Autogenous laser beam welds were made in sheets of the aluminium alloys 8090, 8009 and 6061. The Al-Li based alloy 8090 was subjected to both continuous wave CO2 and pulsed Nd:YAG thermal cycles with average powers of 1.5-3.8 kW and 0.8- 0.9 kW respectively. The two techniques were compared for their influence on the 8090 solidified weld pool shape, the fusion zone microstructure and microhardness, the HAZ and the susceptibility of the fusion zone to post-weld heat treatment. It was found that CO2 keyhole welding is preferable to Nd:YAG welding, under the welding conditions investigated, as essential elements such as Li and Mg were lost by evaporation during Nd:YAG processing. Microscopy of the 8090 CO2 weld fusion zone revealed that the solidification mode was sensitive both to the temperature gradient and growth rate during solidification, with a transformation from cellular to equiaxed dendritic growth occurring from the weld pool edge to the weld centre. The secondary dendrite arm spacing was found to be 2-5µm and the metastable phase δ (Al3Li) was present after welding with a very fine homogeneous distribution of -5nm diameter spheres. Porosity was identified as a major welding defect and was attributed to two distinct formation mechanisms. Firstly, the release of hydrogen gas during welding caused spherical gas bubbles throughout the weld pool. Secondly, the delicate balance of forces within the keyhole resulted in larger irregular shaped pores at the weld centre-line towards the weld root. This second type of pore was virtually absent in full penetration welds. The influence of heating rate to the solution treatment temperature on 8090 CO2 weld metal was assessed and the weld metal grain size was found to be most uniformly small after a heating rate of 1 K/min. A TEM investigation confirmed that the grain boundary pinning dispersoid β(Al3Zr) was responsible for inhibiting grain growth. However, the microhardness and notch-tensile strength of the CO2 weld metal did not depend on the weld metal grain size. Instead, it was suggested that the residual cast structure was responsible for determining the mode of failure and fracture strength. Microstructural studies of CO2 laser welds in RSIPM 8009 and wrought 6061 confirmed the cooling rate of 102-103 K/s predicted for CO2 welds in 8090. However, the 8009 CO2 weld metal did not solidify by epitaxial growth from the fusion boundary, which was the case for CO2 welds in 8090 and 6061. Instead, solidification in 8009 weld pools occurred via many isolated events on primary intermetallic particles. The intermetallic particles had the stoichiometry Al4.5(Fe,V,Si) with the AI.mFe tetragonal lattice parameters. It was qualitatively shown that the 8009 weld microhardness had an inverse relationship with the volume fraction of intermetallic particles. Chemical analysis of the 6061 weld metal confirmed that even when aluminium is alloyed with volatile elements such as Mg it is mostly retained within the weld pool during CO2 keyhole laser welding. It was found that a much higher power was required to obtain a deep penetration weld in 6061 than in either of the other alloys.

Surface mine planning involves the results of algorithmic numerical calculations being used by engineers to make informed decisions relating to the design. The Department of Mining Engineering at the Unversity of Nottingham has in the past been involved in developing modular algorithmic packages. The emphasis of the computer research has now altered. Smaller specialised systems are now being developed to cover individual aspects of the design process. Artificial intelligence techniques are being introduced into the mining environment to solve the planning problems often associated with the large amounts of uncertain information needed by the engineer. This thesis is concerned with the development of MINDER, a decision support system capable of assisting the mine planner in the complex task of optimum surface mining equipment selection. An expert system shell has been used to create a series of individual application modules, each containing a multi-level knowledge base structure. An information handling system has been developed which is capable of storing consultation information and transfering it between knowledge bases and between application modules. Once an effective method of information handling had been achieved the flow of control between the system knowledge bases was rapid and followed complex inferencing routes. Most of the commercially available packages mathematically model a deposit, calculate volumes and simulate operations. One of the aims of the MINDER system was to integrate with other software, for example MINDER is capable of reading volumetric and material information from Surpac mine planning software. Geological data and manufacturer’s equipment specifications are stored in DbaseIV databases. The expert system is capable of writing macros based on the consultation and performing complex relation operations involved in the elimination and ranking of equipment. In a similar manner macros are written to control the simulation package GPSS which used to simulate operations using the selected equipment. A range of ‘in-house’ Pascal software is used for numerical calculations and matrix manipulation, an example of this is the fuzzy logic software used to handle uncertain information. Another aspect of the project is an investigation into the use of machine learning techniques in the field of equipment selection. Knowledge induction software has been used to induce new rules and check those produced in the MINDER system. Various experiments have been carried out using neural network software to produce equipment selection models. Training data taken from the mining industry was used on both these systems and the results were tested against MINDER consultation results.

Plain-fatigue and fretting-fatigue tests have been carried out on the two peak-aged, high-strength aluminium alloys, 7010 and 8090, in the unpeened and shot peened conditions. Shot peening produced a highly deformed surface containing many deep dimples and folds from which fatigue cracks rapidly initiated. Although initiation was early, propagation through the peened surface layers was retarded by the residual compressive stresses introduced by the peening treatment; this retardation being greatest at a depth corresponding to that of the peak residual compressive stress. Shot peening improved the plain-fatigue properties of the 7010 alloy at high applied stresses and this improvement decreased as the applied stress was reduced. A reversed trend was observed in the 8090 alloy with shot peening being beneficial to the fatigue properties at low applied stresses and detrimental at high applied stresses. The poor resistance of the 7010 alloy to fretting-fatigue was eliminated by shot peening and this was again attributed to the residual compressive stress induced by the peening treatment. Since the 8090 alloy in the unpeened condition is relatively insensitive to the effects of fretting, shot peening resulted in only a minor improvement in the fretting-fatigue behaviour of this alloy.

In recent years the drivage advance rates achieved within the UK coal industry have increased. In the 1980's average drivage rates were 35m per week compared to the 100/150m per week possible today. These extended rates of advance have resulted in an increase in the potential methane, dust and heat generation within the vicinity of the drivage face. In order to effectively disperse this additional pollutant load a controlled increase in air quantity is required. Although advance rates have changed, current auxiliary ventilation practice has not. UK mining law requires that the fresh air must be delivered to within 5m of the face. This has lead to the wide spread adoption of the use of overlap auxiliary systems within mechanised drivages, since a pure forcing system set at this distance from the face would lead to excessive airborne dust. UK mining law does not at present consider on-board mounted exhaust scrubber fans to constitute an effective overlap fan within mechanised drivages. Consequently an additional overlap exhaust fan is required to be installed within such drivages. In an attempt to determine whether working conditions could be safely and economically improved within mechanised rapid development drivages utilising an on-board mounted exhaust fan, a series of preliminary full scale gallery trials were conducted. A summary of the principal findings of these trials is presented together with an outline of a series of representative CFD simulations. This thesis examines the accuracy of CFD simulations for auxiliary ventilated headings. This is achieved by utilising Laser Doppler Anenometry (LDA) in a scale model representative of an underground heading and a detailed underground measurement programme conducted in production headings. These measured airflow values are then compared with representative CFD simulations and conclusions

This research aimed to establish a physical relationship between applied stress and permeabilities of different coals. Seven different coals, ranging from medium volatile to high volatile bituminous, were tested for stress-permeability relationship under simulated subsurface stress conditions. Prior to the experimental investigations, the stress conditions around a working longwall face were considered in order to achieve an accurate simulation of the stresses experienced underground. Laboratory stress-permeability experiments were carried out by passing nitrogen gas through a triaxially stressed cylindrical coal specimen. A slightly modified conventional triaxial testing apparatus was used for this purpose. The stress conditions employed simulated the stresses created in the front abutment zone, the crushing zone, the stress relief zone and the recompaction zone of a working longwall face. A number of specimens of the seven different coals were tested under such stress conditions and stress-permeability curves were obtained for each specimen. The effect of moisture and the direction of gas flow in relation to the direction of bedding planes and major fracture lines were also considered in laboratory investigations. A relationship between the stress-permeability behaviour and the rank of coals used was established. Combining the general pattern of stress-permeability behaviour obtained in this research together with the stress conditions created around a working longwall face a model was produced which presents the stress-permeability profiles of coal seams in the vicinity of the workings. From these profiles it was possible to suggest the flow patterns of gas around working longwall faces.

This research describes an investigation into the application of a statistical method for the prediction of methane concentration in longwall coal districts. An important and necessary part of the research was the acquiring of representative mine environmental and coal production data and a number of shortcomings were identified in this area. The monitored data was used to build univariate time series models of general air body methane concentration, air velocity, barometric pressure, coal production and methane drainage variables of varying timescales according to the Box-Jenkins method of time series analysis. The univariate models were used to identify causal relationships between methane concentration and its explanatory variables. Coal production was found to be the dominant variable in the determination of the quantity of methane emitted and where appropriate, multivariate time series models were built in which expressions for methane concentration in terms of coal production were obtained. Forecasts of methane concentration values were generated from both univariate and multivariate models and a comparison was made of their forecasting capabilities. Finally, suggestions were made as to the potential use of time series models for application to mining process control.

Microwave assisted leaching has been investigated in an attempt to improve both the yield of extracted metal and reduce processing time. This is especially pertinent in view of the increased demands for metal and more environmentally friendly processes. This work reports a fundamental study on the influence of microwave energy on the dissolution of sulphide minerals. Chalcopyrite and sphalerite were chosen as model materials due to their economic importance and the diversity of their heating behaviour in a microwave field (chalcopyrite being an excellent microwave heater and sphalerite being an extremely poor microwave receptor). Chalcopyrite leaching has been carried out in ferric sulphate and ferric chloride under both microwave and conventional conditions. Conventionally, it was found that chalcopyrite dissolution in ferric sulphate seems to be limited by surface reaction control. More importantly, it has been shown that specific fracture planes on chalcopyrite particle surfaces experience selective leaching, which was revealed by SEM and ToF-SIMS surface analysis. The preferential attack on particular planes is speculated to be linked to different chemistry of some cleavage planes within the chalcopyrite crystal. In the ferric chloride system, however, it was found that cupric chloride, a reaction product of chalcopyrite with ferric sulphate, may play an important role in the dissolution process. Leaching of both chalcopyrite and sphalerite in ferric sulphate under microwave conditions has shown enhanced recoveries of metal values compared to that produced conventionally. It has been demonstrated that the enhanced copper recovery from chalcopyrite during microwave treatment is as a result of the selective heating of the mineral particles over the solution which was found to be highly lossy. In addition, it is suggested that high loss leaching solutions will develop a superheated layer close to the periphery of the reaction vessel (due to the small penetration depth) which creates localised heating compared to the bulk solution temperature. The enhanced recovery of zinc from sphalerite seems to occur as a result of only the presence of the superheated layer. If leaching takes place within this layer, an apparent rate increase will be noted with respect to the measured bulk temperature. The hypotheses of selective heating (for chalcopyrite) and the effect of penetration depth (for chalcopyrite and sphalerite) were supported by the negligible difference between the activation energy values under microwave and conventional conditions for both chalcopyrite and sphalerite. Furthermore, the measurements of dielectric properties of the leaching solutions have shown that such solutions are highly lossy and characterised by a penetration depth of an order of about 3 mm. Finally, numerical electromagnetic simulations showed that chalcopyrite particles could be heated selectively when micro-waved within highly lossy leaching solutions due to their high conductivity. It is concluded that the dielectric properties of both the solid and liquid phases, the dimensions of the reactor and the position of solid particles within the reactor determine the leaching outcome. More importantly, it is likely that the enhanced recoveries observed are not likely to be as a result of a so called "non-thermal microwave effect" but rather as a result of thermal effects.

Despite the large number of modifications proposed to the standard Cam-clay models over the last three decades, the critical state concept has been much less successful for modelling sand behaviour. This thesis is concerned with understanding the stress-strain and strength characteristics of Portaway sand, a quartz sand, and the validity of several recently developed critical state models formulated in terms of the state parameter concept. The laboratory investigation consisted of the evaluation and modification of two triaxial systems and 83 triaxial tests performed under monotonic and cyclic loading conditions. Emphasis has been placed on assessing the applicability of critical state theory and state parameter concept to sands. Portaway sand was chosen in this research work because it is a typical granular material for which the deformation behaviour can be obtained and used to verify the newly developed constitutive models. The critical state model concerned is known as CASM developed by Yu (1995, 1998). CASM is a relatively simple model because it only requires seven model constants, five of which are the same as those used in the modified Cam-clay model. Three extensions of CASM referred to as CASM-b, CASM-d and CASM-c were developed recently based on the combined hardening concept and the bounding surface plasticity theory. These enable the smooth transition of stiffness, phase transformation and cyclic behaviour to be simulated. For the first time, a simple procedure for determining all the model parameters from triaxial results has been established. The validities of the theoretical assumptions introduced in the new models are critically assessed in light of results obtained from both element testing and numerical modelling. In general, the overall stress-strain behaviour of Portaway sand observed in triaxial tests under various stress paths is well captured by the models.

The drilling industry, along with many others, is becoming increasingly competitive, demanding greater efforts to improve safety and reduce costs. For this reason, companies are progressively looking towards computerised automation to enhance performance. Unlike most industries however, the drilling industry has been slow to take advantage of the advances in computer and automation technology. Only recently have automatic operations such as tubular handling been placed under computer control. These activities relate to peripheral mechanical handling problems which are relatively easy to solve. The concept of an automatic intelligent drill, capable of making its own or assisted decisions about drilling parameters such as weight on bit or rotational speed, may seem remote and far into the future. Research in drilling automation, at the University of Nottingham, has the ultimate objective of achieving computerized drill control through the the application of an intelligent knowledge induction system. At the University, a laboratory rig has been developed with such a system installed. Decisions for optimal performance are based on either maximum penetration or minimum cost drilling. The system has a self-learning capability, allowing a progressive improvement in performance. The prototype system is currently undergoing trials, using real data collected while the laboratory rig is drilling and artificial data. The results are very encouraging and demonstrate the feasibility and advantages of optimised drill performance. This thesis describes the design and development of this drill optimisation scheme produced by the author. Both the theory behind the optimisation system, and the results of the initial phase of Laboratory testing are included.

This research describes an application of numerical methods for the prediction of strata methane flow into mine workings around a longwall coal face employing methane drainage. This method of methane prediction was developed by solving the time-dependent gas flow equation using the finite element analysis. Having obtained the gas pressure distribution throughout the finite element mesh, a mass flow equation was derived to calculate methane flow rate for a given mining boundary. A computer program for the prediction of methane flow was then developed by devising appropriate modifications and additions to a finite element package originally written for heat flow by PAFEC limited. Stress analysis was also carried out in order to provide an understanding of stress fields around a longwall face to evaluate the induced permeabilities under these stress fields. Three main routines of the original package required modifications to accommodate the solution of a different equation. These were element routines, solution routines and flux calculation routines. These routines, after modification, were used to simulate advance and retreat longwall mining, with and without drainage. Several different sensitivity tests were carried out by changing parameters such as borehole pressure, length, and spacing in order to aid the planning of methane drainage systems for longwall mining.