Construction and performance of chalk earthworks for High Speed One

High Speed One (HS1/CTRL) was probably the largest chalk engineering project in the UK so far this century. It was fully opened in 2007. About 40 km of its length was built through chalk geology. There was much innovation in regard to chalk earthworks for the project and the body of experience gained there informed the chalk earthworks text in the CIRIA C574 Book “Engineering in Chalk” published in 2002. With the recent start of the detailed design of High Speed Two which passes through the chalk in a similar way to HS1, it is timely to draw together, review and summarise this body of knowledge into a series of three complementary papers. This is the third in this series. It first describes the chalk compaction trials and the methodologies adopted for handling and compacting low and very low density chalk into the HS1 railway embankments, including lime treatment. The paper then discusses the approaches that were adopted for dealing with solution features in the cutting side slopes, compares UK & French chalk earthworks practice, and sustainable use of chalk excavated from tunnels along the route. Lastly the performance of the HS1 chalk earthworks over the last decade is reviewed.