The 3D geology of London and the Thames Gateway : a modern approach to geological surveying and its relevance in the urban environment

摘要

As a provider of geological advice to industry, academia and the public, the British Geological Survey (BGS) has recognised the need to change the way it presents geoscientific information, resulting in the construction of attributed 3D geological models. The need to deliver 3D modelling solutions is of great importance in urban areas, where geological factors play a major role in supporting ground investigations and sustainable water management studies. The 3D geological model of London and the Thames Gateway occupies an area of approximately 3200 km2 and extends to a depth of 150 m. It includes a total of 38 units, ranging from Artificial Deposits and Quaternary sediments down to Tertiary and Cretaceous bedrock. The model is built using existing geological surveys, DEMs and extensive borehole and site investigation data. Modelling was carried out using GSI3D (Geological Surveying and Investigation in 3 Dimensions) software. This software and its associated workflow produce a series of gridded volumes of the geological units, constrained at depth by a network of cross-sections constructed by the geologist. The Thames Gateway model was attributed by assigning property values to each geological unit. This has provided a way of visualising the spatial relationships between geological units with differing properties. The model has revealed previously unrecognised geological information. Further benefits of the attributed model include the ability to visualise and appreciate the link between lithology and physical characteristics. Such models will produce the decision support system necessary for the sustainable development and management of today’s megacities.