Abstract: In complex geological environments, the use of simplified geometric bodies instead of real hidden karst caves for numerical analysis often fails to reflect real engineering characteristics. The naturally formed karst cave morphology lacks obvious geometric regularity, posing challenges in quantifying the characteristics of karst cave morphology. To address the lack of systematic research in the quantitative study of geometric features of hidden karst caves, this paper proposes a characterization and analysis method for hidden karst caves in borehole surrounding rock based on directional acoustic scanning. Initially, the paper utilizes borehole directional acoustic scanning technology to obtain basic data, and constructs the contour coordinate criteria for different hidden karst caves in the same borehole. Subsequently, the paper proposes horizontal and vertical structural characterization methods of hidden karst caves for quantitative characterization of the surrounding rock. The proposed methods achieve comprehensive quantitative characterization of hidden karst caves. For statistical analysis of hidden karst caves in the borehole surrounding rock, the paper introduces the horizontal omnidirectional proportion index, far-away proportion index, and depth proportion index, which can statistically analyze the distribution of hidden karst caves at different depths and surrounding locations from the borehole perspective. Finally, combined with practical engineering cases, a comprehensive analysis is carried out, which compared and validated with other methods. It can prove that the method described in this paper can provide more quantitative data for engineering investigation and numerical simulation in geological engineering in karst areas. It presents a new quantitative analysis method in the development and resource utilization technology of karst cave areas, with broad application prospects.

Key words: acoustic scanning, hidden karst caves, surrounding rock structure, quantitative characterization, karst cave analysis