[Truncated abstract] This thesis describes the development of synthetic rock samples, representative of core samples from hydrocarbon reservoirs. The basic process consists of screening and sorting silica particles into discrete grain sizes, and then binding them together using a proprietary process known as CIPS, (Calcite In-situ Precipitation System). In the bonding process, the porosity of the system is substantially preserved, and the technique allows the manufacture of synthetic core samples with a tailor-made permeability. The produced samples were extensively characterised using a variety of analytic techniques to determine their porosity, permeability and pore size distribution. These analyses were a necessary pre-cursor to a major part of this thesis: the characterisation of the pore space by nuclear magnetic resonance (NMR) techniques. The synthetic core samples, covering a 7 times factor in grain sizes were examined using NMR, and this data formed the comparative basis for the NMR studies that followed. Two fundamental NMR questions were posed and answered in this thesis: 1. What is the effect of paramagnetic ions in the rock matrix on the NMR response? In pursuit of this question the CIPS process was extended to include co-precipitation of paramagnetic ions. A key feature is that the ions were deposited in predictable amounts at known sites (on the wall of the pore space). ... The NMR response in these double cores was then measured and examined to provide an answer to the question posed at the beginning of this paragraph. The significance of this work is that the physically distinct cores are a cylindrical analogue of adjoining sedimentary strata. By answering the question posed above, the thesis gives an indication of the vertical porosity resolution ultimately possible in an NMR logging tool. At present this ranges from 9” to 24” in the most favourable circumstances. This work suggests that the NMR signal carries porosity information at a much higher resolution, and that advanced numerical analysis of the NMR signature could realise the potential of greater stratigraphic resolution in NMR logging In addition to the research outlined above, the application of the CIPS technique to produce analogues of reservoir rocks, pioneered in this thesis, has stimulated similar research to be undertaken at other institutions, including the fabrication of synthetic reservoir cores containing clay particles (at CSIRO - the Commonwealth Scientific and Industrial Research Organisation) and a large scale application, formation of meter size blocks of CIPS bonded material, with separate strata, for laboratory studies of seismic waves (at Curtin University)

Η παρούσα διατριβή διερευνά τη μηχανική συμπεριφορά των γεωλογικών σχηματισμών που αναφέρονται ως σκληρά εδάφη-μαλακοί βράχοι και αποτελούν μεταβατική ενότητα υλικών με χαρακτηριστικά αντοχών που τα κατατάσσουν ενδιάμεσα των εδαφικών και των βραχωδών υλικών. Εξετάζει δε τις εμφανίσεις τους σε περιοχές της Πελοποννήσου και ειδικότερα στους Νομούς Κορινθίας, Αχαΐας, Ηλείας και Λακωνίας. Η συγκέντρωση της Διεθνούς και της Ελληνικής βιβλιογραφίας πάνω στο θέμα αυτό αποτέλεσε την αρχική καταγραφή των ιδιοτήτων των σχηματισμών αυτών, όπως έχουν αναγνωριστεί από προηγούμενες έρευνες. Η παρούσα έρευνα διευρύνει τη διερεύνηση των υλικών αυτών στον Ελληνικό χώρο με την εξέταση των μηχανικών παραμέτρων ακολουθώντας τη μεθοδολογία της Βραχομηχανικής. Για την επίτευξη του παραπάνω στόχου αυτού έγινε κατ' αρχήν μελέτη και τροποποίηση των μεθόδων διερεύνησης με σκοπό την προσαρμογή των σχετικών διαδικασιών στην ιδιαίτερη φύση των υλικών που εξετάζονται. Έτσι προτείνεται ολοκληρωμένη διαδικασία και τεχνικές εξέτασης από την απόληψη των υλικών στο πεδίο έως την εκτέλεση δοκιμών προσδιορισμού των μηχανικών παραμέτρων. Η δειγματοληψία των σχηματισμών, επικεντρώθηκε στις λεκάνες ιζηματογένεσης του Κορινθιακού και του Πατραϊκού κόλπου, του Πύργου και της Καλαμάτας και αφορά ιζηματογενή πετρώματα Νεογενούς κυρίως ηλικίας από 28 διαφορετικά σημεία. Για τη συσχέτιση των μηχανικών χαρακτηριστικών των υλικών με τις περιοχές δειγματοληψίας, καταγράφονται και περιγράφονται συστηματικά οι θέσεις αυτές στο ευρύτερο γεωλογικό και τεχνικογεωλογικό περιβάλλον που εντάσσονται. Στη συνέχεια, ο προσδιορισμός των μηχανικών παραμέτρων πραγματοποιείται με την υλοποίηση και αξιολόγηση των αποτελεσμάτων από 31 δοκιμές τριαξονικής φόρτισης, ενώ η εργαστηριακή έρευνα επεκτείνεται και στον προσδιορισμό των δυναμικών παραμέτρων καθώς και των φυσικών χαρακτηριστικών. Επίσης, εξετάζεται η ορυκτολογία των υλικών αυτών με τη μέθοδο της περιθλασιμετρίας ακτίνων Χ και δίνονται ημιποσοτικοί προσδιορισμοί, στοιχεία απαραίτητα για την εξέταση της επίδρασης της ορυκτολογικής σύστασης στη μηχανική συμπεριφορά. Με βάση τα αποτελέσματα της εργαστηριακής έρευνας προσδιορίζεται κατ' αρχήν το πλαίσιο της συμπεριφοράς και των χαρακτηριστικών των υλικών αυτής της κατηγορίας. Εξετάζονται επίσης οι συσχετίσεις μεταξύ των μεγεθών και καθορίζονται οι μαθηματικές σχέσεις που τις ορίζουν. Επιπλέον διερευνάται και η εφαρμογή των δύο κύριων κριτηρίων θραύσης, Mohr-Coulomb και Hoek-Brown, μέσω της αξιοπιστίας τους στην απόδοση των πραγματικών εντατικών καταστάσεων, όπως αυτές προσδιορίστηκαν εργαστηριακά. Σημειώνεται πως όλες οι παραπάνω έρευνες πραγματοποιούνται με τη θεώρηση των υλικών ως μια ομάδα αλλά και διαχωρισμένα σε δύο επιμέρους κατηγορίες με βάση τη λιθολογική φάση τους, την ψαμμιτική και τη λεπτομερέστερη. Για τον καθορισμό, τέλος, της αντιστοιχίας της συμπεριφοράς των ενδιάμεσων αυτών υλικών με καθαρά βραχώδη υλικά, γίνεται η εξέταση των συσχετίσεων των μηχανικών τους παραμέτρων, αφού πρώτα συγκεντρώθηκαν όλα τα δεδομένα. Τα αποτελέσματα της συσχέτισης αυτής επιτρέπουν τη σύγκριση της συμπεριφοράς μεταξύ βράχων και ενδιάμεσων υλικών και αναδεικνύουν τη σημασία της εξέτασης των σκληρών εδαφών-μαλακών βράχων στην κατανόηση της συμπεριφοράς του πλήρους γεωτεχνικού φάσματος. / This thesis aims to the determination of the mechanical behaviour of geological formations which are classified as hard soils-soft rocks and are considered the intermediate transition from soil to rock. Formations of this type from Peloponnesus, Greece are examined. The first boundaries of this research have been set by recording the parameters of this type of geological formations as reported by previous researchers on this subject from the International and Greek experience. In the framework of this research, the ineluctability of examining in Greece hard soil-soft rock material behaviour by determining its mechanical properties based on a rock mechanics approach has been realized. Given the specific physis of hard soils-soft rocks there has been the need to focus on the methodology of sampling and laboratory testing and assess alterations in order to adjust them to the specialties of these certain formations. A complete sequence of methods and techniques is suggested, in order to achieve examination of the mechanical behaviour of these formations, including the steps from on site sampling to laboratory testing of mechanical properties. Sampling focused on the Peloponnesus area and more specifically on Korinth, Patras, Pyrgos and Kalamata sedimentary basins and refers to soft rocks of Neogene age from 28 different sites. Recording and systematic geological and geotechnical description of these sites of investigation has been conducted and the formations examined have been classified in their corresponding environment as far as their characteristics are concerned. 31 triaxial tests have been executed in order to determine the mechanical parameters of hard soils-soft rocks as part of a widened laboratory research which included all the mechanical and dynamical properties of these formations as well as physical parameters. Moreover, XRD testing has been included in order to provide information about the sample mineralogy and semi-quantitative analyses results were used as a means of evaluating the impact of mineralogy to the mechanical behaviour. The results of laboratory testing are used for addressing their range and typical values to the corresponding material type. Relationships between the parameters are also evaluated, resulting in empirical equations for the most strongly depended. Mohr-Coulomb and Hoek-Brown failure criteria were applied and their failure envelope fits to the true laboratory data are evaluated in order to compare them in terms of the best fit. All of the above are examined by considering the data as of corresponding to one (soft) rock type and also by considering the lithological differentiation of the sandy and finer types. Finally, the interdependence of the parameters describing mechanical behaviour was examined after taking in consideration data that refer to pure rock formations in order to reveal the equivalence in mechanical behaviour of the soft rocks to pure rocks. The results provide comparison between the intrinsic characteristics of these rock types and thus project the importance of hard soil-soft rock examination into understanding the mechanical behaviour of the full geotechnical spectrum.

AN ABSTRACT OF THE THESIS OF Behrooz Abbasi, for the Master of Science Degree in Mining and Mineral Resources Engineering, at Southern Illinois University Carbondale TITLE: A NUMERICAL ANALYSIS OF MINE INTERSECTIONS AND SUPPORT SYSTEMS FOR STABILITY MAJOR PROFESSOR: Dr. Yoginder P. Chugh Back ground: Partial extraction room-and-pillar mining systems provide about 60 % of the underground coal mined in the USA. This mining system develops 3-way and 4-way intersections. Rock falls related to fatal and nonfatal injuries in the USA for the period 2002 to 2007 identified that about 70% of these falls occur at intersections even though they represent only about 20-25 % of the area mined. A recent study on 2004 to 2008 roof-falls data base (RFDB) for Illinois mines, found that over 80% of these falls occurred at intersections. Thus, there is a significant need to improve stability of coal mine intersections if fatal and nonfatal injuries are to be controlled. The overall goal of this research is to develop an improved scientific understanding of stress distribution and instability around a 4-way intersection. An additional goal is to evaluate primary and secondary support layouts for improved stability around 4-way intersections. The following specific tasks were established for this research. * Perform 3-D numerical analyses to develop a better understanding of stress, strain and displacement distributions and associated instabilities around a 4-way intersection to identify ground support requirements. * Identify primary and secondary supports systems that may be suited to meet ground support requirements in (1) above. * Perform numerical analyses with identified primary and secondary supports installed to assess improvements in stability around an intersection. Analyses results show that pillar ribs across an intersection fail first and lead to progressive failure of immediate roof layers. The failure of immediate roof layers extends about 1.8m. In detail, coal ribs around the intersection corners mostly fail due to tensile stress, while roof and floor strata fail due to shear stresses and rib center fail due to combination of shear and tension mechanism. Primary supports significantly improve stability, but they are not adequate to ensure stability of four-way intersections. Secondary supports are needed to further improve stability of intersections. Also, based on the failure analysis a new secondary support system plan was proposed and analyzed.

Le massif de marbres de Saint-Béat se situe dans la Zone Interne Métamorphique des Pyrénées centrales françaises. Il est formé de sédiments mésozoïques métamorphisés lors de l'événement métamorphique extensif Haute température - Basse pression classiquement décrit dans les Pyrénées. L'objet de cette thèse est de caractériser la déformation ductile et la fracturation qui affectent ce massif, et de déterminer dans quelle mesure les processus responsables de la fracturation peuvent être influencés par l'état de déformation. Les caractéristiques de la déformation des marbres et de ses roches encaissantes seront déterminées essentiellement grâce aux orientations préférentielles des axes de la calcite (marbre) et du quartz (socle paléozoïque), déterminées à l'aide de mesures à l'EBSD. L'observation en lame mince des textures de la calcite permet de quantifier les taux de déformation et d'estimer la température de cette déformation. Combinés aux observations de terrain, ces résultats permettent de proposer un modèle structural retraçant l'évolution du bassin depuis l'extension aptio-albienne jusqu'à son état actuel. La fracturation du massif est ensuite regardée à différentes échelles, depuis la photo aérienne jusqu'à l'affleurement. Quatre zones seront étudiées en détail afin de classifier les fractures par familles de mêmes caractéristiques et de reconstituer localement les paléo-régimes de contraintes. On comparera les tenseurs obtenus avec les régimes tectoniques décrits dans la littérature. Trois faciès légèrement différents de marbre servent de base à une étude visant à discuter de l'état d'anisotropie de la roche. Ainsi, des essais en compression simple, en traction indirecte et des mesures de vitesses acoustiques sont pratiqués sur des carottes orientées réalisées dans ces trois faciès ; leurs résultats donnent accès aux caractéristiques internes de la roche. On comparera et discutera les résultats d'un faciès à l'autre, et au sein du même faciès, d'une orientation à l'autre. Les résultats obtenus sur la fracturation servent de guide à la classification des fractures observées sur les fronts de tirs, lors du creusement du tunnel routier de Saint-Béat, recoupant le massif sur plus d'un kilomètre du Nord au Sud. / The Saint-Béat massif, composed of different marble facies, is part of the Internal Metamorphic Zone of the French Central Pyrenees. It is formed by Mesozoic sediments metamorphosed by the High Temperature – Low Pressure extensional event, classically described in the Pyrenees. The aim of this work is to characterize the deformation and fractured state of the massif, and to understand how the former can constrain the latter. The ductile deformation state is recorded in calcite grains for Mesozoic rocks, or in quartz grains for Paleozoic rocks. Their preferential lattice orientations have been measured with the EBSD method. Calcite texture observations give indications about deformation rates and temperatures. These results, in addition with field observations, allow us to rebuild the structural evolution of the massif, from the Albian extension. Fracturing along the massif is described at different scales. Four outcrops are selected in order to characterize and to classify fractures, and locally reconstruct the paleo stress tensor. The obtained tensors are presented and compared to those already published. Three slightly different marble facies are used to discuss the degree of anisotropy of the rock. Mechanical experiments such as compression tests, tensile tests and velocity measurements of elastic waves are carried out on oriented cores within these three facies. These results provide internal rock characteristics which are discussed and compared for the three facies, and for different orientations of the cores.

Har du någonsin åkt genom en tunnel och undrat hur det kommer sig att det tunga berget över dig inte kollapsar in i detta hålrum? Har du lagt märke till underliga metallpinnar som sticker ut ur väggar och tak? Dessa metallpinnar är bultar, och de är en del av säkerhetsåtgärderna som ser till att tunnlar över hela Sverige är säkra att färdas i. När en tunnel byggs är det viktigt att ta reda på vilka egenskaper som berget har för att kunna avgöra hur stora säkerhetsåtgärder som bör implementeras. Dessa egenskaper kan vara sådant som sprickors utbredning och orientering, hur mycket vatten som finns i sprickorna, vad berget består av och krafter som påverkar berget. Säkerhetsarbetet kring tunnlar kan göra skillnaden mellan liv och död, men hur ska man forska kring detta? I ett labb kan man med hjälp av en modell undersöka vad som fungerar bäst, men även det minsta möjliga för att förhindra kollaps. I detta arbete har en modell som representerar ett tunneltak använts. Den används till undervisning för förståelse av bultar. Modellen var en upphöjd stålram med avtagbar botten, stålramen var kvadratisk med 82 cm sidolängd. I denna ram placerades skruvar och järnvägsmakadam för att simulera ett tunneltak med bultar i mindre skala. Järnvägsmakadam är krossat berg med en kornstorlek på ca 32 till 64 mm. Skruvarna trycker ihop makadamen med hjälp av brickor för att tryck ska uppstå och trycket mäts med tryckgivare som är placerade i modellen. Arbetet som har utförts med hjälp av modellen syftar till att utveckla metoder för hur sådana försök bör utföras i framtiden. Tidigare försök har gjorts och då har det observerats att denna modell har varit stabil när skruvarna spänts till 7 Nm (Newtonmeter) vridmoment och att den kollapsade av minimal påverkan när skruvarna spändes till 5 Nm. Därför gick vi in i detta arbete med hypotesen att modellens lägre gräns för stabilitet fanns strax under 5 Nm. Vid de tidigare försöken mättes inte trycket i modellen och vi hade därför ingen hypotes om detta. Försöken utfördes på olika vis. Skruvarna spändes i olika mönster och med olika vridmoment, makadamen placerades också på olika sätt när modellen byggdes upp. Som resultat ställdes vridmoment och tryck upp i tabeller och diagram. Det skulle visa sig att hypotesen om att den lägre gränsen var nära 5 Nm vridmoment inte stämde. Modellen hölls uppe även när skruvarna endast spändes till 2 Nm. Både när modellens bottenlager var fördelaktigt och ofördelaktigt uppbyggt ur ett stabilitetsperspektiv så höll modellen vid 2 Nm. Lägre vridmoment än 2 Nm kunde inte testas i brist på känsligare verktyg. / Have you ever traveled through a tunnel and wondered why the heavy rock above you doesn’t collapse on top of you? Have you noticed the odd metal rods that sticks out from the walls and ceiling? These metal rods are bolts, a part of the security measures that make sure that tunnels all over Sweden are safe to travel through. When a tunnel is built, it is important to know the properties of the rock to be able to assess what type of security measures that need to be applied. These properties can be fractures and their orientation, the composition of the rock and the forces that are present. The security work regarding tunnels can be the difference between life and death, but how can research in this field be carried out? Model experiments in a laboratory can be of great use to investigate the most efficient way to stabilize the rock, but also the minimal effort required to prevent collapse. For this report a model that represents the roof of a tunnel has been used. The model is used for learning about rock bolts and consisted of an elevated 82 cm square steel frame with a detachable floor. Bolts and crushed rock were placed within the frame to simulate a tunnel roof in a smaller scale. The crushed rock had a grain size of 32 to 64 mm. The bolts in combination with small metal discs compress the rock to produce pressure, and the induced pressure is measured with pressure indicators placed within the model. The experiments conducted with this model aims to develop potential new methods for future uses and experiments. Previous experiments with this type of model have shown that the model is stable when the bolts have been tightened to 7 Nm (Newton Meters) torque, and subsequently collapsed with minimal influence when the bolts were tightened to 5 Nm. Therefore, the hypothesis of this report was based on previous experiments, where the lower limit of the model seemed to be close to 5 Nm. The previous experiments didn’t measure the pressure throughout the strained rock mass, and therefore there is no hypothesis regarding this. The experiments were conducted in different ways. The bolts were tightened both in different patterns and with different torques, and the crushed rock were placed differently throughout the experiments as the model was being built. The following result of torque and pressure were presented in tables and graphs. The result showed that the hypothesis regarding the lower boundary being close to 5 Nm was not correct. The model stayed in place even when the bolts were tightened as low as 2 Nm. The model was stable at 2 Nm both with a favorable and unfavorable bottom layer of rock. Therefore, it is required to tension the bolt with torque lower than 2 Nm to determine the lower limit of stability, but that could not be tested due to the lack of proper tools.

The permeability of rocks has a critical influence on their fluid transport response in critical geo-environmental applications, such as pollutant transport or underground storage of hazardous nuclear waste. In such processes, the materials microstructure may be altered as a result of various stimuli, thereby impacting the fluid transfer properties. Stress or strain state modifications are one of the main causes for such evolutions. To numerically address this concern, an integrated and automated numerical tool was developed and illustrated on subsets of microCT scans of a Vosges sandstone (i) to explore the links between the pore space properties and the corresponding macroscopic transfer properties, with (ii) an incorporation of the microstructural alterations associated with stress state variations by using a realistic image-based representation of the microstructural morphology. The ductile mechanical deformation behavior under high confining pressures at the scale of the microstructure, inducing pore closures by local plastifications, was modelled using finite elements simulations with a non-linear elastoplastic law, allowing to take into account the redistribution of local stresses. These simulations require robust discretization tools to capture the complex geometry of the porous network and the corresponding solid boundaries of the heterogeneous microstructural geometries. To achieve this, an integrated approach for the conformal discretization of complex implicit geometries based on signed distance fields was developed, producing high quality meshes from both imaging techniques and computational RVE generation methodologies. This conforming discretization approach was compared with an incompatible mode-based framework using a non conforming approach. This comparison highlighted the complementarity of both methods, the former capturing the effect of more detailed geometrical features, while the latter is more flexible as it allows using the same (non conforming) mesh for potentially variable geometries.The evolution of permeability was evaluated at different confining pressure levels using the Lattice-Bolzmann method. This uncoupled solid-fluid interaction made it possible to study the combined influence on the permeability, porosity and the pores size distribution of the pore space morphology and the solid skeleton constitutive law parameters during loading and unloading conditions. The results highlight the need to consider elastoplastic laws and heterogeneities in the rock model to simulate the ductile behavior of rocks at high confining pressures leading to significant permeability alterations under loading, and irreversible alterations under loading/unloading cycles induced by progressive pore closures.The proposed methodology is designed to be flexible thanks to the interfacing with 'classical' discretization approaches and can be easily readapted to other contexts given the block approach. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

No description available.

<p>Crustal stress measurements play a crucial role in understanding how the subsurface deforms. As one of the most popular methods for stress characterization in deep wellbores, borehole breakout analysis examines the shape of drilling-induced compressive failures to determine stress directions and magnitudes, assuming that the rock formation is both isotropic and linearly elastic. To ensure accurate stress interpretations, the dissertation investigates the validity of underlying presumptions from two perspectives: (1) the effect of rock anisotropy (i.e., elastic anisotropy, and strength anisotropy) on wellbore failure patterns; and (2) the characterization of rock nonlinear elastic mechanical behaviors. </p> <p>The developed computer program, <em><strong>EASAfail</strong></em>, has broad applicability in calculating wellbore failure patterns for a wide range of scenarios. It takes into account factors such as elastic stiffness matrices of the rock, stress tensors in the surrounding environment, and the presence of weak planes. The program's generality allows it to handle various rock types with different degrees of symmetry in their elastic properties, as well as weak planes that are weaker than the intact rock matrix. By analyzing these factors, the program reveals that the patterns of wellbore failure in elastic and strength anisotropic rock formations are highly influenced by the sliding of weak planes. Complications from two modes of borehole failure, either in the intact rock matrix or in the weak planes, can cause the breakout azimuth to deviate from the direction of the minimum horizontal stress. </p> <p>In addition to hypothetical scenarios generated from numerical models, a case study from the field is presented to underscore the impact of foliations on the anomalous rotations of breakout azimuths. The wellbore was located in Northeastern Alberta, Canada, transecting both the sedimentary column and crystalline basement. Breakout rotations identified from caliper and image logs were highly likely caused by the slippage along foliations, supported by the close correlation between breakout azimuths and dip directions of foliations as well as polarization directions analyzed from dipole sonic logs. Stress magnitudes constrained from Monte Carlo simulations further reveal a lower stress field when rock anisotropy is taken into account, compared to what is inferred conventionally. </p> <p>The characterization of rock nonlinear elasticity involves the utilization of the third-order elastic (TOE) model. To measure the TOE moduli in a static manner, test-specific protocols were proposed based on the nonlinear stress-strain behaviors of the rock. By arranging the stress-strain responses obtained from hydrostatic, uniaxial, and triaxial compressive tests into a linear system of equations, it becomes possible to invert the equations for the TOE moduli. These analytical equations were validated through calculations from finite element models. </p> <p>By employing the established protocols, the TOE moduli were derived for four different rock types with varying pore structures when subjected to hydrostatic and uniaxial compressions. The TOE model successfully captured the nonlinear stress-strain responses exhibited by Indiana limestone, Vif-type Fontainebleau sandstone, and Snake River Plain basalt. However, it was found to be inadequate for Franc-type Fontainebleau sandstone, which displayed noticeable hysteresis and experienced significant strains. Future geomechanical applications will undoubtedly gain advantages from utilizing the inverted TOE moduli obtained through static measurements, as they allow for the examination of the impacts of nonlinear elasticity in rocks. </p>

Thesis (MEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The suitability of local construction materials for construction purposes is governed by several rock mechanical properties. Strength, durability, performance and petrography of aggregates all influence the decisions engineers make in deciding if the aggregate is suitable and sustainable throughout the lifetime of a structure. This thesis investigates these properties by combining engineering, chemistry and geological disciplines to make informed decisions. The pertaining project for which the research was conducted is the construction of the gravimeter vault at the Matjiesfontein Geodesy and Earth Observation Observatory (MGO) although the research acquired can be used for other projects of a similar nature and other outbuildings at the MGO. Material at and around the site were tested for strength and durability according to certain South African National Standards (SANS). Slake durability was tested as certain rock types tend to slake when exposed to the atmosphere such as tillite of the Dwyka formation and shale of the Karoo Supergroup. Concrete cube strength was determined on cubes containing crushed rock from Matjiesfontein as well as river sand. Cube strength was conducted to analyse performance and to establish a mix design that would be sustainable throughout the lifetime of the project. Petrographic examination using Powder X-ray diffraction (PXRD), X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM) and inspection under a petrographic microscope were conducted. These methods were used to determine if a risk exists for alkali-silica reactivity (ASR) in concrete when the rock types are used as aggregate, particularly if high quartz-bearing rock types such as quartzite of the Table Mountain group were to be used as coarse aggregate. Inspection of thin sections for strained quartz under a petrographic microscope and SEM imaging were important in determining if ASR may occur. The gravimeter vault was constructed using materials sourced mainly from Laingsburg. Tillite satisfied all tests and analyses conducted during the research, making it more suitable for construction than the other materials from Matjiesfontein. The slake durability test indicates that tillite is nearly as durable as quartzite, which is considered the most durable rock type at Matjiesfontein. This is due to atmospheric conditions in the Karoo being very dry with low humidity in comparison to the coast where slaking is known to occur. Slaking properties were most prominent for shale at Matjiesfontein and if excavated, it is recommended to cover the exposed shale with a layer of asphalt or cement to prevent slaking. The 10% fines aggregate crushing test (10%FACT) value for tillite was over the 210 kN prerequisite and the wet-to-dry ratio over 75% making it suitable for road construction according to the 10%FACT. All cube tests reached the desired 40 MPa prerequisite although the mixtures containing local river sand were unworkable. Unlike quartzite and quartzitic sandstone from Matjiesfontein, tillite is low in quartz and has minimal strained quartz. Therefore, no risk exists for ASR if tillite were to be used as aggregate in concrete. / AFRIKAANSE OPSOMMING: Die geskiktheid van plaaslike konstruksiemateriale vir konstruksiedoeleindes word deur sekere rots meganiese eienskappe beïnvloed. Sterkte, duursaamheid, volhoubaarheid en petrografie van aggregaat beïnvloed die besluite wat ingenieurs moet neem sodat die aggregaat aan standaarde voldoen en gedurende die leeftyd van ‘n struktuur volhoubaar is. Hierdie tesis ondersoek die genoemde eienskappe deur ingenieurs-, chemiese- en geologiese dissiplines te kombineer. Die voorgenome projek, waarvoor die navorsing ter sprake is, is vir die konstruksie van die gravimeterkluis by die “Matjiesfontein Geodesy and Earth Observation Observatory (MGO)”, alhoewel die navorsing ook gebruik kan word vir soortgelyke projekte, sowel as die konstruksie van die res van die geboue by die MGO. Materiale van die terrein en die omgewing is volgens sekere Suid-Afrikaanse kodes vir sterkte en duursaamheid getoets. Die blusbaarheid van materiale is getoets omdat sekere materiale, soos tilliet van die Dwyka-formasie en skalie van die Karoo Supergroep blus wanneer dit aan die atmosfeer blootgestel word. Die betonsterkte van kubusse, waarin plaaslike gesteentes en riviersand van Matjiesfontein vir aggregaat gebruik is, is bepaal. Die kubusse is getoets om die sterkte daarvan te analiseer en om ‘n betonmengsel, wat tydens die leeftyd van die projek volhoubaar is, daar te stel. Petrografiese eksaminering deur X-straal difraksie (XRD), X-straal fluoressensie (XRF), Skandeerelektronmikroskopie (SEM) en inspeksie onder ‘n petrografiese mikroskoop is gedoen. Met die doel om die petrografiese samestelling van materiale van Matjiesfontein te bepaal, is hierdie metodes gevolg om te uit te vind of daar ‘n risiko vir alkalie-silikaat reaksies (ASR) bestaan, as die gesteentes in beton gebruik word. Veral gesteentes met ‘n hoë hoeveelheid kwarts, soos kwartsiet van die Tafelberg-groep, is hier ter sprake. Inspeksie van dunsnitte vir gespanne kwarts onder ‘n petrografiese mikroskoop en SEM was belangrik om die risiko vir ASR te bepaal. Die gravimeterkluis is hoofsaaklik met materiale afkomstig van Laingsburg gebou. In vergelyking met die ander gesteentes by Matjiesfontein is tilliet, volgens alle toetsparameters, die mees geskikte gesteente vir konstruksiedoeleindes. Die blusbaarheid van tilliet vergelyk goed met kwartsiet, wat as die sterkste en duursaamste gesteente by Matjiesfontein, beskou word. Die rede hiervoor is die atmosferiese toestande wat baie droër is, asook die laer humiditeit in die Karoo, in vergelyking met gebiede nader aan die kus waar blusting meer algemeen voorkom. Die blusbaarheid van skalie by Matjiesfontein kom algemeen voor. As daar dus uitgrawing in hierdie gebied plaasvind, word dit aanbeveel dat ‘n laag sement of asfalt oorgegooi word om die blusting te verhoed. Die 10%FACT waarde vir tilliet was bo die vereiste 210 kN, asook bo die 75% nat-teenoor-droog-verhouding en daarom is dit volgens die 10%FACT-toets as padboumateriaal geskik. Alhoewel mengsels, wat plaaslike riviersand bevat het, onwerkbaar was, het alle toetsmonsters (kubusse) die vereiste 40 MPa- sterkte bereik. In vergelyking met kwartsiet en kwarsitiese sandsteen, bevat tilliet min kwarts en ook minimale gespanne kwarts. Daar bestaan dus geen risiko vir ASR indien tilliet van Matjiesfontien in die beton gebruik word nie.

Projetos de estabilidade de escavações mineiras por meio de estudos de caracterização do maciço rochoso com o uso da mecânica de rochas são indispensáveis para otimizar o aproveitamento das jazidas, garantir segurança nas operações de lavra e minimizar os impactos ambientais decorrentes da instabilidade dos taludes da cava. Nesta dissertação utilizou-se de critérios recentes de ruptura em rocha, para obtenção de dados de entrada em métodos já clássicos de análise da estabilidade de taludes em maciços rochosos para a cava de dolomito lavrada a céu aberto. Os critérios utilizados serão avaliados com relação à compatibilidade dos resultados obtidos com sua aplicação e a coerência com a situação atual observada na lavra em desenvolvimento. Análises sobre a paralisação da lavra em decorrência dos problemas de instabilidade também serão avaliadas e discutidas. Para ilustrar esta dissertação foi eleita a jazida de dolomito localizada no Sinclinal do Gandarela em virtude dos problemas de instabilidade encontrados na cava. As conclusões finais são apresentadas nos últimos itens deste trabalho. / The design of stable excavations using rock masses characterization with the tools provided by rock mechanics, are indispensable for optimizing the economic exploitation of ore deposits, to ensure the safety in the mining works and to minimize the environmental impacts deriving of the open pit slopes instability. In this Dissertation, for obtain the input data for classic methods of rocky slopes stability analyses, it is used the most recent criteria of rock mass failure applied for an open pit mine of dolomite. The utilized criteria compatibility will be evaluated by the results obtained with their utilization and the coherence with the real situation verified at the developing mine. Will be evaluated and discussed the analyses about the stoppage of the mine works due to the slope instability problems. To illustrate this Dissertation are elected a dolomite ore deposit situated at the Gandarela Synclinal on account of the instability problems that occurred in the mine pit. The final conclusions are listed in the items presented at the end of this work.