Doctor Educationis / Recent research has highlighted the importance of cut-and-fill cycles in valley-bottom wetlands. This study considers the impact of longitudinal and lateral sediment connectivity on the natural recovery potential of valley-bottom wetlands. Pietersielieskloof is a Prionium serratum (commonly known as palmiet) dominated discontinuous valley-bottom wetland. P. serratum is considered to be a peat-forming ecosystem engineer that enhances sediment infill in valleybottom wetlands. Due to its ecological importance and potential as a carbon store, this wetland has been earmarked for rehabilitation by Working for Wetlands. The study ascertains the importance of including sedimentological and geomorphological input in wetland rehabilitation and management strategies. A study of wetland geomorphology was conducted to develop an understanding of the natural dynamic of cut-and-fill processes as context for recent erosion and deposition events. Sediment samples from gully walls and cores were collected for organic content and particle size analysis and five sediment samples predating the current phase of erosion were radiocarbon dated. The valley form was surveyed using cross-sections and long profiles, and historical change was digitised using 30 m – 5 to 30 mm resolution aerial imagery from 1938-2016 in ArcMap.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In the mining industry, the mining cycle is a very important part in the operating stage of every mining unit. Through the exploitation method used, the mining cycle provides mineral ore, which subsequently undergoes various metallurgical processes and its commercialization and thereby generates profits to the mining company. Currently, within this cycle, the hauling and transportation stages are those that have a lower efficiency with respect to the drilling and blasting stages. Therefore, the sector is always seeking effective ways to optimize these processes, reduce downtime and increase productivity. Six Sigma is a technique that allows for the continuous process improvement. In this study, the factors that generate inefficiency in the hauling cycle are determined, and alternatives are implemented to solve the main problem and improve the operations cycle.

Underground mining is a complex operation that requires careful planning. The short-term scheduling, which is the scheduling of the tasks involved in the excavation process, is an important part of the planning process. In this master thesis we propose a new method for short-term scheduling of a cut-and-fill mine operated by the mining company Boliden AB. We include a new aspect of the problem by incorporating a priority between the excavation locations of the mine. The priority feature allows the user to control the output of the scheduling and to direct resources to the locations where they are most needed according to the long-term plans. Our solution method consists of two components: a constructive heuristic method that construct a complete solution by solving partial scheduling problems containing subsets of tasks, and a logic-based Benders decomposition scheme for solving these partial problems. The computational performance of the proposed method is evaluated on industrially relevant largescale instances generated from data provided by Boliden. Comparisons are made with applying a constraint programming solver on the complete problem and with replacing the logic-based Benders scheme by applying a constraint programming solver on the partial scheduling problems, respectively. Results show that the heuristic method combined with the logic-based Benders decomposition scheme outperforms the other two methods on all instances.

The optimization of production has come a long way in the last few years. From having to implement new production philosophies directly into the production, today you can simply build a simulation on the computer that can be used to test new solutions. This makes it cheaper and less time-consuming to improve production. This report will describe the thesis work made by two students from Lulea University of Technology studying mechanical engineering with orientation production technology. The thesis work was made at Boliden MineralsAB during the spring term of 2021. This master thesis aim is to look at the potential of using discrete-event simulation as a tool to test different production philosophies. To do this, a simulation model is built to represent Boliden’s mining operation. The focus will be on the Cut and fill process, and how vehicles and operators are dispatched. From interviews, videos and information gave by Boliden a current state analysis was done to get a good understanding of the situation and how the process works. This combined with a litterateur study a good foundation was made to start building the simulation. Since this is the first time Boliden uses simulation on the cut and fill process in this manner, there’s been close contact with Boliden to validate and verify the models. The different production scenarios that were simulated were selected with the guidance of Boliden to look at the most relevant areas for them. Firstly, a base model was constructed, this model had a number of restrictions compared to the real-life process. With data from previous work that Boliden had with simulation models, the base model could be controlled that it worked properly. From this model others, models could be build-up, with the difference of using another production control philosophy for the simulation. By using these philosophies there could be determined an increase by 1% in productivity when prioritizing operators to the bottleneck of the process to maximize utilization.