Piling and Drift Filled Hollows in London

Drift Filled Hollows (DFHs) also known as ‘scour hollows’ and ‘pingo scars’ are well known tunnelling hazards in London. This paper outlines the latest research on; the geological settings, their location bias, the variation of the characteristics of known DFHs and how the features might form. The paper then sets out risks individual DFHs can present to pile type selection, piling operations and pile design.