Driveability aspects of tubular piles in chalk

The Colne Valley Viaduct is a planned bridge, part of the High Speed line HS2 phase 1, designed to be 3.4 km long. VolkerStevin Ltd. has been commissioned by Align to install approximately 394 no. tubular piles over four different jetties (Jetty A to D) required for the construction of the HS2 Colne Valley Viaduct. Geobest B.V., as subcontractor to Volker Stevin, performed several driveability studies for this project. All steel tubular piles, of different dimensions and penetration lengths, will be installed in hard chalk layers. The main challenge has been to predict the expected pile resistance (SRD), as pile driving in chalk is subject to significant uncertainty. Literature also provides little and also varying guidance on how to estimate soil resistance to driving in chalk. In this document, the process leading to the prediction of the expected pile resistance is discussed. Driving records are then used to verify the performed prognosis and to back calculate the driving resistance in the chalk layers. In conclusion, insights are given on how to approach future chalk projects.