Objectives  The cutting section analysis of three-dimensional (3D) geological model and excavation simulation of underground engineering are important functions of 3D geological modeling and visualization analysis software. The traditional explicit cutting method relies on the pre-establishment of a 3D geological body model, and the topological problem of the model is likely to lead to the phenomenon of section cavity or triangle intersection. The cutting accuracy and maximum cutting depth are limited by the modeling accuracy and depth of the existing geological body models. This paper introduces implicit functions to express multiple types of cutting planes.

  Methods  With a reasonable sequence setting of cutting operations, and based on the explicit calculation and attribute definition methods of the cutting section grids of the moving tetrahedron, a method that does not require any pre-establishment of a complete 3D geological body model is proposed. A new implicit cutting method for quickly generating geological section from geological survey source data or geotechnical survey borehole data.

  Results  A cutting analysis test is carried out for 1∶50 000 regional geological survey data and geotechnical survey borehole data. The results show that the proposed method can effectively avoid the instability problems of the cutting method caused by incorrect topology of geological body model.

  Conclusions  The proposed method supports more types of cutting planes and surfaces, controllable cutting depth and precision of cutting plane expression, which provides a new idea and reference for the spatial analysis method of 3D geological model.