Sraj Banda disputerar vid LTU

PhD-student/researcher: Sraj Umar Banda

Title of doctoral thesis: Caving Mechanisms for a Non-Daylighting Orebody

Room: E246

Summary:

Sublevel caving is a highly efficient underground mining method, but has the distinct disadvantage of requiring the surrounding rock to fracture and cave. As a result, mining-induced deformations and caving eventually develop on the ground surface above orebodies extracted with sublevel caving. From this follows that any existing infrastructure on the ground surface must be relocated as not to be affected by the mining-induced deformations. This thesis examines the mechanisms of caving above non-daylighting orebodies mined with sublevel caving — i.e., cases in which there is a cap rock between the ground surface and the top of the orebody. The mechanisms of caving in a cap rock are comparatively less well known, in particular when and how caving breaks through to the surface. An increased understanding of the mechanisms leading up to surface caving and deformations are crucial to be able to plan for infrastructure relocation accordingly.

 

The thesis comprise work on (i) rock mass characterization to understand the mechanical behavior of the rock mass and the possible factors governing cave mechanisms, (ii) numerical stress modeling to understand stress changes and their effects on the rock mass behavior, (iii) discontinuum numerical modeling to quantify the influence of large-scale geological structures on the cave progression, and (iv) discontinuum cave modeling to more explicitly simulate probable cave mechanisms in the cap rock. The work has a strong application to the LKAB Malmberget Mine, and particularly the Printzsköld orebody, for which cave break-through will have significant effects on the central areas of the Malmberget township. The thesis has examined the use of both conventional and more novel modeling techniques to understand various aspects of the caving mechanisms. The work also comprises a developed methodology for using seismic information to interpret the progression of caving in the cap rock, which allows for more precise follow-up and prediction of caving.