Creating 3D Geological Subsurface Models for Urban Areas

The successful execution of large and complex underground construction projects in urban areas increasingly depends upon a precise definition of subsurface conditions. Geological conditions dominate the cost and feasibility of these projects. Over the past two decades, a series of sophisticated 3D modeling technologies have been developed, but their routine application to shallow subsurface geotechnical site investigations has been limited. In 2001 four major constraints were identified: 1) a lack of 3D/4D mathematical, cognitive and statistical spatial tools, 2) a lack of cost-effective modeling tools designed for the shallow subsurface that can be operated without specialist personnel, 3) the inability of models to easily and accurately depict the natural variability of geological systems, and 4) a shortage of documented successful case histories. Within the past decade, these constraints have been largely overcome with the use of new modeling software and techniques and, equally importantly, with an understanding of the needs of the client. Specifically, the British Geological Survey has applied new software called GSI3D to produce high-resolution 3D models of the shallow subsurface in several urban areas. This paper demonstrates this approach with examples from the Mersey Development Corridor between Manchester and Liverpool, north-west England.