Abstract:

[Context] Boreholes contain abundant karst spatial information, but the data is highly discrete and difficult to describe directly the spatial morphology of karst. [Methods] In this paper, the Tongshanyuan viaduct is taken as an example. The drilling data of each stage is comprehensively collected; six indicators of karst development elevation, height, and probability are selected; and mathematical statistics and index scatter diagram are used to conduct single and multiple indicator analysis, to explore the optimal combination method of multiple indicators of karst morphology, and to obtain the statistical law and distribution characteristics of karst morphology. [Results] The study shows that: (1) a single index reflects the local characteristics of different aspects of karst morphology. (2) The multi-index scatter map drawn according to the order of karst cave floor elevation from low to high has significant regularity, which could determine the shallow karst base level. Through the relationship between the borehole karst cave floor elevation and the shallow karst base level, the borehole karst can be divided into deep karst DD class and shallow karst SD class. (3) Different types of karst in the engineering geological plan has obvious zoning characteristics, and different karst forms in the profile map has great differences in engineering geological conditions. (4) According to the classification of karst types, the survey, design, and construction are more targeted. [Conclusion] The karst multi-index scatter map method could effectively solve the difficulty of karst morphology judgment in engineering construction and could use a large number of long-term accumulated borehole data to provide a basis for quantitative analysis of regional karst development.

Key words: engineering survey, karst morphology, shallow corrosion base level, karst index, index scatter map