State-of-the-Art in Underground Coal mining and Automation Technology in the United States

Underground coal mining in the USA employs two methods: longwall mining and room & pillar mining. Mines with suitable geological condition and sufficient resevres generally use longwall mining, otherwise, room & pillar mining is used. Between 1994 and 2017, the number of underground coal mines in the USA fell by79%, to 237 in 2017. But output from individual mines has risen by 230%, and coal production is more concentrated and efficient. Longwall mining in the USA is mainly practiced in medium-thick seams, and the mining height is generally 1.6~2.5m (maximum height is 4.2m and minimum height is 1.2m). Multi-entry development, rectangular cross-section roadway and roof bolting are all adopted for panel development and roadway configuration and support. In recent years, panel dimensions, equipment power and size continue to increase, production system have become more reliable. Automatic of longwall mining began with the development of shield with electro-hydraulic control technique in 1984. Since then, the technology of single machine automation of shield, shearer, AFC and SISA system has been developed. After 2000, the technology of semi-automatic panel and remote control technology of shearer were developed. At present, the main application is semi-automated longwall face, only 2 panel faces have applied the remote control technology of shearer. These technologies have solved the problem of automated mining in panels with good conditions, but it still needs manual intervention in complex geological conditions. Research and development of key sensors and equipment for automatic mining to adapt to the change of geological conditions, the improvement of face-end operation, operation safety, the control of dust and noise, big data analysis, faster communications and visualization technologies are currently the key fields of research and development in the USA. In recent ten years, the process of room & pillar mining technology has not changed much. However, significant progress has been made in the development of related technologies such as automation, informatization and intelligentization of mining system.