Objective The development and utilization of urban underground space constitutes a significant component of contemporary urban construction, with the three dimensional geological model serving as a foundational element in the evaluation of the complexity involved in the development and utilization of underground space. Addressing the challenge of inaccurate stratigraphic zoning in existing three−dimensional geological modelling methods, this paper proposes a rational calculation method for determining the stratigraphic pinch−out location, taking into account the factors that influence model accuracy.

Methods The method determines the pinch−out position by considering formation thickness, borehole spacing, formation burial depth, and single−hole control range. This is achieved by tracking the formation partition, thereby constructing a more accurate formation surface.

Results This study selected Beihai City as the research area. Utilizing actual geological data from the region, including boreholes and profiles, a unified stratigraphic sequence was first established, and stratigraphic zoning constraints were generated. Subsequently, a refined three-dimensional geological structure model of Beihai City was successfully constructed. The model’s quality was evaluated through borehole data back-substitution and profile comparisons, and a comparative analysis was conducted against traditional modeling methods. This comparison revealed that the model constructed using the proposed method exhibited a higher degree of conformity with actual borehole-revealed conditions in key areas, and the stratigraphic contact relationships were more reasonably represented.

Conclusions The proposed method for calculating stratigraphic pinch-out locations based on influencing factors effectively enhances the accuracy of three-dimensional geological models, particularly demonstrating a significant advantage when dealing with complex geological structures involving features such as pinch-outs and unconformable contacts. Compared to traditional modeling approaches, the model developed with this method aligns more closely with actual geological conditions. It offers a novel and more reliable solution for addressing challenges in three-dimensional geological modeling under complex geological settings, and holds important reference value for the refined development and utilization of urban underground space.