Classification of karst collapse columns in North China coalfields based on the generalized model of inside structure of the columns

Karst collapse columns are one kind of special geological structure in North China coalfields, threatening the safe coal production. In order to study the mechanism of water inrush in collapse columns, the generalized model of inside structure of the columns containing enrockment section, mud section, clast section and fracture section is put forward combining with the formation process through the enormous amount of research. And karst collapsing columns are classified into 8 types on the basis of the model, and the geologic characteristics of each type are analyzed and summarized. Suggestions to excavation engineering are also given for different types of collapse columns.