Stress dependent flow behavior in sublevel caving mines

Sammanfattning

Sublevel caving is an underground mass mining method that utilizes the gravity-induced material flow for ore extraction. The granular flowbehavior is one of the main phenomena describing this mining method’s efficiency; therefore, a good understanding of the flow behavior is essential.The knowledge of the material flow behavior evolved in the late 1950:s when the mining method became more commonly used. However, due tothe complexity of the granular material flow, all parameters are not well studied, and a lack of knowledge still exists. With the increasing mining depths, higher stresses will occur inside the rock mass. How these increased stresses influence flow behavioris one of the parameters that are not well studied. Unfortunately, manipulating these is challenging in physical material models and mighteven be impossible in field experiments. However, achieving such control is possible using a discrete element method software. The model developedfor this thesis simulates pre-stressed rock mass up to 50 MPa and monitors the flow behavior in the software PFC3D. The result showed that the increased stress had the potential of causing a stable configuration of material inside the opening ring, known as a hangup.The hang-up later was destabilized when the blast continued to the next ring. For the chosen blasting geometry, the shape of the draw zone of thematerial that reached the extraction point did not seem to be affected by the stresses.