Borehole instabilities can be encountered at any stage in the life of a well and they are the main cause of drilling difficulties, resulting in substantial expenditures, expensive loss of time, sometimes even in the loss of part of or even whole boreholes. The main aim of this research is to use new method and theory in geomechanics to conduct the stability analysis of wellbore. The cavity contraction theory is used to get the new elastic-perfectly plastic solutions for vertical borehole with anisotropic stress field. The solutions for Mohr-Coulomb and Hoek-Brown criteria are derived in this paper. A new alternative criterion, which is to limit the radius of plastic zone around borehole, to predict the wellbore instability was also recommended. The finite element code ABAQUS is applied to analyse the mechanical behaviour of wells with different inclinations and different azimuths. A Generalized Plane Strain Model is used in the calculation. The failure wellbore pressure, borehole closure, plastic zone distribution of different direction wells are given in this paper. In order to accurately predict the wellbore behaviour in soft and porous rocks, a suitable and advanced constitutive model of rocks is the key issue of the borehole instability research. A new model, called CASM (Clay And Sand Model) which is based on critical state theory and formulated in terms of the state parameter concept is applied in this research. The non-coaxiality theory is incorporated into CASM to analyse the wellbore stability. Compared with coaxial model, non-coaxial model gives more pessimistic results. However, it was found that the influence of non-coaxiality on wellbore stability depended on initial conditions of wellbore.

Haulage Costs account for a considerable portion of a surface mine's operational budget. It is therefore vital that, for a particular pit configuration, the optimum utilisation of the available truck fleet is adopted during the mine's life. Also, if the optimisation methods are established beforehand, it is possible to determine exactly how many trucks will be required. Both decisions can be made at the planning stage by the application of linear programming and discrete simulation to computer models of the haulage network. The project presented herein investigates the practicality of developing a general-purpose mine transportation selection and scheduling system within the context of a Computer Aided Design (CAD) environment. Compatibility with a purpose-built, interactive graphics package is shown to enable rapid, semiautomatic generation of model networks and the planning engineer is assisted further by the robust and friendly user-interface which has also been developed. Unlike a number of existing packages, which either make use of commercially available software on a stand-alone basis or were specifically designed for the analysis of a particular operation, this system is completely integrated with a central database which makes it applicable to any mine. The enhanced ability to produce valid mathematical solutions and their associated network models using the above systems, allows a large number of configurations and dispatching policies to be compared in a relatively short space of time. However, attention is also paid to the degree of correspondence with what can be achieved in reality since this will also effect the selection decision. All the modules mentioned form part of a much larger planning system currently being developed at The University of Nottingham, Department of Mining Engineering, known as NUmine.

The work carried out in this thesis outlines some of the problems associated with abrasive wear in machines and other mechanical equipment used to excavate or process natural rock material. It has been stated that if the problems associated with abrasion are to be better understood, then a sound knowledge of the abrasive potential of rocks is essential. A number of common wear mechanisms are described together with existing hardness and abrasive tests. The author has investigated rock hardness and abrasiveness by the use of existing methods and subsequently, developed new correlated with the well tests which can be established methods of determining physical and mechanical properties of rock. A project on hard rock drilling has been conducted to determine the rate of wear on expensive diamond impregnated coring drill bits. A detailed investigation which involved the design and manufacture of special measuring equipment to accurately measure and record changes in the profile shape of the bit during its life span. This has permitted a study of the wear characteristics related to the various drilling parameters employed. A collaborative project was carried out with DeBeers, UK, to attempt to discover methods of predicting the rate of specific wear on diamond impregnated saw blades and the cutting forces required with the sawing of hard stone materials. This project has led to a new statistical approach to the analysis of the acquired test data for this purpose. A number of case histories have been discussed and recommendations made. As a result of these investigations together with the work covered in this thesis, the author has developed two new abrasive tests. These tests can be used to test materials such as unconsolidated rocks which otherwise, could not be satisfactorily tested by the established tests already in existence. The new tests have been tried and proved by correlating the test data by combining multiple regression analysis with the results obtained from physical and petrological rock property tests with actual rock cutting data. Conclusions have been drawn and recommendations for future work suggested.

This document constitutes a brief discussion of the total concept of mining limestone, particularly for lime and cement manufacture. Actual case studies in which the writer has participated have been used to demonstrate the methods used by the various operators and their attitude to matters such as the environment has been described. The document has been written to be presented as suitable material for the Degree of Doctor of Philosophy, however, on reading several cotemporary theses which deal solely with the matter concerning the degree, the writer has chosen to produce a document that compiles material from a multitude of sources, including the writers own experience which he thinks may be of interest to mining students. The part of this document that complies with the requirement to "advance science" is in the use of explosives and the principles of rock breakage, this is the main area of the writers expertise and is to be found, in Chapters ten and eleven. The method of blasting and the reasoning for its evident success, challenges some, and agrees with other, mathematical theorem that have been presented previously. Most mathematical theorem use either perfect models, or require so many variables that the accuracy of the maths becomes doubtful, because of this, their usefulness to the mining engineer is limited. Chapter eleven explains how explosives work in surface mining and identifies enhanced effects. The writer believes that these enhanced effects are the result of coincidences in the pulses of the shock waves. The writer first noticed the effects of a shock wave on rock when designing huge blasts for strip mining of coal in Zambia, where the rock had to be totally shattered but remain in place, further experiments in the Falkland Islands with spacing and timing, finally led to application in African limestone quarries. The blasting described at Chilanga has been designed to first shatter the rock then produce further breakage in the enhanced heaving process, in addition, the imperfect rock formation provides a perfect example of using explosives to blend the various grades of material. Many photographs are included of the results of blasting and as the practice is still current, the readers are able to visit Zambia to examine the effects for themselves.

The factors which influence the performance characteristics of diamond impregnated core bits and roller cone bits are examined, and actual field drilling data are analysed to determine these factors. Methods for selecting the appropriate bit type for optimised drilling are also highlighted. The importance of core drilling to the exploration and exploitation of the earth's natural resources and to the integrity of engineering structures is highlighted. An investigation of the slim hole continuous core drilling system and its application in the oil and gas exploration is analysed. The highly successful integration of oilfield, mining and geotechnical exploration technologies in a special investigation programme includes several elements which are important in the application of slim hole methods for oil and gas exploration are analysed. Many of the technical issues associated with a slim hole approach have been addressed in the development and application of the drilling, and coring equipment and systems. The project has given an opportunity to evaluate the advantages and disadvantages, merits and limitations for applying different drilling and associated technologies for deep hole construction to safety.

Microwave energy has previously been shown to have a major influence on the comminution behaviour of minerals and ores. Significant reductions in strength have been observed for microwave-treated ores. Other workers have reported increases in liberation after treatment. However, the majority of the work has been carried out at energy inputs too high for economic implementation. Whilst it was thought that the weakening and enhanced liberation was due to differential expansion of the heated constituent phases resulting in increased predominance of inter-granular fracture, the exact mechanisms have been poorly understood. Due to difficulties in measuring events inside a microwave cavity and inside the material being irradiated, it was suggested that numerical modelling could be used to simulate a simplified system in order to determine the underlying mechanisms. The model was used to examine the development of stresses as heat was applied to certain mineral phases. No heat was applied directly to the matrix component of the simulated ore. Given sufficient energy input, the stresses would exceed the strength of the material. It was found that the shear stresses in particular were likely to be highest at the edges of the grain boundaries of 2-D circular heated particles inside an unheated (microwave-transparent) matrix. This explained the increased occurrence of inter-granular fracture which has led to observations of enhanced liberation. It was also discovered that weakening is facilitated at very high microwave power densities, due to the increased magnitude of expansion and subsequent forces generated. The overall energy balance can be made favourable by using microwave exposure times of less than 0.1 seconds. Shorter exposure times result in less time for conduction to occur from the heated phase into the unheated phase, and temperature gradients are maximised leading to elevated shear stresses and increased likelihood of fracture.

This thesis applies Smoluchowski's coagulation-fragmentation equations to model the mechanical alloying process. Mechanisms operating during the milling process are reviewed. In the first instance, models are developed that predict the size distribution of a single milled powder while ignoring mixing phenomena. A methodology is developed that allows experimentally measured sieve-fractions to be converted into volumetric cluster size distributions. Model parameters describing the rate of aggregation and fragmentation are obtained by fitting the model's predicted average particle size data over time to that measured in experiments. Different size-dependent aggregation and fragmentation rates are tested in many milling scenarios and the most realistic size-dependence of rates is found. In the second part of the thesis, the best size-dependent rates are generalised and used with a two-component version of \Smol's system of equations. This model also includes binary mixing phenomena by considering clusters that have two types of component. The two-component models are applied to experimental situations using the methods developed for one-component models. Comparing these multi-component models to experimental measurements verifies the modelling method and gives reasonable agreement. An improved fragmentation rate is suggested to enhance the model's accuracy in the prediction of mixing rates.

This thesis aims to develop a rock mass classification system for UK Coal Measure strata such that the output from the classification system may provide a means by which the strength and stiffness properties of Coal Measure strata encountered within UK coal mines may be predicted. The development of the Coal Mine Classification system is described within this thesis. A structured methodology utilising a database of information obtained from 118 different rock mass classifications, together with consideration of the typical mechanisms of strata deformation within coal mines, was employed to determine the parameters of the Coal Measure strata that have the greatest influence on the engineering properties of the strata. These identified parameters have formed the basis of the Coal Mine Classification system. By comparison to a series of conceptual models of strata deformation that occur within the roof ,floor, ribs of roadways and within the region of the coal face, relative importance weightings and rating scales for the identified classification parameters have been proposed. The anisotropic nature of the UK Coal Measures is characterised within the Coal Mine Classification by the calculation of separate ratings for directions parallel to and perpendicular to bedding. An appraisal of the optimum method of using the classification ratings, determined by the Coal Mine Classification, to predict the strength properties of individual strata units was undertaken. Rock mass failure criteria that utilise outputs from existing rock mass classification systems to determine the rock mass strength, have been reviewed. Utilising published triaxial data the rock mass failure criterion that best predicts the failure characteristics of UK Coal Measure strata was identified. From this study the Hoek-Brown rock mass failure criterion was identified as the optimum existing criterion for predicting the intact strength and rock mass strength of Coal Measure strata. However this criterion was still found not to produce a close fit in many cases to the intact failure strength of the strata. A modified Coal Measure Failure criterion has been developed, which for a wide range of Coal Measure rock types was found to produce a better prediction of the intact strength of Coal Measure strata than any of the existing rock mass failure criteria. To determine the efficacy of the Coal Mine Classification system as a means of predicting the strength and stiffness properties of the rock mass the Coal Mine Classification was applied to the strata at case study localities within rock bolted roadways within three UK mine sites. Numerical models of the case study localities were developed using the FLAC finite difference code utilising a ubiquitous jointed elastic-perfectly plastic material model to simulate strata behaviour. The output from the modelling included predicted roof and rib side displacements, and these displacements were compared to the actual monitoring data for the case study localities. The results of the numerical modelling indicate that the predictions produced by the numerical models reflected the pattern and scale of deformations actually measured in-situ within the coal mine roadways, thus indicating that the Coal Mine Classification system provides a means of predictively determining the engineering properties of the in-situ Coal Measure strata. The modelling also indicated that time delays related to the installation of the roof extensometers may under predict that actual roof deformation that occurs within the roadway roof.

The thesis is a study of the stability, closure behaviour and rock fracture development associated with mine tunnels with particular reference to Coal Measures conditions. A detailed survey has been carried out of relevant theories and mathematical concepts which relate to tunnel stability and the effects of in situ stresses. Of special importance has been identifying appropriate mathematical theories which relate to the field of scholarship undertaken. The literature survey has found useful application especially in giving guidance on those areas needing further investigation. The author discusses mathematical theories in relation to the research undertaken. The major area of investigation has been the effect of different in situ stress fields on various aspects of tunnel design and geometrical configuration. Attention has focussed on available research methods which allow ease of investigation of the parameters governing mine tunnel stability. After careful consideration, the author selected physical modelling using small scale sand plaster models of different mine tunnel and geological conditions. Much research effort has been directed at establishing the properties of such physical modelling materials, mathematical scaling aspects and the type of test rig for carrying out the investigations. Time was spent on establishing the accuracy and suitability of the research method employed. A range of experiments were carried out whereby the horizontal and vertical components of the in situ stress field were varied. The tests were repeated using the common range of mine tunnel profiles which exist in UK coal mines, namely arch, circular, square and rectangular. The research enabled the fracture pattern to be observed in association with the different tunnel profiles tested under the various stress field conditions employed. Closure of the model tunnels was observed in relation to the increasing stress field. Discussion has focussed on how various combinations of horizontal to vertical components of in situ stress influence mine tunnel stability. The results are discussed in relation to the choice of support type. In particular, the merits of standing support types such as square sets, steel arches and concrete linings are discussed in relation to the results of the research. The thesis draws attention to the practical application of the research method to investigate various mining situations as encountered in UK coalfields and in the Datong coalfield in North China, of which the author has particular experiences regarding rock mechanics and mine tunnel stability.

Structural and kinetic aspects of precipitation in the systems Mg-Th and Mg-Nd , with various ternary additions, have been studied, using electron microscopy and electrical resistivity techniques. The sequence of precipitation in the Mg-Th alloy is solid solution → β" → β. Small additions of manganese and silver have little effect on the precipitation process but additions of zirconium and zinc alter the process significantly. The β” reaction is completely suppressed by an addition of 0.3% zinc and a phase not present in the binary system, β’ Mg2Th, is formed as two polymorphs in the zirconium containing alloy. The sequence of precipitation in the Mg-Nd system is completely changed by the zinc addition. Alloys containing Mg 2.8% Nd 1.3% Zn have the following precipitation sequence Solid solution → low temperature reaction → plates γ”││ (0001) → rods on γ (0001) in <1120> & <1010> The low temperature reaction has not been elucidated but it occurs with an activation energy approximating to that of vacancy migration in magnesium, and may possibly be associated with short range order. The structures of these various alloys have been correlated with their creep and mechanical properties. In particular, the creep properties of the Mg-Nd-Zn alloy have been shown to be superior to those of the binary Mg-Nd alloy and the improvement has been attributed to the γ" phase restricting dislocation motion on the {1011} planes.