Grinding mills are large rotating cylindrical steel vessels used to grind ore and minerals into finer particles. The mills are important parts of the mineral enrichment process and the grinding is the last step of the comminution process, where the particle size is reduced by a combination of abrasion and impact.The rotation of the mill under loaded conditions can result in fatigue cracks. Fatigue cracks and associated failures have been identified as a major problem in mineral processing plants. The cracks lead to unpredicted and unplanned production stoppages for inspections and for repair and replacement of the cracked mill parts. This leads to increasing costs due to production loss, additional man-hours and spare parts.The purpose of the research presented in this licentiate thesis was to calculate the structural strains, stresses, displacements, etc. in grinding mills in operation, to prevent overloading, to calculate crack propagation speeds and critical crack lengths, and to develop new improved mills that would withstand the current loading. This research has also aimed to propose, develop and test methods for the detection and monitoring of fatigue cracks in mills during operation, in order to facilitate optimal maintenance decision-making based on current crack sizes.The performed research is a case study of the secondary pebble mills of LKAB, a mining company in northern Sweden. The mills are situated inside dressing plants KA1 and KA2 in Kiruna. To achieve the goals, a number of crack detection and monitoring methods were investigated and evaluated as to their ability to find and monitor fatigue cracks on the running mills. Measurements with wireless strain measurement equipment, infrared thermography and crack propagation sensors were performed on the mills in operation.A finite element model of a mill was developed to calculate the strains and stresses in the mill at any position in the mill and for any loading condition. A variety of spatial discretizations, boundary conditions, material properties and loading alternatives were considered to simulate the behaviour of the real mill in the best possible way. To calculate the loading on the mills in operation, a mathematical model and computer software were developed to calculate the charge configuration, as well as the loading and the magnitude and distribution of the forces acting on the mill in operation. Using the finite element model and the computer software, the global displacement field of the entire mill structure was calculated using quasi-static loading for different inputs of the charge and process parameters.To verify the finite element results, the measured strain ranges for one complete rotation of the mill were compared with the corresponding calculated ones. The numerical results were also verified with logged process data, such as bearing reaction forces. One conclusion, based on the comparisons, is that the developed finite element model and the developed software tools can be considered useful for engineering applications.The developed software tools, together with the finite element model, make it possible to calculate the global displacement field of the entire mill structure for any situation. This is achieved by inputting the desired process data and charge parameters into the software, calculating the loads and force distributions, exporting them to the finite element model, and running the simulation. From the global displacement field, strains, stresses, reaction forces, displacements, etc. can be calculated with standard routines for any position in the mill.The performed research work gives a deeper understanding of the field of structural analysis and load calculation of grinding mills in operation. The complexity of modelling the behaviour of mills in operation is high. Consequently, it is difficult to obtain accurate estimations of crack propagation speeds and critical crack sizes based on the calculated stresses.It has been found that strain measurements, with strain gauges attached to the mill mandrel, can be used to detect and monitor larger circumferential cracks near the flanges in the mill in operation, since the measured strain ranges increase with the crack size. It has further been found that infrared thermography can be used as a method to indicate cracks without stopping the mill, as the increased thermal gradient around the cracks can be detected by a special type of thermal instrument.Crack propagation sensors have proven to be ideal for high-precision online monitoring of the crack propagation of smaller cracks at the corners of the manholes in the mill. Finally, it has been found that strain measurement is a useful method not only to verify finite element results and to detect and monitor cracks, but also to prevent overloading of the mill and to estimate charge features such as the filling level, the charge shape and the position of the charge circumferentially inside the mill during operation.

The increasing mining depth leads to higher stress magnitudes, resulting in increased seismic activity and more seismically-induced damage. The effectiveness of the ground support system under dynamic loading conditions has therefore become of prime interest to the mining companies in order to provide safe mining conditions with a minimum of production disturbances caused by unstable infrastructure. The problems of mining-induced seismicity have necessitated the use of ground support systems which are capable of withstanding strong dynamic loads. Although there are large amounts of measurement data from the site-installed seismic systems, they cannot be used directly to design and select the appropriate support systems due to lack of control over the location and nature of the seismic source and the effect of the rock mass on the seismic waves. Large-scale tests using explosives as the seismic source have therefore become a useful method to evaluate the performance of rock support systems for seismic conditions. A series of seven large scale dynamic tests of rock support was conducted in the Kiirunavaara mine. Explosives were detonated in boreholes in the pillar between two cross-cuts in order to generate a dynamic load on the rock support system installed on the cross-cut wall. This was done with the aim to develop a testing methodology for in-situ testing of ground support. Furthermore, the response of the installed support system to strong dynamic loading was also evaluated. The tests included ground motion measurements, fracture investigation, ground and support motion imaging, as well as the deformation measurements. The results of the measurements in Tests 1 to 7 are presented and the methodology used to design the tests is discussed. The results indicated that the relation between the burden distance and the used amount of explosive material and number of blastholes has a vital role in either reducing or involving the effect of detonation gases in test results. The large amount of data recorded during these tests will be useful for the calibration of more advanced numerical models. The energy absorption by the Swellex Mn24, 100 mm fibre reinforced shotcrete (40 kg/m3 steel fibre) and 75 mm x 75 mm weld mesh with 5.5 mm diameter was estimated and compared to that obtained from the large scale in-situ tests and laboratory tests conducted in different countries. The comprehensive ground motion data provided for the whole test wall was used to estimate the kinetic energy transmitted to the fractured zone where the support system was installed.

A railway is an energy efficient mode of transport as it uses the low resistance contact between wheel and rail. This contact is not frictionless and causes wear on both surfaces. The wheel-rail guidance is made possible by the shapes of wheel and rail profiles. To increase revenue for train operators and decrease cost for railway infrastructure owners, there is a need to monitor the conditions of the assets. A major cost-driver for operators is the production loss due to wheels, especially from maintenance costs when changing and re-profiling wheels.The research in this study has been performed on the Iron Ore Line (malmbanan) in northern Sweden and Norway. Large parts of this railway line are situated north of the Arctic Circle with temperature variations from -40◦C to +25◦C and a yearly average around freezing. Running trains in this environment strains all components. The purpose of this research is to evaluate how condition-based maintenance should be implemented for railway wagons. Research methods include a literature review, interviews, and data collection and analysis. Manual wheel profile measurements have been combined with maintenance data, weather data and wheel-rail force measurements to make comparisons between seasons and wagons.The analysis shows that there are different lateral force signatures at the wheel-rail interface dependent on the wheel’s position within the bogie. It also shows the need to change both wheel sets of the bogie simultaneously. Finally, it proves there is greater wheel wear at low temperatures.

In open pit mining, it is important to know as much information as possible about rock masses to be mined for more cost-effective mining operation. In rock engineering perspective, information about rock mass characteristics usually includes hardness of the rock, geological features, fractures, faults, ore contacts, water bearing stratum. The information about large scale rock mass characterisation is still based on traditional methods such as widely spacedcore drillings, geological mapping of exposed walls, analysis of drill cutting, etc but these methods involve uncertainty about rock mass characteristics in uncored areas. In addition, they are expensive and time consuming. The need for more inexpensive methods providing high resolution rock mass characterisation over large mining areas is therefore a priority forfuture mining industry. Measurement While Drilling (MWD) is a well-established drill monitoring technique which provides information about the rock mass in each production hole. This technique is inexpensive and also ensures high resolution information. By using this technique, drill parameters such as penetration rate, feed force, rotation speed, rotation torque and air pressure are recorded during production drilling which can be used to characterise the penetrated rock mass. However, recorded parameters are not only influencedby the variation of rock mass characteristics; they are also affected by the operators, rig control system interventions, bit wear and measurement errors. In order to use this large amount of data on recorded parameters for the purpose of rock mass characterisation, it is necessary to improve our existing understanding about the contribution of all the influencingfactors and to develop the techniques for identifying and minimising the effect of those factors on rock mass characterisation. The focus of this thesis is to evaluate Measurement While Drilling (MWD) system as a tool for large scale rock mass characterisation in rotary blast hole drilling. In this thesis, researchmethods mainly include literature review, data collection, processing, integration, and analysis. The data have been collected from one of the operating open pit mines in Sweden. Multivariate analysis has been performed to assess the wear of the bit. This thesis presents an attempt to evaluate recorded penetration rate and calculated specific energy for rock mass characterisation. Penetration rate is considered as resistance to crushingof the rock while the calculated specific energy is taken as an index of the mechanical efficiency of a rock working process. The analysis shows that horizontal maps of penetration rate and specific energy (hole average) value reflects the variation of rock mass characteristics in a bench. The areas in the bench which have comparatively higher penetration rate and lower specific energy reflect possible interaction between the bit and soft or weak rock orheavily jointed rock. In contrast some areas in the bench have a relatively lower penetration rate and higher specific energy, indicating possible interaction between the bit and hard rock. In addition, using penetration rate and specific energy values between two subsequent benches indicate similar boundaries among the penetrated zones. When plotting specific energy against penetration rate in each bench, a clear inverse non-linear relationship has beenfound between those parameters. This correlation indicates that penetration rate and specific energy can indicate rock mass behaviour. Further, statistical analysis is done to observe the statistical significance of penetration rate and specific energy values among the different penetrated areas in the bench. The results indicate that penetration rate and specific energy can be used for characterizing large scale rock masses. In addition, information about the rockmass in the upper bench can possibly be used in the next bench to improve production planning. However, hole by hole analysis shows penetration rate and specific energy are influenced by bit wear, hole depth variables, flushing system, operator influence, drill control system, etc.Principal Component Analysis (PCA) shows that penetration rate and specific energy reflecting the change of rock mass characteristics basically are not correlated to bit life length. The bit life length seems instead to be well correlated to the operational parameters such as rotation torque, rotation speed and to a minor extent feed force. Conclusions from PCA analysis must be conservative since the explanation rate for the first two components islimited to 56.5%. Further, the analysis shows that recorded penetration rate has a negative trend with the increasing hole depth. The calculated specific energy has a positive trend with the increasing hole depth. This means that recorded parameters are influenced by hole depth variables.The flushing system also influences recorded parameters. The analysis shows that constant air pressure from the collaring point to the end does not give a clear indication of better flushing system as frequent joints and regular water ingression usually cause fluctuation of pressure.Some of the above mentioned problems can be handled to minimise the effect of influencing factors on recorded parameters. The direct effect of bit wear and hole depth dependency can be minimised by generating a horizontal map of recorded data (e.g. penetration rate) over a large area in the bench. Hole depth dependency on recorded parameters can also be neutralised by performing normalisation based on a regression line using simple geometry. Inshort, the effect of influencing factors on the recorded parameters obtained by using the Measurement While Drilling technique can be minimised and, this technique, in turn, can become a useful tool for large scale rock mass characterisation.

The application of discrete event simulation for the optimization of the haulage methods of underground operations at great depth is presented. The discrete event simulation was carried out to evaluate four haulage methods for the improvement of the overall mine production and a minimizing of the operating costs. Other techniques can be applied to achieve the same objective but discrete event simulation is known for its advantage of more accurately accounting for real world uncertainty and diversity. Discrete event simulation is then combined with mixed integer programming to improve decision-making in the process of generating and optimizing the mine plans associated with each hauling option. The haulage system is one of the most important operations in underground mines as it involves the transportation of the mined out material from the draw points to the processing plant. When the depth increases, hauling of ore from deeper levels need to be evaluated in order to account for the constraints, configuration and current utilization of the ore handling system for improvement of productivity and operations. The increase in mine depth affects many factors among which are the increases in haulage distance from mine areas to the mine surface. The increase in haul distance results in an increase in the energy cost of the specific hauling equipment. The haulage process is one of the most energy-intensive activities in a mining operation and thus one of the main contributors to energy cost. This research uses the combination of discrete event simulation and mixed integer programing to compare the operating values of the mine plans generated for an orebody at depth levels of 1,000, 2,000, and 3,000 meters for diesel and electric trucks, shaft and belt conveyor haulage systems for the current and future energy prices.The results shows that, in comparison with analytical methods, discrete event simulation combined with Mixed Integer Programming (MIP) is faster and generates a more feasible solution, increases the understanding of the behavior of various systems, and reduces risk when selecting the operational systems. It is indicated that the energy cost increases as the mine depth increases and it differs for each haulage method for both current and future energy prices with higher costs in diesel trucks and lowest costs when using a shaft haulage system. The energy costs for diesel trucks account for 38.2%, 46.8% and 63.1% of operating costs at the current energy price, and 64.9%, 72.5% and 83.7% of operating costs at the future energy prices at the 1,000, 2,000 and 3,000 meter depth levels respectively, while the energy cost for the shaft haulage system accounts for 10.8%, 13.0% and 15.4% of operating costs at the current energy price, and for 26.6%, 30.9% and 35.4% of operating costs at the future energy price at the 1,000, 2,000 and 3,000 meter depth levels respectively. The energy costs is further analyzed based on haulage costs as a percentage of the total operating cost for all options, and the results show that diesel truck haulage is substantially more expensive compared to other haulage options with least energy cost on shaft haulage system with increasing depth. This study thus provides mining companies operating at great depths, a broad and up-to-date analysis of the impact on energy costs on the haulage methods as the mine depth increases.

The Luossavaara-Kiirunavaara Aktiebolag (LKAB) Kiirunavaara mine is a large scale sub-level caving (SLC) mine in northern Sweden. The use of SLC as a mining method inherently causes significant rock mass movements above the extraction level. It has been one of the objectives of LKAB since the early 1990s to accurately forecast the global stability of the footwall in relation to the inherent rock mass movements from the sub-level caving. In the Kiirunavaara case, the dip of the main ore-body entails the footwall to develop as a rockslope confined by cave material from the hangingwall. It has been discussed that the global stability of the footwall is likely related to the interaction of two or more failure mechanisms acting in combination, however, the true footwall failuremechanisms are still debated. The objective of this thesis is to study and evaluate the footwall behaviour and determine the predominant mechanisms by combining data from field observations, numerical modelling and seismic data analysis. Field data was collected through damage mapping on decommissioned levels in the footwall on depths between 120 to 700 m for the full 4 km ore-body length. From the mapping data a conceptual boundary between damaged and undamaged footwall rock was established in the form of a damage boundary surface. The 3D geometry of the damage surface was analysed and a section was extracted and used in calibrating numerical models for simulatingthe footwall behaviour in response to mining. A parametric study was performed to highlight high impact inputs and study plausible origins of the conceptual damage surface. A base case model was adopted to explain the failure evolution and used in the analysis of seismic data. The seismic data was analysed with respect to origin mechanisms as well as temporal and spatial location patterns. The outline of the large scale footwall fracturing interpreted from the conceptual damage surface was geometrically complex. No single principal failure modes could be identified from evaluating the 3D geometry favouring the initial assumption of multiple mechanism interactions. In addition, the mapping data itself indicated changes in failure mode with respect to depth. On higher levels structurally controlled damages were predominant while general rock mass failures became common on lower levels. The parametric study related thehighest influence on plastic response to the internal cohesion followed by internal friction angle. This was interpreted for the base case as the rock mass being more sensitive to shear failures in favour of tensile failures. This indication was further strengthened by the evaluation of the seismic data. The origin analysis of the seismic events pointed to a significant dominance of shear origin events clustered in active fracturing volume indicated by the base case numerical analysis. By combining field observations, numerical modelling and seismic analysis a plausible description of the large scale footwall fracturing could be provided. The structurally controlled failures in the upper and mid portion of the footwall are reactions to active failure on deeper lying levels. Active fracturing of the footwall rock mass occurs based on the numerical and seismic results on levels on and underneath the current mining level. On the levels where active fracturing takes place the rock mass is confined by the support pressurefrom the un-mined ore-body. As mining progresses deeper the confinement is lowered as the ore is replaced by low stiffness cave rock. Due to the loss of support pressure the rock mass expands towards the sub-level cave and the induced weaknesses are activated and manifested as drift damage during rock mass mobilisation. The numerical models showed that the mobilised rock mass above the mining level exhibits the displacement pattern of a potential curved shear failure. This failure path intersects both the footwall slope face and thestructures from the upper footwall and thus enables these structures to shear.

The expansion of economic activities and increasing mobility of people on short, medium and long distance trips is an issue that requires attention in the transport industry. The need to address this demanding issue in a sustainable and economically efficient way is the core of general capacity challenge in railway industries. This informs the strategic objective of ensuring an efficient and competitive mode of transportation by many infrastructure managers including Swedish Transport Administration. An aspect of railway infrastructure management which is promising for the enhancement of existing infrastructure capacity is the improvement of maintenance process. The frequency of traffic interruption due to infrastructure failure, reduction of functional performance due to infrastructure degradation and length of track possession time are incidences limiting operational availability of railway infrastructure and capacity thereof. Achieving the goal of supporting the inherent capacity of existing railway infrastructure requires implementation of effective & efficient practices for large and small impact maintenance tasks. This research has addressed the above mentioned concerns by studying the opportunities which maintenance presents towards enhancing the capacity of existing railway infrastructure. Outsourcing aspect of maintenance organisation has been studied and a conceptual framework to facilitate the implementation of performance based maintenance contracting is proposed. This will enable the achievement of quantity and quality requirements of traffic performance. Furthermore a risk assessment procedure has been presented to identify bottlenecks restricting the capacity on any line and also for continuous improvement has been suggested. A model for planning and scheduling of tamping action has been presented. This will lead to reduced track possession time and minimum cost of intervention while geometry quality is kept at desirable level. Case studies on the above procedures and model have been presented to demonstrate their application for maintenance improvement.The outcome of this study is development of effective maintenance principles that should serve as basis for maintenance improvement programme to support reliable and inherent capacity of existing railway network. This improvement covers organisational and technical performance, all enhancing the possibility to increase the capacity of railway network.

The railway is an important mode of transport, due to its environmental friendliness, high safety level, and low energy consumption, among other reasons. Railways provide a sustainable means of transporting a large amount of freight and passengers, in a cost-effective and comfortable way. The railway system has a large number of stakeholders and a small improvement in the system will give many advantages, including financial savings and an increase in the quality of service. The Swedish railway network is old and there has been almost no expansion of the network during the past few decades. There is currently a demand for more track capacity and there are no more tracks availably at the network; therefore, the existing network is expected to deliver more capacity.The railway operators are the largest cause of train delays and wheel failures are one major contributor of the delays caused by operators. The infrastructure manager is the second largest owner of train delays, and a large contributor of their train delays is switches and crossings (S&Cs). This thesis shows proposals for how condition monitoring technology can be used more efficiently for both the infrastructure and the rolling stock to increase the reliability of their critical items by decreasing train delay. Firstly, the condition of the wheel-rail interface is important, in that a bad wheel influences the rail and vice versa. The monitoring of rail profiles is already in use, but the monitoring of wheel profiles is still in the development phase. This thesis shows the performance of a wheel profile measurement system (WPMS) for an extreme climate, and a case study of performance measures such as the accuracy and reliability of the system is presented. An additional topic dealt with is how the information from the WPMS can be combined with that from the wheel defect detectors to find early indications of wheels with bad behaviour. Secondly, the S&C is an essential component of a railway system in that it increases the flexibility by diverting traffic, but S&Cs need adequate support to work properly. A camera-monitoring method for S&Cs is presented which increases the inspection frequency and decreases the human activities on the track and the train delay. In conclusion, this thesis shows that the WPMS investigated works well with a high level of performance concerning measurement accuracy and reliability in an extreme climate, and that there is still some potential for improving the system. The combination of the WPMS and wheel defect detectors shows that wheels with a high flange height have a higher probability of ending up as wheels suffering from failures. A new maintenance limit for the flange height can reduce the number of wheel defects on the track. Camera-monitoring of the S&C will increase the availability and reliability of this item and even reduce the time on the track required for the maintenance action “check” through fewer inspections and maintenance actions. These proposed monitoring techniques can improve the railway system reliability by reducing the consequential train delay times, by decreasing the number of failures of wheels and S&Cs.

Railway traffic has increased over the last decade and it is believed to increase further with transportation shifting from road to rail, due to rising energy costs and the demand to reduce emissions. To manage railway infrastructure assets effectively against agreed-upon and set objectives, performance must be measured and monitored. Different systems are used to collect and store data of traffic, failures, inspections, track quality, etc., for subsequent analysis and data exchange. Performance indicators (PIs), e.g. for RAMS (reliability, availability, maintainability, safety), are continuously developed to support infrastructure managers (IMs) in identifying performance killers in order to make efficient and effective decisions. However, they are often ad hoc and seldom standardised. Moreover, the use of standards and the need for harmonisation of railway operations have grown with interoperability, e.g. building of a trans-European railway network. The~efficiency and effectiveness of railway infrastructure can be improved if an appropriate performance measurement (PM) system is identified and specifically developed. In traditional PM systems, PIs are given threshold values, indicating when an action needs to be taken, i.e. they can to some extent be reactive. Also, PIs are often aggregated measures, which can make them abstract. By this trend in transportation and shortcomings in performance measurement, there is a need to improve the strategic planning and measurement of performance for more proactive decision making and future standardisation.In this research, a link and effect model for performance improvement of railway infrastructure is developed. It provides a continuous methodology for breaking down objectives into operational requirements and linking them to results, using performance indicators, and algorithms for data analysis and simulation, for decision support.Keywords: railway infrastructure, performance, RAMS, maintenance, dependability, indicators, link and effect, decision support / Link and Effect Model for Maintenance of Railway Infrastructure

The interaction of the geological and mining environments leads to a variety of forms of rock mass behaviour, including seismicity and falls of ground. A precise understanding, however, of the role of geology in rock mass behaviour experienced by Luossavaara-Kiirunavaara Aktiebolag’s (LKAB) Kiirunavaara Mine remains unknown.Since late 2008, the sublevel caving mine regularly experiences induced seismicity (Dahnér et al., 2012). Seismic events occur in the footwall, orebody, and hangingwall. Instabilities, sometimes related to specific seismic events, are unevenly distributed throughout the rock mass. Failure mechanisms of these instabilities include structurally controlled failure (sometimes as shake down), strainbursting and spalling, which are typically a result of local stress changes. Occasionally, these falls of ground are rockbursts; violent ejections of rock causing damage to infrastructure and/or personnel that are caused by remote seismic events.Some previous work has been done at the Kiirunavaara Mine for both specific events and specific volumes to better understand the rock mass behaviour (see e.g., Sjöberg et al., 2011, 2012). However, the causes of the uneven distribution of both seismicity and instabilities at the mine are not understood, particularly at the mine-scale. As part of a larger Ph.D. project, this study explores the role of geology in the mine-scale behaviour at the Kiirunavaara Mine. This is done through two approaches: 1) exploratory numerical stress modelling, and 2) development of a geomechanical model of the rock mass.The exploratory numerical modelling of the mine evaluated common assumptions made by researchers and consultants when completing numerical stress modelling of this orebody. A previously estimated virgin in situ stress state was applied in a 3-D model developed of the nearly 5 km long orebody and surrounding host rock. The model had definition between footwall, ore and hangingwall materials. Run as a continuum for this analysis, the stresses from the elastic and perfectly plastic models corresponded to stresses recently measured in situ at two sites using overcoring, indicating that the estimated virgin stress state is consistent at depth. Alternating two commonly used perfectly plastic material properties for the footwall significantly influenced the location of plastic failure throughout the rock mass, including in the hangingwall. A physical alignment of plastic failure from the models and mine seismicity for the entire rock mass was not found for the individual cases. Large magnitude shear events tended to be external to plastic failure. The difficulties relating plastic failure to seismicity can be associated with a number of causes, including that the rock mass characteristics were too simplified (for example, no discontinuities were included, the only geological units included were the footwall, hangingwall and orebody, etc.) to represent the rock mass behaviour.A geomechanical model of the rock mass is needed to better understand characteristics of the rock mass, in addition to those included in the stress models, which may be of importance to behaviour. Due to a complex, heterogeneous and clay-altered rock mass, a new methodology was developed to create a geomechanical model. The methodology is based upon standard statistics, geostatistics, and an extension of previous quantitative domaining work. Clay volumes (represented by a model based on borehole data calibrated to underground mapping) correlated to the geomechanical characteristics and behaviour of the rock mass. The rock mass in the immediate vicinity of the volumes of clay alteration had lower RQD values, more random jointing, and a higher concentration of falls of ground than the surrounding rock mass. The correlation between the geomechanical model and the falls of ground lead to the development of a new conceptual model of some of the mine-scale rock mass behaviour, in which the clay volumes play a significant role in stress redistribution.The understanding developed through this study has laid the framework for future analysis of a more advanced and complex nature. Numerical stress analysis will be used to test the conceptual model developed and further analyze the relationship between geology and mining, with the intention of improving the understanding of the causes of rock mass behaviour. This improved understanding has the potential to aid with selection of production planning alternatives for risk mitigation, not only for the Kiirunavaara Mine, but for other highly stressed, hard rock environments.