AbstractThe brickearth of southern England is a spatially extensive cover of Quaternary clays, silts and fine-sands that mantle the underlying Mesozoic strata. The
provenance of the material has been subject to widespread debate with many models having been developed by previous workers.
Based on the results of both geochemical tests and geotechnical tests this
research shows the brickearth to be from a single source, and trends identified within the geochemistry strongly suggest that this source lies to the east of the current brickearth outcrops. Scanning electron microscopy identified two surface textures indicative of two different transportation modes. In quartz grains finer than 200μm surficial features consistent with aeolian suspension load were observed. However, in grains greater than 200μm the surface textures were consistent with fluvial or aeolian saltation load. All the evidence implies a single source for the brickearth and that this source lies to the east of the British Isles. Given this evidence and the surficial textures of individual grains it becomes apparent the brickearth of southern England is a reworked loess and as such the term loess should be used when describing these aeolian deposits.
It is widely known that loess deposits exhibit metastable behaviour and can
collapse upon saturation. To test the collapsibility of the brickearth a series of
oedometer tests were performed on samples from Portsmouth, Hampshire. These tests revealed a moisture content below which collapse occurs. Using the principles of unsaturated soil mechanics it was possible to develop a model to predict the behaviour of the material based on the applied load and the moisture condition of the material. Given the reworked condition of much of the brickearth it is has been considered as stable, the results of the current research show that this is not necessarily the case suggesting that a process of "loessification! ' must occur to allow an open structure to form, a prerequisite for collapse to take place. Therefore, much of the hitherto stable brickearth may indeed possess the ability to collapse given the right environmental conditions.
|Date of Award||2004|
|Sponsors||Association of British Insurers|
|Supervisor||Dave Giles (Supervisor) & Nicholas Langdon (Supervisor)|