Abstract: The geometric shapes of geological objects and underground openings are very complex, so it is very difficult to visualize them. This paper describes an approach for 3-D visualization of stratified geological objects and underground openings. First, the regular grid datasets of the interfaces of stratified geological objects are formed through DEM techniques; then based on the theory of medial axis transform, the shape characteristic of strata and the topologies of strata are explicitly described with thicknesses and medial surfaces of strata and a method, by which the properties of strata in arbitrary spatial position can be obtained, is established. Based on the above notion and the application of interpolation, the extraction technique of contour lines and the sweeping technique, the implementation of 3-D visualization of strata and underground openings is achieved. This method avoids complicated estimation of the properties and shapes of opening voxels and the process of computing intersection of opening faces and voxels. As an example, 3-D visualization of strata and the foundation pit of a hydropower station are carried into effect.

Key words: thicknesses of strata, medial surfaces of strata, underground openings, 3-D visualization