SUBSURFACE CHARACTERIZATION WITH SOLID MODELS

Three-dimensional computer models of construction sites and subsurface stratigraphy are useful for visualization, analysis, and design in ge otechnical engineering. A useful technique for creating such models is the geometric technique known as ''solid modeling.'' Solid modeling w as originally developed in the fields of mechanical and aerospace engi neering. In these fields, the shape and complexity of objects is relat ively simple and well defined as compared to those of the earth's surf ace and subsurface. Accordingly, because of the complex nature of the surfaces involved, most available modeling systems are not well suited for modeling earth masses. To overcome this difficulty, a technique e mploying surfaces in the form of triangulated irregular networks (TINs ) and set operations was developed. This technique facilitates the con struction of complex three-dimensional models of earth masses from dat a that are typically available to geotechnical engineers. These data u sually consist of surface-topographic surveys and borehole logs. Using the technique, a geotechnical engineer can create a three-dimensional model of a complex site. Complicated excavations can be modeled and c ross sections, or ''fence'' diagrams, can be constructed quickly and e asily, anywhere on the model, to display the soil stratigraphy at the site. Volumes of excavations and fills also can be computed easily.