Relationship between hydraulic conductivity of karst collapse column and its surrounding lithology

Groundwater inrush from karst collapse column (KCC) is a serious water hazard in North China. The factors determining the hydraulic conductivity of KCC remain unclear. This study analyzes the hydraulic conductivity of two KCCs from the same coal mine region and one KCC from different strata and statistically compares lithology-related data for KCCs from 11 coal mines in North China. Finally, we calculated the probability of the hydraulic conductivity of KCC and compared these calculations with field data. The results indicate that the hydraulic conductivity of KCC is mostly affected by surrounding lithology formation and closely correlated with mudstone content. When the thickness ratio of mudstone in the surrounding strata is less than 0.5, the hydraulic conductivity of KCC is more likely to be permeable. This observation of the mudstone thickness ratio provided here can be used as a criterion to qualitatively assess the hydraulic conductivity of KCCs.