“Raise Caving” – Cheaper and more flexible mining at great depths

Mass-mining methods, such as block caving or sublevel caving, enable low-cost and efficient mineral extraction, but these methods are associated with high capital cost and risks. Latter mining methods call for mine planning and decision many years in advance. Moreover, block caving and sublevel caving are difficult to apply in at great depths due to the high prevailing stress conditions. Additionally, a lack of flexilibity makes it very difficult to adapt the mine layout and mining sequence to mining experience and prevailing conditions, once development of the mine has started. Scientists of the Chair of Mining Engineering and Mineral Economics at Montanuniversität Leoben in cooperation with the Swedish mining company LKAB address these problems and develop a new mining method.

Block caving and sublevel caving have in common that rock mass caves during the extraction of the ore body in a controlled way. As a result regional stress changes, the formation of considerable abutment stresses, large-scale subsidence and significant seismic energy releases occur. Experience shows that these rock mechanics effects become especially critical at great depths as well as in strong competent rock masses. In order to address latter issues the new mining method “Raise Caving” was developed.

A further disadvantage of currently applied caving methods is their very long development time. It could take up to 15 years, until production starts. “Raise Caving” addresses also this shortcoming by enabling shorter ramp-up times until production. Furthermore, “Raise Caving” provides a good flexibility. Overall, the new mining method facilitates or enables a safe, low-cost and efficient extraction of deposits, particularly at great depths.

The new method is applicable at great depths, more flexible and cheaper

In “Raise Caving” the deposit is initially de-stressed with de-stressing slots developed from raises. Substantial pillars separate neighboring slots in order to control stress magnitudes and seismicity during de-stressing. The slots provide a stress shadow for production infrastructure, so that stoping can take place in de-stressed ground. As mining progresses, pillars are extracted and hangingwall is allowed to cave. “Strategic de-stressing of the deposit in combination with the application of raises enables a safe, as complete as possible and low-cost mineral extraction, particularly at great depths, where the control of rock pressure is decisive.”, explains Tobias Ladinig of the Chair of Mining Engineering. “The application of raises offers further, considerable potential, for example a rapid and efficient undercutting of the deposit or improved possibilities for controlling the caving direction.”

The new mining method has been developed jointly with the Swedish mining company LKAB. LKAB operates in Kiruna one of the largest and most modern underground mines worldwide. A joint research and development project, which includes a “Raise Caving” test site in Kiruna mine, is ongoing.

More information

Dipl.-Ing. Tobias Ladinig
Chair of Mining Engineering and Mineral Economics
T: +43 3842 402 2010
M: +43 664 80898 2010

© Fredric Alm/Alm & ME AB

Overview of “Raise Caving” and its main elements

Application of “Raise Caving” in a steeply-dipping, tabular, thick deposit

“Integrated Raise Caving” as an alternative for block caving