70 years of investigation on Karst collapse column in North China Coalfield:cause of origin,mechanism and prevention

The history of studying the Collapse column in North China Coalfield and the great achievement achieved so far were reviewed in a comprehensive way. During 1930s, the scenario of Karst Collapse column was discovered accidentally in coalfields under mining process. Because of the impact that this scenario has on mining operation and its safety, more and more extensive research was carried out on it. Right after the P.R. China was founded, energy production was put in high priority among many other urgent sectors and the impact of collapse column on coal mining had unveiled gradually. As researchers and engineers solved the technique issues on scene, the fundamental theory behind also gained rapid development. In 1984, the severe water inrush of large collapse column taking place in Fangezhuang Mine of Kailuan coal mine area shocked the world, however the consequential success on sealing and recovering had exhibited the progress on such technique in China; this incident has been a indisputable hallmark on handling such issues in China. Afterwards, the energy industry has gone through from down turn to the golden era of ten years of booming; coal mining depth has became deeper and deeper, and tendency toward west region of China, which is accompanied with higher and higher threat from water inrush of collapse column. As emergence of new theories and technologies, along with the continuous extensive development on related researches, the fundamental theories and handling technique have been perfected. However because of the locality and lack of generality of the issue, we could only reference to theories developed oversea on Karst collapse and mining. This paper comprehensively summarized basic characteristics, distribution law, genetic mechanism, water conductivity, water inrush mode and mechanism, prediction exploration and management; also clarified spatial morphological and filling characteristics; revealed features and structural features of Karst collapse column; systematically analyzed the different classifications and types of Karst collapse columns; discussed the water conductivity of Karst collapse columns, established a prediction index system and prediction model for Karst collapse columns, and proposed the water inrush modes and mechanisms of the collapse column with mechanical criterion. The feasibility of the prediction of water inrush quantity from the collapse column is also explored along with the formalizing and standardizing the procedure of predicting exploration and treatment of the collapse column. One of this work's objectives is to summarize all the available treatment techniques of the collapse column. In this work, authors also point out some existing problems in the current research on collapse column, and refine scientific propositions on the Karst collapse column's genesis, water conductivity, prediction, water inrush mechanism and water inrush quantity forecast. By listing all the challenges confronting us on techniques such as fine exploration of the collapse column, the monitoring and forecasting of water inrush, and the management equipment technology, authors in this work tried to lay out the direction for future research and technique progress. At the end authors conclude that even with the great success that had been achieved on this issue so far, we are still far away from satisfactory theoretical and technical system capable of assuring safe production in mines.