Subgrade geology beneath railways in Manchester

It is not sufficient to identify fine-grained soils, only, as locations for potential subgrade problems as could be done using a traditional 2D geological map. More information is required about the geological structure, lithological variability, mineralogy, moisture content and geotechnical properties of the soil, much of which can be supplied by modern 3D geospatial databases. These databases can be interrogated at key depths to show the wide variability of geological materials and conditions beneath the ground surface. Geological outcrop and thickness of bedrock an superficial deposits (soils), plus the permeability and water table level are predicted from the Manchester geospatial model that is based on 6500 borehole records. Geological sections along railway routes are modelled and the locations of problem soils such as alluvium, till and glaciolacustrine deposits at outcrop and shallow subcrop are identified. Spatial attribution of geotechnical data and simple methods to recast sections in engineering geological terms are demonstrated.