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ABSTRACT: Remote sensing methods attempt to derive quantitative estimates for the rock properties and, simultaneously, to evaluate their distribution in the subsurface space. The characterization of the subsurface structures has a wider scope than only inferring a geometrical model of detectable rock features. Relevant questions are whether geophysics can also produce information regarding the character of the features detected and, whether this information can be included to a cohesive interdisciplinary representation of the rockmass. The wave methods are considered as representative for the remote sensing group. The discussion will refer mainly to general features of remote sensing, common to both seismic and electromagnetic waves. The physical phenomena being different for the two cases, some specific aspects will be discussed separately. Two ways of decreasing the uncertainty related to the remote sensing results are reviewed: achieving a more extensive and better controlled coverage of the investigation volume and investigating in more detail the significance of the parameters determined. The characterization of the subsurface space is a complex task involving several disciplines. Therefore, it is necessary that an interdiciplinary body of knowledge is formed, including the contributions of various disciplines. 1 INTRODUCTION In Geophysics, remote sensing designates a group techniques of data acquisition, processing and interpretation, used to determine local physical properties of the rock, at a certain distance from the observation point. The meaning of local may vary widely with the experimental scale and method. Here, local will refer to the smallest spatial element where a certain physical property of the rock can be evaluated independently. This will also define the resolution. A distinctive feature of remote sensing, compared to direct observation, is the attempt to derive quantitative estimates for the rock properties and, simultaneously, to evaluate their distribution in the subsurface space. The duality of the remote sensing approach requires the support of a theory, to explain the basic phenomenology of the experiment, and of a powerful computational apparatus, for solving the laborious problem of the systemic representation of spatial distributions. If the distributions of the rock properties display continuity and order, which can be logically related to a physical state, the nature and the geological history of the rock, the subsurface space can be represented as a set of subsurface structures. The characterization of the subsurface structures has a wider scope than only inferring a geometrical model of detectable rock features. Relevant questions are whether geophysics can also produce information regarding the character of the features detected and, whether this information can be included to a cohesive interdisciplinary representation of the rockmass. The main factor hindering the interdisciplinary integration is the lack of a consistent theory able to express non-ambiguously quantitative relations between the measurables of various disciplines. Such relations are usually derived by interpretations involving empiric formulae, extrapolations and logical inference. Interpretive approaches are justified as the last stages of cognitive exercises, when they provide the conceptual frames for the understanding of the of the experimental results. When further processing of the integrated data is needed.
- Geophysics > Electromagnetic Surveying (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.46)
ABSTRACT: The principles of critical state mechanics appear to apply for shales. The isotropic consolidation behavior of four shales have been investigated experimentally at effective pressures of 1to 65 MPa to evaluate some critical state parameters as a function of mineralogy and porosity. Sample volume change as a function of effective pressure was measured to determine the normal consolidation (NCL) and over consolidation (OCL) lines. The slopes of the NCL and OCL (and) are distinct for the four shales. The slopes of the NCL correlate strongly with porosity and with the sum of porosity and swelling clay content, i.e. the water sources. The slopes of the OCL correlate with non-swelling minerals (clays and non-clays), i.e. the elastic components. The results suggest that careful mineralogical and porosity characterizations may be used to estimate both isotropic consolidation and deformation parameters of shales. RESUME: Les principes de la mecanique à l'etat critique sont applicables egalement aux schistes. Dans un appareil triaxial on a etudie le comportement de consolidation isotrope de quatre schistes A des pressions effectives de 1 à 65 MPa, afin d'etudier leur caracteristiques en fonction de leur mineralogie et de leur porosite. Le changement de volume de l'echantillon en fonction de la pression effective a permis de determiner les courbes de consolidation normale (NCL) et de sur-consolidation (OCL). Les pentes des courbes NCL et OCL (et) sont distinctes pour les quatre schistes. Le pente de la courbe NCL est en forte correlation avec la porosite, ainsi qu'avec la somme de la porosite et du contenu en argile gonflante, la principale provenance d'eau. La courbe OCL est en correlation avec la teneur en mineraux argileux nongonflants et mineraux non-argileux qui representent les composants elastiques. Π en resulte qu'une caracterisation soigneuse de la mineralogic et de la porosite des schistes permet de connaître leur comportement de consolidation isotrope et de deformation. ZUSAMMENFASSUNG: Die Grundsatze der Kritischen-Zustands-Mechanik sind auf Tongesteine unterschiedlicher Zusammensetzung anwendbar. In einem Triaxialapparat wurde das isotrope Konsolidationsverhalten von 4 Tongesteinen bei effektiven Spannungen von 1–65 MPa bestimmt. Die kritischen Zustandsparameter wurden dabei in Abhangigkeit von Mineralogie und Porositat ermittelt. Die Messung der Volumenanderung in Abhangigkeit der effektiven Spannungen erlaubte die Bestimmung der Pfade der Erstbelastung (NCL) und der Wiederbelastung (OCL) sowie ihrer Steigungen. Die NCL-Steigung korreliert streng mit der Porositat, sowie der Summe von Porositat und Anteil quellfahiger Tonminerale, welche den Wassereinfluss reprasentieren. Die OCL-Steigung korreliert mit dem Anteil der nicht quellfahigen Tonminerale und Nichttonmineralien, welche die elastischen Komponenten darstellen. Daraus resultiert, dass sie genaue Charakterisierung der Mineralogie und der Porositat der Tongesteine die Beurteilung des Konsolidations- und Deformationsverhaltens ermöglicht. 1. INTRODUCTION Shales make up over 75% of sedimentary rocks near the Earth's surface. They are often encountered when excavating foundations and tunnels and are important liners for hazardous waste repositories. Shales are also the most common caprock for oil and gas reservoirs. Clays have been proposed as a possible host medium for the geological disposal of radioactive waste (e.g. Chapman, 1984). Failure of shale formations in repositories. tunnels and wells can increase drilling costs dramatically (e.g. Steiger and Leung, 1988). The prediction of wellbore stability in shale is one of the most important needs in the petroleum industry. Quantitative determination of physical properties of shales are necessary to constrain models of compaction and deformation of these important sedimentary rocks. Isotropic consolidation data are used in models that predict drainage in low permeability shales (e.g. Savage and Braddock, 1991) and models that make risk analyses of ground water movement near hazardous wastes. Using clay compression experiments that related porosity to burial, Skempton (1970) demonstrated that the relation between void ratio and log overpressure is essentially linear for any clay. Moreover, at a given overburden pressure the porosity (void ratio) depends on the amount and type of clay minerals.
- Europe > Switzerland (0.29)
- North America > United States (0.28)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Mineral (1.00)
ABSTRACT: The aim of this study is to develop models for predicting mechanical properties of shales using available index parameters. Regression analyses have been carried out between index parameters and mechanical properties, both for statistical prediction purposes and for curve fitting of the available experimental data. Such correlations may be of use to geotechnical and mining engineers, in providing preliminary estimates of shale mechanical properties and perhaps reduce testing requirements especially, when samples of adequate size for testing are generally not available. RESUME: Le but de cette etude est de developper des modèles pour prevoir les proprietes mechaniques des schistes en utilisant les "paramètres index" disponibles. Des analyses de regression ont tee effectuees comparant "paramètres index" et proprietes mechaniques, à la fois dans le dessein de previsions statistiques et pour l' adaptation aux courbes des donnees disponibles. De telles correlations peuvent être utiles pour des ingenieurs des mines ou de geotechnique, en procurrant des estimations prealables des proprietes mechaniques des schistes et peut-être la reduction des tests requis, specialement dans les cas où des echantillons de tailles adequates pour les tests ne sont pas generalement disponibles. ZUSAMMENFASSUNG: Das Ziel dieser Studie ist es, Modelle zu entwickeln, die die mechanischen Eigenschaften von Schiefer anhand von verfuegbaren Indexparameten voraussagen. Um statistische Voraussagen treffen zn können und experimentel erworbene Daten anzupassen, sind Regressionsanalysen zwischen Indexparametern und mechanischen Eigenschaften durchgefuehrt worden. Eine solche Korrelation könnte fuer Geotechniker und Bergbauingeniere von Nutzem sein, indem sie im voraus schatzwerte fuer die mechanischen Eigenschaften von Schiefer ermöglicht. Es könnten dadurch die Testanforderungen fàr die falle verringert werden, in denen keine Proben der geforderten Testgröβe vorhanden sind. 1 INTRODUCTION Shales account for nearly 70% of the total sedimentary cover of the crust exposed at the surface of the earth (Press and Siever, 1974). Furthermore they are common in engineering projects, as construction materials for shale fills and embankments, and in their natural and undisturbed state in foundations, cut slopes, and tunnels. Despite the fact that knowledge of the mechanical properties of shale is important, little research has been conducted on shales in comparison with other sedimentary materials such as carbonate rocks and sandstones. One of the main reasons for this lack of research is perhaps the difficulty in working with shale, since it is difficult to sample and store it. Furthermore, the measurement of mineralogical and mechanical properties is complicated by the extremely fine grain size and the large clay content as well as the fact that it disintegrates in water. The research presented in this paper was undertaken to generate statistical relationships between index properties that are relatively easy to measure and mechanical properties that are difficult to determine. These correlations may aid engineers to make preliminary estimates of the mechanical properties of shales. 2 COLLECTION AND STORAGE OF DATA Data have been extracted from available published information such as: journals, conference proceedings, technical reports, books, as well as from our own experimental results. If errors or unexplained discrepancies were detected in the results of laboratory and field tests, these data were excluded specifically if they were significantly out of the range of all other published values. A database (SHALEDATA) has been developed to store the data in an easily used database format (Lashkaripour and Passaris, 1994). The database is a collection of data of hundreds of items of geological information, physical and mechanical properties of different types of shales that range from hard siltstone to soft clayshale. The reference data points at the time of writing were exceeding 450 entries. and in view of the further developments it is expected that the database will comprise 500 entries. 3 CORRELATION BETWEEN INDEX PROPERTIES AND MECHANICAL PROPERTIES Statistical analyses were applied to evaluate the available data and to obtain the best correlation between index parameters and mechanical properties. High correlations exist between water content, porosity, point load index, tensile strength and modulus of elasticity with uniaxial compressive strength, whereas correlations between density, elastic wave velocities (Vp and Vs) and Poisson's ratio with compressive strength are poor.
Three-dimensional Tomographic Visuallzatlon of Natural Fracture Networks And Graph Theory Analysis of the Transport Properties
Pyrak-Nolte, Laura J. (Department of Civil Engineering and Geological Sciences, University of Notre Dame, Ind.) | Montemagno, Carlo D. (Department of Civil Engineering and Geological Sciences, University of Notre Dame, Ind) | Yang, Gemei (Department of Materials Science and Mineral Engineering, University of California, Berkeley, Calif) | Cook, Neville G. (Department of Materials Science and Mineral Engineering, University of California, Berkeley, Calif) | Myer, Larry R. (Earth Sciences Division, Lawrence Berkeley Laboratory, Calif)
ABSTRACT: We analyze the spatial persistence of fracture network porosity and mean network aperture over the length of core samples containing natural fracture networks. By combining medical imaging algorithms with a Wood's metal injection technique, the three dimensional geometry of fracture networks subjected to reservoir conditions is visualized and analyzed. The transport properties of the reconstructed fracture network geometry is analyzed using graph theory to examine the capillary pressure-saturation relationship for the network. RESUME: Les resultats d'une etude complete en laboratoire du tridimensionnel geometrie de la reseau de fractures sont resume et analyses. Une technique d'injection de metal est utilise avec une technique de Medical Imaging, elle fournit des resultats quantitatifs sur l'exacte geometric des reseau de fractures. ZUSAMMENFASSUNG: Wir analysieren die raumliche Bestandigkeit der Porositat einigem Kluftnetz in Steinkohle, und auch die durchschnittliche Öffnung diesen Kluftnetz. Diese Drei-Dimensionalen Eigenschaften sind erzielen durch ein Metaleinspritz-verfahren, susammen mit Medizinische Abblidung. Hydraulische Eigenschaften dem Kluftnetz sind computiert durch Graph Theorie. 1 INTRODUCTION: Fracture network geometry influences the stability of rock masses and controls the movement of fluids through the rock mass. Fracture networks in rocks are often observed in only two dimensional cross-sections such as at rock outcroppings, tunnel walls, and boreholes. Observing the three-dimensional network geometry is difficult especially with depth. At issue is whether or not the observed two-dimensional topology can be extended into the rock mass or with depth into the earth. Because of lithostatic stresses and local stress regimes, the spatial persistence of fracture network geometry would be expected to be affected with depth because fractures that are open at the surface may be closed or may not exist at depth. The difficulty has been in quantifying the spatial persistence in network geometry and such basic properties as network porosity. Remote techniques such as cross-hole seismic tomography may indicate that a fracture network still exists at depth but cannot indicate interconnectivity or whether it will support flow. The cross-hole tomographic results are often correlated with surface expressions of fracture networks to predict subsurface behavior. In this paper, we analyze the spatial persistence of fracture network porosity and mean network aperture over the length of core samples containing natural fracture networks. By combining medical imaging algorithms with a Wood's metal injection technique, the three-dimensional geometry of fracture networks subjected to reservoir conditions is visualized and analyzed. The transport properties of the reconstructed fracture network geometry is analyzed using graph theory to examine the capillary pressure saturation relationship for the network. 2 Experimental Procedure 2.1 Samples Four samples were used to investigate the geometrical properties of natural fracture networks (cleats) in coal. Samples lC2 and BC7A are whole drill core from the Intermediate and Basal Fruitland Formation, respectively, from the Valencia Canyon So. Ute #32–1 well, San Juan Basin. La Plata County, Colorado. Samples AA and BB were cored from blocks of coal from Seam #1 in the Sundance Pit at the La Plata coal mine, San Juan County, New Mexico. Core AA was taken perpendicular to the bedding planes. 2.2 Experimental Set-up The porosity of the fracture network was measured using a Wood's metal injection method and a water-helium drive method. In the water-helium drive method, the coal core is saturated with a brine and subsequently displaced with humidified helium. The volume of brine produced is recorded and used to establish the porosity of the sample (Gash 1991; Gash 1992).
- North America > United States > Texas > Colorado County (0.24)
- North America > United States > Colorado > La Plata County (0.24)
- North America > United States > New Mexico > San Juan County (0.24)
- Geology > Geological Subdiscipline > Geomechanics (0.95)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.34)
- North America > United States > New Mexico > San Juan Basin > Fruitland Formation (0.99)
- North America > United States > Colorado > San Juan Basin (0.99)
- North America > United States > Arizona > San Juan Basin (0.99)
Thermal Behavior of Rock Mass Around Openings Affected By Low Temperature
Inada, Yoshinori (Department of Civil and Ocean Engineering, Ehime University, Matsuyama) | Kinoshita, Naoki (Department of Civil and Ocean Engineering, Ehime University, Matsuyama) | Seki, Shozo (Department of Civil and Ocean Engineering, Ehime University, Matsuyama)
ABSTRACT: It is supposed that the thermal behavior of rock mass around openings when low temperature materials are stored in openings will be different with each type of rock. In this study, the results of the investigation of the physical properties of rocks in wet state under low temperatures by experiment are described. Using these values, temperature distribution and behavior of rock mass around openings were analysed theoretically and the results which were discussed for mechanism of crack development are described. In the case of granite and sandstone, it was found that cracks were caused by tensile stress due to shrinkage of rock mass. On the other hand, in the case of tuff and mudstone, cracks were caused by shearing stress due to expansion of ice when water changed to ice. Finally, as one of the ways prevent leakage, the results in which the surface of openings was coated with resin, that is the "resin lining system" is discussed. RESUME: Dans le cadre du stockage souterrain à basse temperature, on suppose que le comportement thermique de la masse rocheuse environnant la cavite varie d'une roche à l'autre. Get article fait etat des resultats obtenus dans le cadre des etudes experimentales concernant les proprietes physiques des roches à l'etat humide et sous basses temperatures. Sur la base de ces valeurs, nous analysons d'un point de vue theorique la repartition de temperature et le comportement thermique de la masse rocheuse à proximite de la cavite, puis nous effetuons une discussion sur les mecanismes de developpment des fissures. Dans les granites et les gres, nous avons mis en evidence le fait que les fissures apparaissent à la faueur des tensions dues à la compression de la masse rocheuse. D'autre part, dans les tufs et les marnes, les fissures sont causes par le cisaillement qu'induit l'expansion de la glace lors de la solidification de l'eau: Enfin; en tant qu'autre methode dite du "masque de resine" qui consiste à recouvrir de resine les parois de la cavite. ZUSAMMENFASSUNG: Es wird angenommen, daβ bei lagerung won Material tiefer Temperatur in Höhlen das Warmeverhalten der Felsmassen um die Höhle herum je nach der Felsart verschieden ist. In dieser Forchung werden die Ergebnisse der experimeniellen Untersuchung der physikalischen Eigenschaften von Felsen im nassen Zustand unter tiefen Temperaturen beschrieben. Diese Werle werden verwendet, um die Temperatueverteilung und das Warmeverhalten der Felsmassen um Höhlen herum theoretiscb zu analysieren; und die Ergebnisse der Betrachtungen ueber den Entstehungsmechanismus von Rissen werden beschrieben. In anderen Worten heiβt dies, daβ Risse bei Granit und Sandstein durch Zugspannungen auf Grund von Schrumpfung der Felsmasse uerursacht werden, wahrend sie bei Kalktuff und Pelit durch die beim Gefrieren von Wasser zu Eis verursachte Scherspannung auf Grund der Schwellung verursacht werden. Als eine weitere Methode zur Beschichtung der Höhlenoberflache mit Harz, d.h. eine "Harzbeschichtungsmethode" angestellt. 1. Introduction Recently the supply and demand quantity of LNG and LPG as substitutes for oil energy has a tendency to increase. Frozen food also shows a similar tendency with the increase of two income families, and the great variety and rapid increase of frozen food. With these points as background, it is expected there will be an increase in storage establishments in the near future. From the view point of multiple-utilization of land in Japan (which has little available land), also reduction of heat loss and maintenance cost, environmental safeguards, utilization of underground openings excavated in mountains should be considered.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.62)
- Geology > Rock Type > Igneous Rock > Granite (0.50)