamic performance, evaluated through shear wave velocity (Vs) derived from Rayleigh wave characteristics, exceeded the minimum Vs assumed for engineered fill during detailed design, confirming compliance with HS2’s dynamic performance criteria. Construction control measures, including optimal chalk grade, binder mix, moisture content, and compaction control are recommended to ensure consistent performance. These findings validate the use of cement-stabilised chalk fill for high-speed rail earthworks, enabling the development of sustainable earthwork solutions through material optimisation, waste reduction, and enhanced environmental efficiency.