<p>WC/Co cemented carbide is a composite material for highly demanding wear applications. The unique combination of hardness (from the WC-phase) and toughness (from the binder Co) gives a material especially suitable for rock drilling. This thesis, investigates the deterioration and wear of these cemented carbide buttons and the correlation to different rock types.</p><p>To better understand the nature of the wear of the cemented carbide buttons, the counter surface –the rock- has also been studied. A range of important rock types has been investigated with respect to hardness distribution and scratch response in a micro scale and friction properties when slid against cemented carbides. </p><p>The cemented carbide may deteriorate due to a number of mechanisms. The effect of fatigue in the structure was studied in TEM and particle erosion response was used to probe the corresponding mechanical degradation. </p><p>Further, homing cross sectioning has been developed and used as a new technique to investigate the presence of weak zones in the surface layer of a drill button. It was found that rock penetration into this layer is a very common mechanism, with profound implications for the nature of the wear. </p><p>High resolution scanning electron microscopy has been extensively used to map the deterioration and wear of numerous drill buttons, worn against different rock types in different kinds of drilling applications. Finally, the collected data on the surface damage, the reptile skin formation, the rock intrusion and the properties of the rock are assembled into a new view of the deterioration and wear of cemented carbide in rock drilling. </p>

WC/Co cemented carbide is a composite material for highly demanding wear applications. The unique combination of hardness (from the WC-phase) and toughness (from the binder Co) gives a material especially suitable for rock drilling. This thesis, investigates the deterioration and wear of these cemented carbide buttons and the correlation to different rock types. To better understand the nature of the wear of the cemented carbide buttons, the counter surface –the rock- has also been studied. A range of important rock types has been investigated with respect to hardness distribution and scratch response in a micro scale and friction properties when slid against cemented carbides. The cemented carbide may deteriorate due to a number of mechanisms. The effect of fatigue in the structure was studied in TEM and particle erosion response was used to probe the corresponding mechanical degradation. Further, homing cross sectioning has been developed and used as a new technique to investigate the presence of weak zones in the surface layer of a drill button. It was found that rock penetration into this layer is a very common mechanism, with profound implications for the nature of the wear. High resolution scanning electron microscopy has been extensively used to map the deterioration and wear of numerous drill buttons, worn against different rock types in different kinds of drilling applications. Finally, the collected data on the surface damage, the reptile skin formation, the rock intrusion and the properties of the rock are assembled into a new view of the deterioration and wear of cemented carbide in rock drilling.

Modern mines require systems that quickly deliver backfill to support the rock mass surrounding underground openings. Cemented Paste Backfill (CPB) is one such backfilling method, but concerns have been raised about CPB’s liquefaction susceptibility especially when the material has just been placed, and if it is exposed to earthquakes or large mining induced seismic events. Conventional geotechnical earthquake engineering for surface structures is now relatively advanced and well accepted, and so the objective of this thesis is to consider how that framework might be extended to assess the liquefaction potential of CPB. Seismic records were analyzed for earthquakes and for large mining induced events. Important seismological trends were consistent for rockbursts and earthquakes when the signals were recorded at distances as proximate as one kilometre, suggesting that the conventional earthquake engineering approach might plausibly be adapted for such design situations. For production blasts and for more proximate locations to rockbursts, much higher frequencies dominate and therefore new design methods may be required. Monotonic triaxial tests conducted on normally consolidated uncemented mine tailings demonstrated that the material is initially contractive up to a phase transition point, beyond which dilation occurs. Most importantly the material never exhibits unstable strain softening behaviour in compression, and only temporary or limited liquefaction in extension. The addition of 3% binder results in initial sample void ratios that are even higher than their uncemented counterparts, and yet the material friction is slightly enhanced when tested at 4 hours cure. These results suggest that the flow liquefaction phenomenon commonly associate with undrained loose sand fills will not occur with paste backfill. Cyclic triaxial test results analyzed in terms of number of cycles to failure for a given cyclic stress ratio exhibited a trend consistent with previous tests on similar materials. However, the addition of 3% binder and testing at 4 hours cure resulted in an order of magnitude larger number of cycles to failure – a surprising and dramatic increase, suggesting good resistance of the material to cyclic mobility. Future research is recommended to build on these results and develop more robust methods for liquefaction assessment of CPB.

Cemented Paste Backfill (CPB) is a relatively new backfilling technology for which a better understanding of binder hydration is required. This research uses electromagnetic (EM) wave-based techniques to non-destructively study a CPB consisting of tailings, sand, process water and binder (90% blast-furnace slag; 10% Portland cement). EM experiments were performed using a broadband network analyzer (20 MHz to 1.3 GHz) in the lab and capacitance probes (70 MHz) in the lab and field. Results showed that the EM properties are sensitive to curing time, operating frequency and specimen composition including binder content. The volumetric water content interpreted from dielectric permittivity varied little with curing. Temporal variations in electrical conductivity reflected the different stages of hydration. Laboratory results aided interpretation of field data and showed that a reduction in binder content from 4.5% to 2.2% delays setting of CPB from 0.5 days to over 2 days, which has important implications for mine design.

Cemented Paste Backfill (CPB) is a relatively new backfilling technology for which a better understanding of binder hydration is required. This research uses electromagnetic (EM) wave-based techniques to non-destructively study a CPB consisting of tailings, sand, process water and binder (90% blast-furnace slag; 10% Portland cement). EM experiments were performed using a broadband network analyzer (20 MHz to 1.3 GHz) in the lab and capacitance probes (70 MHz) in the lab and field. Results showed that the EM properties are sensitive to curing time, operating frequency and specimen composition including binder content. The volumetric water content interpreted from dielectric permittivity varied little with curing. Temporal variations in electrical conductivity reflected the different stages of hydration. Laboratory results aided interpretation of field data and showed that a reduction in binder content from 4.5% to 2.2% delays setting of CPB from 0.5 days to over 2 days, which has important implications for mine design.

Modern mines require systems that quickly deliver backfill to support the rock mass surrounding underground openings. Cemented Paste Backfill (CPB) is one such backfilling method, but concerns have been raised about CPB’s liquefaction susceptibility especially when the material has just been placed, and if it is exposed to earthquakes or large mining induced seismic events. Conventional geotechnical earthquake engineering for surface structures is now relatively advanced and well accepted, and so the objective of this thesis is to consider how that framework might be extended to assess the liquefaction potential of CPB. Seismic records were analyzed for earthquakes and for large mining induced events. Important seismological trends were consistent for rockbursts and earthquakes when the signals were recorded at distances as proximate as one kilometre, suggesting that the conventional earthquake engineering approach might plausibly be adapted for such design situations. For production blasts and for more proximate locations to rockbursts, much higher frequencies dominate and therefore new design methods may be required. Monotonic triaxial tests conducted on normally consolidated uncemented mine tailings demonstrated that the material is initially contractive up to a phase transition point, beyond which dilation occurs. Most importantly the material never exhibits unstable strain softening behaviour in compression, and only temporary or limited liquefaction in extension. The addition of 3% binder results in initial sample void ratios that are even higher than their uncemented counterparts, and yet the material friction is slightly enhanced when tested at 4 hours cure. These results suggest that the flow liquefaction phenomenon commonly associate with undrained loose sand fills will not occur with paste backfill. Cyclic triaxial test results analyzed in terms of number of cycles to failure for a given cyclic stress ratio exhibited a trend consistent with previous tests on similar materials. However, the addition of 3% binder and testing at 4 hours cure resulted in an order of magnitude larger number of cycles to failure – a surprising and dramatic increase, suggesting good resistance of the material to cyclic mobility. Future research is recommended to build on these results and develop more robust methods for liquefaction assessment of CPB.

In this study, the possibilities to produce metallic glass as binder phase in hard metal by means of powder metallurgical methods have been investigated. The aim of the study was to do an initial investigation about metallic glass as alternative binder phase to cobalt in hard metal. Production of samples with metallic glass forming alloys and an amorphous powder as binder phase in hard metal by means of quenching and hot pressing have been performed. Moreover, mechanical alloying of metallic glass forming powder to achieve amorphicity has been performed. The samples and powders were analyzed by means of XRD, LOM, STA, SEM and EDS. The results showed that no glass formation of the binder phase was achieved by quenching, hot pressing or mechanical alloying. However, interesting information about glass formation by means of metallurgical methods was obtained. The main conclusion was that production of metallic glass by means of metallurgical methods is complicated due to changes in the binder phase composition throughout the production process as well as requirements of high cooling rates when quenching and high pressures when hot pressing.

Large voids created by underground mining are backfilled to provide regional ground support. This thesis examines using conventional oedometer techniques and electromagnetic (EM) techniques to characterize consolidation and binder hydration in mine backfill so that EM monitoring can be used in the field to provide real-time feedback to operators to optimize the backfilling process. New techniques are given for interpreting the full range of deformation (initial compression, primary and secondary consolidation). Deformation due to initial compression is non-trivial and may have to be accounted for in numerical back-analyses of field case studies. EM parameters are sensitive to binder content, progress of hydration and loss of water caused by consolidation and binder hydration. The integrated interpretation of consolidation and EM behaviours has significant potential impact on real-time monitoring of mine backfill operations, and recommendations are made to advance the technique for this purpose.

Large voids created by underground mining are backfilled to provide regional ground support. This thesis examines using conventional oedometer techniques and electromagnetic (EM) techniques to characterize consolidation and binder hydration in mine backfill so that EM monitoring can be used in the field to provide real-time feedback to operators to optimize the backfilling process. New techniques are given for interpreting the full range of deformation (initial compression, primary and secondary consolidation). Deformation due to initial compression is non-trivial and may have to be accounted for in numerical back-analyses of field case studies. EM parameters are sensitive to binder content, progress of hydration and loss of water caused by consolidation and binder hydration. The integrated interpretation of consolidation and EM behaviours has significant potential impact on real-time monitoring of mine backfill operations, and recommendations are made to advance the technique for this purpose.

[Truncated abstract] Characterising the behaviour of calcareous sediments that possess some degree of bonding between their constituents has attracted worldwide research interest in recent years. Although many recent studies have made significant contributions in delineating the behaviour of these sediments, there is still paucity of information particularly on the cyclic behaviour of cemented calcareous soils. This thesis describes in detail the characteristic features of cemented calcareous soils and proposes methods for characterising their cyclic behaviour. Two different calcareous soils Goodwyn (GW) and Ledge Point (LP) soils representing extreme depositional environments were examined in this study. Artificially cemented sample were created using the CIPS (Calcite Insitu Precipitation Systems) technique, considering its superiority over other most commonly available cementation techniques in replicating the natural pattern of cementation, and the behaviour of natural calcarenite under monotonic loading conditions. The experimental program involved triaxial testing of both uncemented and calcite-cemented calcareous soils under different loading conditions, i.e. isotropic compression tests to high-pressure (16 MPa), monotonic shearing tests, undrained cyclic shearing tests and undrained monotonic post-cyclic shearing tests. Significant emphasis has been placed on the cyclic behaviour of these soils. Internal submersible LDVTs were used for the accurate and continuous measurement of strain down to about 10-5