Making sense of Chalk: a total-rock approach to its Engineering Geology

Abstract

The building of a new applied geology for the Chalk has been a two-way process between academic research and learning from industry which aspects of the geology are of special importance to construction projects and hydrogeology. The 11th Glossop Lecture explores the development of ideas that have led to the remapping of the English Chalk, recognition of an applied lithostratigraphy and fracture stratigraphy, greater understanding of material behaviour and enhanced conceptual models on which numerical models can be built. Advances in technology, particularly borehole camera logs and geophysical logs, are considered in the context of acquiring more reliable information for the description and classification of chalk. Construction projects used to assess aspects of chalk engineering include assessing rock mass descriptions and classifications for tunnelling on the A26 Cuilfail Tunnel, Lewes, and A27 Southwick Tunnels, Brighton; earthworks in relation to karst features on the A27 Brighton Bypass; risk analysis in relation to tunnel boring machine tunnelling through flints in the Shoreham Harbour Waste Water Tunnel; recognizing the impact of different Chalk formations on tunnels and shafts on the Brighton and Hove Stormwater Tunnel; dealing with unexpected geology on the A303 Stonehenge Tunnel; developing and applying techniques to borehole core-logging on the Channel Tunnel Rail Link, Crossrail and the Thames and Lee tunnels in east London. The feedback from discoveries made during construction to ‘pure’ geology is shown to be crucial to the subject’s development in the UK.