Numerical Analysis of Hanging wall and Footwall Deformation with Backfill : Parametric Study and Calibration Insights from the Kiirunavaara Mine

This thesis is based on a numerical analysis conducted using the RS2 software focusing on how backfill affects ground deformation. Ground deformation is a critical challenge for LKAB, as they aim to minimize its impact on the hanging wall, where the city is located, and the footwall, where the infrastructure is positioned. The goal of the study is to evaluate how backfill influences ground deformation from both positive and negative aspects, and to analyse the importance of different parameters when calibrating the model. The study takes up previous research and uses both empirical and numerical methods to understand how backfill affects the stability of the hanging wall and footwall. The model is created by using a two-dimensional program called RS2, where the design was done to closely resemble real conditions in the mine. To achieve this, earlier research was used as a foundation, and numerical simulations were calibrated against real GPS-data from the mining area. Both the mining and backfill processes were modelled to mimic real-world applications. A large amount of data from previous studies was used to ensure realistic results. The study highlights the importance of Young’s modulus and Poisson´s ratio as key factors in model calibration, as well as difference in deformation at different mining depths. The results show that backfill reduces deformation in the hanging wall by increasing the break angle, which helps decrease ground deformation. However, backfill has a negative impact on the footwall, where deformation increases by approximately 2 cm when backfill is applied to the crater, making it more challenging to minimize ground deformation in the footwall. The study also highlights that deeper mining increases stress and changes deformation patterns, requiring higher precision in the model and future research. Finally, the report provides recommendations for future work, including the need to study the long-term stability effects of backfill and to conduct additional analyses using alternative software to either validate or improve the results. The study offers valuable insights and methodological improvements to increase the safety and manage ground deformation effectively during sublevel caving.