Abstract：Geological borehole is the main information for engineers to know the distribution of soil strata. In this paper，geological boreholes are abstracted as scattered point data. Each point is the demarcation point between two different strata and a topologic dimidiate data structure is designed for it. Then，the 2D section model of strata was brought out. The model represents the distribution of soil in different depths and each stratum is reconstructed by a series of triangles. In order to represent the horizontal variation of a strata，the 2.5D multi-TIN(triangulated irregular network) model is brought out. The interface between two different soils is also represented by a series of triangles in the 2.5D model. The 2D and 2.5D models were constructed by Delaunay triangulation based on the scattered point data abstracted from boreholes. Then the paper explained the modeling details and method of dealing broken mutation such as fault，dwindles and lens. At last，some assumed classical strata are constructed with the proposed method. The model is convenient for storing，analyzing，visualization and realization by computer. The conventional strata model obtained by corresponding reconstruction algorithms is almost not the final model for visualization. This modeling method based on triangulation can construct the visualization model of strata simultaneously when the reconstructed strata model is accomplished. So it unified the entity strata model and visualization model，which simplifies algorithms and data structure.
