Critical Issues of Ore Flow for the Raise Caving Method

Ore flow has been identified as one of the critical points of developing the novel mining method Raise Caving (RC). The focus of this contribution is on the key issues of ore-flow and on how to encounter them to enable a safe, efficient, and economic mining operation. In the de-stressing phase of RC, narrow, tabular de-stressing slots are developed via raises, only the blast swell is drawn, and hence they stay filled with blasted material at all times to support the hanging wall in order to prevent early caving and dilution ingress. To simultaneously enable a free surface at the top for blasting, the extracted amount from the bottom needs to be monitored consistently. Another point in the narrow de-stressing slots is to prevent hang-ups by an adequate slot thickness. Hang-ups in higher zones are especially critical as they are difficult to resolve and may lead to unnoticed hanging wall caving. In the following production phase, production stopes are developed in the de-stressed area behind the slots. During this phase, the stopes are always filled with blasted material as a support for the hanging wall. They are only drawn-empty at a later point after the stopes are fully established. The most important issue for production stopes is to prevent early dilution in order to extract the deposit economically. Additionally, the free surface needs to be prepared for upcoming blasts. To optimize the extraction, a uniform flow towards the draw-points needs to be created. The mentioned points can be addressed by a proper mine design and draw strategy. The parts of the mine design include the draw-point spacing, the draw-point position, and the draw-bell layout. Further on, the draw strategy must enable a uniform draw, guide the ore down the inclined stope, and prevent early dilution. The critical points mentioned in this contribution are approached by the R&D with empirical, numerical, and analytical means.