Geotechnical engineering informatization urgently needs to strengthen the integration and sharing of big data and multi-disciplinary cooperation. The successful experience of BIM technology in the field of engineering construction enlightens us to apply BIM technology to development of geotechnical engineering informatization. However

the main problem is that the data standards of geological model and BIM model are not unified. In order to solve this problem

we propose the idea of adopting BIM data standard IFC for geological models. This paper established an extended IFC-3DGeoMdl model by using entity extension and attribute set extension schema for 3D geological models. On account of the existing IFC object types

the model derived the corresponding geological-physical elements and geological-spatial structural elements

and yielded spatial expression forms of geological physical elements. In addition

with the use of the existing relationship classes in IFC

the relationships of geological physical elements and spatial structural elements were defined. Further

based on the attribute expression in IFC

the extension of attributes such as stratigraphic information and physical mechanics parameters of geological elements was realized. Finally

the paper gave a concrete implementation process of modelling

and used the actual engineering examples to verify the practical application of the extended model. The result shows that the model can effectively realize the integration of 3D geological model and BIM structural model

so as to provide effective integration and sharing of geological information for structural design and geotechnical engineering construction.