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Undulatory extinction in quartz is a wide spread feature found in many different rock types. The degree of undulosity exhibited is a function of the processes of rock formation and deformation. As undulosity suggests a level of instability of the quartz, the degree of undulosity has been used, for some time, to indicate the potential reactivity of the quartz in the alkali-silica reaction. The method of routine measurement of the degree of undulosity, on investigation, has been found to be inaccurate. A new method for this routine measurement is proposed, utilising the universal stage assembly fixed to a petrological microscope. Instability of quartz grains can also be gauged by the assessment of grain textures, grain and crystallite sizes. Analysis of 70 quartz-bearing rock types from different parts of UK has been carried out. The results indicate that if all these features are investigated and quantified then it is possible to classify the stability of the quartz, and therefore assess the potential for reaction in the alkali-silica reaction. Three aggregate types, containing quartz with undulose extinction, have been identified as being either reactive or potentially reactive: Dry Rigg Siltstone, Horrocksford (Siliceous) Limestone and the Coedana Granite. Two of these aggregates, the siltstone and the limestone, have been shown to be reactive when used in concrete road and bridge structures. The third, the granite, has been identified as having quartz with a very high degree of undulose extinction, and other deformation features, which indicate this as being potentially reactive. Concrete test prisms have been made with alkali levels of 7.0kg/m3 to investigate if the aggregate type has any affect on the composition of the reaction product, the gel, being produced when stored at 38oC and 100% RH. The three aggregate types do produce gels of different composition, though this is not conclusively attributed to the aggregate type. It is concluded that there may well be a relation between the composition of the gel produced and the type of aggregate reacting, but this may well be overprinted by reactions that have taken place between the time of the expansion measurement ending and the time of chemical analysis by EPMA.

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Models of upper mantle and crustal processes relating to metamorphism can be proposed if the distribution of temperature and pressure during a metamorphic event is known. Knowledge of the distribution of temperature and pressure during the Dalradian metamorphism in the west and south west Scottish Highlands has not materially increased since Elles and Tilley (1930) applied Barrow's (1912) zones to this area. This study was initiated to improve this situation. Rocks from an area 3 miles by 2 miles, east and south east of Spean Bridge, 15 miles east of Tort William, Inverness-shire, were studied to find the conditions of metamorphism, temperature and pressure and the composition and behaviour of the fluid phase attending metamorphism. The rocks are siliceous dolomites, carbonate-bearing pelites (calc-pelites), Ca-rich, but carbonate-free pelites, graphitic pelites and graphitic calc-pelites of the Leven Schists metamorphosed in the garnet zone of the epidote amphibolite facies. Characteristic assemblages are: pelites: quartz-oligoclase-biotite-chlorite-muscovite-garnet-epidote-ilmenite; siliceous dolomites: quartz-oligoclase-phlogopite-chlorite-talc-tremolite-calcite-dolomite-rutile; calc-pelites: quartz-oligoclase-biotite-chlorite or muscovite-epidote-calcite-calcite-dolomite-sphene and/or rutile. The rocks show a considerable variety of assemblages which appear to be in textural equilibrium. The preponderance of low variance assemblages and the occurrence of apparently incompatible assemblages, even on a thin section scale, suggest that the fluid phase composition was buffered by the assemblage. The relationship of fluid pressure to solid pressure and the composition of the fluid phase are discussed and it is concluded that P_fluid = P_total and P_CO₂ + P_H₂O = P_fluid are good approximations except in the graphitic rocks where methane was an important component of the fluid phase. The metamorphic variables that control the assemblages are considered to be temperature, pressure and X_CO₂ (and X_CH₄ in the graphitic rocks). The descriptions and calculations on the assemblages are considered in terms of a model system, K₂O-CaO-MgO-Al₂O₃-SiO₂-CO₂-H₂0, with the phases quartz, anorthite, calcite, dolomite, talc, tremolite, clinochlore, muscovite, phlogopite, clinozoisite and grossularite which are components of minerals found in the assemblages. A thermodynamic background for the calculation of metamorphic conditions is presented. The calculations are only as reliable as the thermodynamic data. The errors on the best calorimetric determinations of enthalpies of minerals become unacceptably large when applied to the enthalpy change of a reaction because the enthalpy of reaction is often an order of magnitude smaller than the enthalpy of individual minerals. The corollary is that precise relative thermodynamic data can be calculated from experimentally reversed reactions. A calculation method is presented and is used to derive themodynamic data for the model system phases and, in addition, forsterite, enstatite, sphene, wollastonite, annite, Fe-chlorite, almandine, Fe-staurolite, Fe-chloritoid and Mg-cordierite. These data and the activities of the model system components in microprobe analysed minerals are used to infer the metamorphic conditions. The % MgCO₃ in calcite in equilibrium with dolomite provides a geothermometer with the experimental calibration of the calcite-dolomite solvus in MgCO₃-CaCO₄ by Goldsmith and Newton (1969). The natural carbonates contain iron, but Fe is shown to have little or no affect on the solvus. About 20 calcites from each of seven calcite-dolomite bearing rocks were probe analysed to apply the calcite-dolomite geothermometer. There is evidence from the area of two metamorphic events, a main event affecting the whole area and a late event affecting only the siliceous dolomites. The calcites from the rocks, apart from the siliceous dolomites show a narrow range of composition, representing a temperature of 546°C at 2 kbars or 530°C at 6 kbars. There is no indication of a temperature gradient across the area. The analysed assemblages are all univariant in the model system; one variable, tempeature, is fixed. so that the others can be calculated. A graphitic assemblage - quartz-oligoclase-biotite-chlorite-clinozoisite-tremolite-calcite-dolomite-graphite - is univariant if the fluid phase contained methane. Applying the calcite temperature, this assemblage formed at about 5.6 kbars with X_CH₄ = 0.30 and X_CO₂ = 0.40.</li> <li>Two calc-pelitic assemblages <ul> <li>quartz-oligoclase-biotite-chlorite-epidote-calcite-dolomite</li> <li>quartz-oligoclase-biotite-muscovite-epidote-calcite-dolomite</li> </ul> give pressures of 4.8 and 5.0 kbars and X_CO₂ = 0.55 and 0.60 respectively.</li> <li>The fine grained parts of the siliceous dolomites appear not to have been affected by the late event. Two different assemblages <ul> <li>quartz-oligoclase-tremolite-talc-dolomite-clinochlore</li> <li>quartz-oligoclase-tremolite-calcite-dolomite-clinochlore</li> </ul> give pressures of 4.5 and 4.7 kbars and X_CO₂ of 0.3 and 0.8 respectively.</li> <li>The carbonate-free pelitic assemblages are compositionally far removed from the model system. Although they are model invariant (if X_CO₂ = 0), reactions that intersect to form the invariant point do not converge in the pressure range of metamorphism. This is interpreted as being due to the failure of the method for calculating activities at this degree of dilution. The conditions of metamorphism for the main metamorphic event from 1, 2 and 3 above are concluded to be about 5 kbars at 535°C with variable fluid phase composition. The siliceous dolomites have been recrystallised along irregular surfaces on which large tremolites are developed. The assemblage in the coarse grained part of the siliceous dolomites is model invariant, quartz-albite-phlogopite-talc-chlorite-tremolite-calcite-dolomite. This represents metamorphic conditions of about 420°C and 1 kbar. The calcites from the siliceous dolomites have a wide spread in %MgCO₃. This is interpreted as re equilibration at a lower temperature than the main event, probably between 400°C and 450°C. Fluid inclusion studies (by Mr F.W. Smith , Durham University) on a semi-conformable quartz vein from within the area defines a pressure temperature band for the formation of the quartz vein. This intersects the band of calcite temperatures and corresponds with the calculated conditions for the siliceous dolomite assemblage. The late metamorphic event, at about 420°C and 1 kbar, is interpreted as a late flushing through of the area by magmatic or metamorphic iLuids along fractures through the pelites and into the more permeable rocks along minor planes of weakness to form the coarse assemblage of the siliceous dolomites and partly re-equilibrate the calcites. The distribution of sphene and rutile in calcite-quartz bearing assemblages cannot be interpreted as equilibrium if the above calculations are crrrect. For sphene to have been stable, the X_CO₂ must have been less than 0.03. It is considered that sphene is metastable in many of the calcite-quartz bearing assemblages, casting some doubt upon the conclusions of Ernst (1971) on the fluid phase composition during the Franciscan and Sanbagawa metamorphism.

With the aim to achieve a better understanding of the time-dependent behaviour of clays, particularly stiff natural clays, a critical review of literature and a program of laboratory testing have been carried out as part of this research work. With emphasis on examining the effects of viscosity and ageing, a series of advanced triaxial and oedometer tests were conducted, which have added significant data to the existing database of results and addressed important "grey areas" highlighted from the literature review. The performed experimental studies included a) An examination of the influence of ageing and global axial strain rate on the vertical elastic shear stiffness of kaolin and reconstituted London Clay in one-dimensional and isotropic compression test combined with bender element testing. b) Characterisation of the influence of strain rate and strain acceleration on the monotonic stress-strain behaviour of reconstituted London Clay from a complex series of triaxial compression and extension tests. c) An examination of the influence of structure, both natural and artificial, on the strain rate dependent behaviour of London Clay and artificially cemented kaolin in triaxial compression tests, in addition to an investigation of the influence of ageing (in this case curing of the cement) on the monotonic behaviour of cement-mixed kaolin. Based on the literature review and findings from the performed experimental studies a framework for the conceptual time-dependent behaviour of natural clays was formulated with the underlying intention to characterise parameters that could eventually be used in a model for natural clays. Finally, on the basis of proposed conceptual behaviour a preliminary numerical study was carried out examining the implementation of general viscous behaviour into the advanced BRICK model of soil behaviour. KEYWORDS: clays fabric/structure of soils laboratory tests time dependence.

Meteorites appear to be the most primitive objects in the solar system and, therefore, contain valuable information on the early history of solar system material. The most abundant meteorites, the chondrites, are characterised by the presence of small spherical silicate inclusions, chondrules. Although the chemical, mineralogical and petrological properties of chondrules have been investigated their purely physical properties have received little attention. The present thesis therefore examined the size, shape and orientation of long axes of chondrules and tested the fit of chondrule mass distribution to known statistical functions in order to obtain constraints on the origin of chondrules and the accumulation and early history of meteorites. The size range of chondrule diameters was found to be rather limited from a pronounced lower limit cut-off around 0.2mm up to a few millimeters. A preponderance of particles of smaller diameter (~0.3 - 0.7mm) was observed. Although there appeared to be no marked difference in chondrule size distributions in the ordinary chondrites, those in the carbonaceous chondrites are more restricted with a greater preponderance of smaller particles. Departures from sphericity of chondrules were found to be small and random. Chondrule mass-frequency distributions could be fitted to the Weibull statistical function (except for Nikolskoe) but were found not to obey Rosin's law suggesting, by analogy, that chondrules were not produced by crushing phenomena. Most chondrites were found to exhibit some degree of preferential orientation of chondrule long axes which was less marked in relatively friable meteorites and appeared unrelated to degree of metamorphism. It was concluded that the observations suggest that chondrules are most probably secondary objects formed by a high-energy event acting on material with a restricted mass range. Accumulation of meteoritic material was a gentle process with the petrofabric most likely being imposed during this period.

Although the problem of the expansion of pyritic mudrock has only come to light in the last 10 years, the possibility of the problem occurring is known to engineers across the world. The mechanism behind the reaction process, the oxidation of pyrite and secondary precipitation of gypsum, is reasonably well understood and is highlighted in a series of case histories. This piece of work collated this information and brought it into a single document such that the reaction information and the case histories can be referred to and used to prevent or better understand future cases. Irish Standard IS 398-1 was used to analyse a series of Irish properties in order to determine whether it is possible to correlate between the level of damage seen in a property and the chemical and geotechnical information obtained from the fill. Although initial results are unclear due to the influence of factors not accounted for in the data available and the variation of the fill material, further work on this method is encouraged as data refinement and numerical/statistical modelling are likely to produce clearer results. This thesis also considers the current cases in Ireland, and the experimental work that has been carried out, in order to present a) a better understanding of the Irish situation, and b) to show the influence upon the development of laboratory tests to study the factors that influence the reaction process. This information was used to guide the development of both laboratory work and field monitoring systems, the latter included placement of a monitoring system below a domestic floor slab. Although data available from the system was incomplete, initial analysis shows that the temperature in the fill is influenced both by changes in the external temperature and in the temperature of the room above the slab. In the laboratory, tests were designed to build upon previous work, confirming the influence of the density of the material upon the reaction rate and amount, and also showing the influence of the grading of the material on the reaction process. This indicated that the process of using well graded fill material gives a long-lasting reaction process wherein the fine material reacts initially whereas the coarse material reacts slower but for longer as the air and water take time to reach the pyrite in the centre of the larger rock particles.

Primitive chondrite components in six carbonaceous chondrites, Bencubbin, HaH 237, Gujba, Isheyevo, Acfer 209 and Acfer 094 were studied to examine the complex thermal histories of individual particles. Significant information about the origin and evolution of the solar nebula is contained within primitive chondrite components including FeNi metals, sulphides, matrix material and calcium aluminium inclusions, allowing conclusions to be drawn about the conditions which prevailed in the early nebula. This thesis describes the analysis of meteoritic metal and other components in carbonaceous chondrites using a suite of complementary techniques including secondary electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), secondary ion mass spectrometry (nanoSIMS), grain-size frequency distribution (GSFD) and computed tomography. Metal is chosen as the primary comparative component as it is a common feature in carbonaceous chondrites and is an indication of the extent to which a sample has been exposed to thermal, metamorphic and alteration processes. EBSD results reveal a variation between chondrule-associated metal and matrix metal in CR chondrite Acfer 209 and the ungrouped chondrite Acfer 094 indicating a difference in formation and subsequent processing. TEM results demonstrated that evidence for aqueous alteration occurs on a sub-μm scale on the rims of FeNi metal grains in Acfer 094. FeNi metallic rims displayed regions of pitting corrosion and an enrichment in O and Ni accompanied by depletion in Fe. These features indicate interaction with an aqueous fluid. Grain-size frequency distribution analyses revealed a strong and common mode in the metal grain aspect ratios of three samples from the CB group of chondrites indicating a common deformational event. The presence of adjacent primitive components with varying chemical and crystallographic textures reveals that these samples were subject to a complex thermal history. Fine-grained matrix material in HaH 237 is heavily hydrated and shows no complementarity to chondrules which escaped aqueous alteration consistent with the X-wind model. In contrast, matrix material does show compositional complementarity to chondrules in Acfer 094 and Acfer 209. This suggests material for both components formed in the same region of a nebula conforming to the shock model where material formed on the disk.

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