3D Geological Model could completely and unambiguously express the spatial distribution, spatial relationship and attribute feature of the geological body, which has already been applied to the fields of energy resources, mine, urban underground space and tunnel engrineering, etc. This paper researches to build 3D geological model based on boreholes data. The process includs two kernel steps about the geological modeling: the one is constructing the topology relationship between boreholes based on Delaunay triangulation, and the other is the logical reasoning of strata linking between boreholes. Then, the 3D geological model could be built. Based on boundary representation (B-rep), the shield tunnels are built. Implementing the boolean operations between geological model and tunnels model, the underground engineering can be clearly expressed.