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ABSTRACT: This study was conducted as part of research concerned with borehole failures caused by shale materials during reservoir-related drilling activities. The examination of a particular shale of known mineralogical characteristics was completed to develop basic physical relationships between strength, p-wave velocity and moisture content The application of these relationships may lead to the prevention of drilling difficulties and the resultant increases in initial drilling costs associated with drilling through shales. Triaxial and uniaxial compression testing of the Pierre I shale indicates that as moisture levels in the shale increase, the strength decreases polynomially relating to burial depth, while p-wave velocity varies inversely and linearly with moisture content. RÉSUMÉ: Cette etude a ete effectuee dans Ie cadre de recherches sur l'effondrement de trous de forage cause par des meteriaux argileux durant Ie forage de reservoir. L'examen d'une argile particulière, dont les characteristiques mineralogiques sont connues, a ete complète pour etablir les relations physiques de base entre Ie force, la velocite des ondes Pet la teneur en eau. L'application de ces relations pourrait conduire à la prevention des difficultes, reliees au forage dans des materiaux argileux, et des accroissements des coûts initiaux de forage qui en resultent. Des essais de compression triaxiaux et uniaxiaux des argiles Pierre I indiquent que lorsque la teneur en eau d'une argile augmente, la force decroît de facon polynomiale en fonction de la profondeur d'enfouissement, alors que la velocite des on des P varie de facon inverse et lineaire à la teneur en eau. ZUSAMMENFASSUNG: Diese Forschungsarbeit liefert einen Beitrag zum besseren Verstandnis von Bohrlochinstabilitaten, die durch das Antreffen von Schiefer beim Bohren nach fossilen Brennstoffen verursacht werden. Ein Schiefer bekannter Zusammensetzung wurde untersucht, urn grundlegende Zusammenhange zwischen Festigkeit und DruckweLlenausbreitungsgeschwindigkeit in Abhangigkeit vom Feuchtigkeitsgehalt mathematisch zu beschreiben, Die Beruecksichtigung dieser Zusammenhange kann Bohrschwierigkeiten verrneiden und so die Bohrkosten senken. Die mit dem 'Pierre I' Schiefer durchgefuehrten triaxialen und monoaxialen Drucktests zeigten, daß die Festigkeit als Funktion der Bodentiefe mit Zunehmendem Feuchtigkeitsgehalt abnimmL Die DruckweIJenausbreitungsgeschwindigkeit nimmt linear mit stelgendem Feuchtigkeitsgehalt abo 1 INTRODUCTION This study is composed of sections dealing with the particular shale that was tested, the method of control of moisture content, the testing procedure, the results of the moisture content control, the results of the testing in terms of strength and p-wave velocities, and the equations which are proposed that relate the two latter parameters to the measurable moisture content of the shale in question. 2 BACKGROUND MATERIALS The procedure for performing tests required stringent controls on the homogeneity of the shale, and detailed monitoring during all stages of test preparation. The shale of interest during this test program was the Pierre I, with a clay to quartz ratio of 4.7. The Pierre I was chosen as an end member representative of the swelling, gumbo, or smectitic shales which are encountered in borehole drilling situations often resulting in stuck pipe. A similar study is currently being carried out on the Mancos Shale (a quartz-illite shale) which will aid in The Pierre 1 is an Upper Cretaceous marine shale from the Great Plains region of the northwestern United States. It is found relatively near the surface and outcrops in such states as Colorado (Chenevert, McKown et. a1.). Its dark grey colour and visible laminations give it a typical shale appearance and it is used by many researchers (A.H. Hale, F.K. Mody, M.E. Chenevert, C. Deem, R.P. Steiger). This formation spans a large physical region and is relatively uniform in moisture content, mineralogy, grain size, bedding thickness and CEC. The Pierre I shale is not buried too deeply and is fairly easy to recover in large amounts compared to offshore shales. Because of this, and its similarity of mineralogy to many other shales encountered during deep borehole drilling, it is an ideal shale to use as an end-member mineralogically and mechanically. 3 PROCEDURES 3.1 Equilibration with OBMs Moisture content alteration was carried out by submersing samples in an oil based mud (OBM) which was constantly circulated to maintain an equal distribution of fluid over the samples. The salinity of the water portion of this mud was used to maintain the Relative Humidity (RH) at a constant level within the sealed chamber. The difference in RH values between the shale samples and the surrounding fluid induced either hydration or dehydration of the samples, and thus, changes in the moisture content of the samples. Processes involved in this equilibration are assumed to be the driving force of concentration gradients, the resistance of pore channels to flow, and the driving force of a humidity gradient.
- North America > United States > New Mexico > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- North America > United States > Colorado > San Juan Basin > San Juan Basin Field > Mancos Formation (0.99)
- Well Drilling > Drilling Operations (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.78)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.69)
- Well Drilling > Wellbore Design > Wellbore integrity (0.66)
ABSTRACT: This paper presents a study of experimental data on different shales available in the literature and from several shales tested at NGI. A database of shale properties was created and a study was conducted in order to determine which parameters control the strength of shales. Correlations of shale strength were made with index properties, overconsolidation ratio (OCR), and illite to smectite (I/S) ratio for different shales. The index properties give an indication of the composition of the shale, OCR reflects the degree of compaction a shale deposit has undergone, and the I/S ratio serves as a measure of the degree of diagenesis of the shale deposit. The strength of many shales can be correlated with index properties like porosity and plasticity index. The undrained shear strength normalized with respect to the current in-situ effective stress correlate well with OCR but not with l/S ratio. However, it was found that diagenesis induces an apparent increase in pre-consolidation of a shale deposit. Consequently, older and more cemented shales have much higher apparent OCR than younger and uncemented samples. The paper demonstrates that the SHANSEP procedure used for clays may also be adapted for estimating the undrained shear strength of most shales. RESUME: Cet article presente une etude des donnees experimentales sur differents schistes argileux. Les donnees proviennent de la litterature et d'essais de laboratoire faits au NGI. Une base de donnees des caracteristiques des schistes argileux a ete creee. L'etude a ete faite pour determiner les parametres qui contrôlent la resistance au cisaillement des schistes argileux. Des correlations ont ete etablies entre resistance au cisaillement et proprietes indices, surconsolidation (OCR) et rapport de la composition illite-smectite (I/S) pour les differents schistes argileux etudies. Les proprietes indices sont utiles pour determiner la composition des schistes argileux, la surconsolidation reflète Ie degre de compaction de la formation, et Ie rapport I/S est une mesure du degre de diagenèse de la formation. La resistance au cisaillement de plusieurs schistes argileux se corrèle avec les caracteristiques indices comme la porosite et I'indice de plasticite. La resistance au cisaillement non-drainee normalisee à la contrainte effective in situ se corrèle bien avec la surconsolidation (OCR), mais pas avec Ie rapport I/S. Cependant, les resultats indiquent que la diagenèse induit une augmentation apparente de la preconsolidation d'un depôt de schiste argileux. Consequemment, les formations plus vieilles et plus cimentees des svhistes argileux ont apparamment une surconsolidation beaucoup plus elevee que les formations plus jeunes et non-cimentees. L' article demontre aussi que la procedure SHANSEP peut être adaptee pour estimer la resistance au cisaillement non-drainee de la plupart des schistes argileux. ZUSAMMENFASSUNG: Die Publikation prasentiert eine Analyse experimenteller Daten von verschiedenen Schiefern zuganglich in der Literatur und von mehreren Schiefern welche von NGI getesret wurden. Eine Schieferdatenbase wurde erstellt urn die Parameter zu bestimmen, welche die Festigkeit der Schiefer kontrollieren. Korrelationen zwischen der Schieferfestigkeit und Indexeigenschaften (z.B. Posositat, Alterberggrenzen), des Konsolidierverhaltnisses und des IIIit Smektit Verhaltnisses wurden hergestellt. Die Indexeigenschaften enhalten Informationen i.iber die Zusammensetzung der Schiefer, das Konsolidierverhaltnis spiegelt die Zusammendri.ickung einer Schieferlage wieder, und das Illit Smektit Verhaltnis dient als Indikator fur den Diagenesegrad. Die Festigkeit vieler Schiefer zeigt eine Korrelation mit Indexeigenschaften wie z.B. Porositat und Plasrizitatszahl. Die undrainierte Scherfestigkeit, normalisiert mit der jetzigen wirksamen in situ Spannung zeigt eine gute Korrelation mit dem Konsolidierverhaltnis, aber nicht mit dem IIIit Smektit Verhaltnis. Die Untersuchungen zeigten jedoch, dap diagenetische Effekte eine scheinbare Zunahme der Vorbelastung eines Schiefers verursachen, Als Konsequenz zeigen altere rnehr zementierte Schiefer ein scheinbares hoheres Konsolidierverhiiltnis als jungere nicht zementierte Schiefer. Die Anwendbarkeit des fur tonige Gesteine entwickelten SHANSEP Verfahrens zur Abschatzung der undrainierten Scherfestigkeit von Schiefern wird demonstriert. I INTRODUCTION Shales are fined-grained rocks that contain 50 to 100% clay-size particles and usually cleavaged parallel to the bedding plane. They are one of the most predominant materials on the uppermost layer of the earth surface and thus are of great engineering significance. Many construction specially tunnels are in shaly materials. Shales are more complicated and pose greater challenge during construction than most types of soils and rocks.
- North America > United States (0.28)
- Europe (0.28)
ABSTRACT: A series of rock shear tests was conducted on artificial sandstones of uniform and weak nature. The obtained shear strengths appeared to underestimate those by triaxial compression tests slightly in a low stress range. This marginal discrepancy was discussed based on the measured distributions of stresses and strains around the shear plane in the rock shear tests. RESUME: Des tests de cisaillement ont ete realises sur des gres artificiels uniformement friables. Les va leurs obtenues dans Ie cas du cisaillement semblent legerernent sous-estimer celles issues des tests en compression triaxiale dans une plage de faibles contraintes. Cette difference marginale fait I'objet d'une discussion basee sur la distribution des contraintes autour du plan de cisaillement au cours des tests de cisaillement. ZUSAMMENFASSUNG: An gteichformigern.: schwachem kunstlichem Sandstein wurde eine Serie von Felsscherfestigkeitsversuchen durchgefuhrt. Die erhaltenen Scherfestigkeiten waren im niedrigen Spannungsbereich gegenuber den durch dreiachsige Kompressionsversuche erhaltenen Werten erwas unterbewertet. Dieser Unterschied wird auf der Grundlage der in Felsscherfestigkeitsversuchen gemessenen Verteilungen der Spannungen und Verzerrung diskutiert. INTRODUCTION As Japan is located in the midst of seismically active areas, geotechnical investigation of foundation ground for nuclear power plants (N PPs) is considered as being of utmost importance for a successful earthquake-proof design. It has been a common practice that large-scale field tests of various kinds, including plate loading tests and rock shear tests, are conducted on the spot in exploratory adits excavated beneath the prospective sites for reactor buildings. Due to limited locations on the land suitable for future plants, Japanese power industry is now seeking possibilities of siting NPPs on offshore man-made islands. This requires new geotechnical investigation technology for foundation ground under the sea, which may preclude the use of exploratory ad its but should at least be comparable qualitatively to the cases on the land. Conceivably, characterization of offshore foundation ground should inevitably resort to conventional large-scale field tests utilizing a huge caisson, smaller-scale field tests conducted in boreholes, and laboratory tests using drilled cores. If sedimentary soft rocks have undergone no weathering and are fairly uniform, the influence of discontinuities, if any, may not be overly significant. Thus it is justified to regard rock mass behavior as not deviating too far from that predicted by a continuum model based on laboratory test data. Recent research has revealed that, pre-failure deformation of soft rock ground can be evaluated appropriately, provided that its non-linear stress ~ strain relationship is accurately characterized by carefully conducted laboratory element tests using high-quality undisturbed samples taken from the ground (Tatsuoka & Kohata, 1995). Crosschecking is recommended by field measurement of shear wave velocities for elastic moduli and also by pressuremeter tests for degraded stiffness at moderate strains. However, there still remains a question whether the same scenario holds good for strength characterization. According to the previous experiences on sedimentary soft rocks and artificial weak rocks, shear strengths evaluated by laboratory tests on small drilled cores are, in most cases, found to be higher than those by large scale field tests. This tendency is more pronounced for fine particle materials, i.e. siltstones ∼ mudstones. Field shear tests, i.e. rock shear tests, were reported to yield strengths as low as one-third to three-quarters of those by laboratory shear tests, i.e. triaxial compression tests (e.g. Miyaike et al., 1993: Sakai et al., 1990). Whereas for large particle materials, i.e. sandstones, the discrepancies were much less. In some cases, somewhat comparable strengths were obtained by both field and laboratory shear tests (e.g. Kudo et aI., 1992). For hard rocks, a well-known scale effect is taken for granted to explain different strength values obtained by tests on different specimens in size. Small rock cores are not considered as good enough to represent mechanical behavior of large rock masses. Joints and other discontinuities are attributed to be responsible for lower strengths obtained by tests of larger scales. This scale effect, however, can hardly be expected to become significant for sedimentary soft rocks, particularly for artificial weak rocks, which rarely include any kinds of local weaknesses.
- Geology > Geological Subdiscipline > Geomechanics (0.91)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.82)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.55)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.54)
ABSTRACT: Anisotropy of deformational and strength responses of four schistose rocks have been critically examined. These rocks were obtained from the foundations of two underground power house sites in the Himalayas. Specimens at different orientations (ß) varying from 0° to 900with respect to axial stress (б1) in unconfined and confined state up to 100 MPa of confining pressure were prepared and tested to evaluate the applicabilty of the non-linear criterion for prediction of triaxial compressive st rength. A methodology has been developed to predict the modulus and stress-strain curves with minimum pre-evaluation experimental data. RESUME: L'anisotropie des reponses de la resistance et de la deformation des quatre roches schisteux, ont ete attentivement examinees. Ces roches ont ere obtenus des fondations des deux centrals electriques sousrcrrains siiuees en Himalaya. Des specimens ont eres prepares et examines dans les orientations (/3) variants de 0° a 90° par rapport a la co n t ra in t e axiale (al) dans les conditions de compression sans et avec et re inte jusqu'au 100 MPa de la pression de confinement pour I'evaluation de la mise en application du cruere non -Lineair e propose et pour I'estimation de la resistance ala compression triaxiale. Une met hodotogie a ere developpec pour I'estimation de l a deformation du moc.Jule et les courbes etreinte - deformation avec un minimum de pre - evaluation des donnees exprimentales. ZUSAMMENFASSUNG: Die Reaktion von vier Schiefergesteinen wurde b ezu gl ich der Vorformung - und Festigkeitsanisotropie genau untersucht. Die betreffenden Gesteine stammen von Fundamenten weir unteschiedlichen Kraftwerke in Himalaya. Die Proben wurden mit verschiedenen Orientierungen (fJ) von DObis 900beziiglich der Axialstrcss (al) mit u nd ohne allseitiger Druck bis zu 100 MPa prepariert und gerest et, urn Anwendbarkeit von nicht-linearem kriterium von kompressiven triaxialen Festigkeit vorauszusagen. Es wurde cine Methode entwickelt, mil der das modulus und Spannung-verformung-kurve unter Anwendung der minimalen experimentellen Dalen bes rimmt wurden. I Introduction Rational and realistic approach to the analysis and design of the on ground or underground engineering structures on anisotropic rocks necessiates indepth evaluation of anisotropy in the measurment of strength (tensile and compressive) and deformation. Inherent anisotropy acquired by metamorphic rocks make them weaker and dictate its overall behaviour. Anisotropic behaviour of schists is due to the process of metamorphic differentiation (segregation of constituents). In response to high pressure and temperature gradiants associated with mountain building activities, rocks flow and recrystallize under new tectionic conditions and develop layers of contrasting mineralogical facies. Such weak foliation planes or schistosity will affect the strength and deformational responses of anisotropic rocks when orientation of stresses with respect to these weak planes changes. Prediction of the anisotropic respenses of strength and deformation of anisotropic rocks involves preparation of specimens at different orientation angles, ß (the angle between major principal stress direction and the foliation planes). The measurement of the strength anisotropy for various anisotropic rock types have been carried out by many investigators e. g. Donath (1964), Chenevert and Gatline (1965), McLamore and Gray (1967), Hoek (1968), Attewell and Sandford (1974), and Brown et al. (1977), on shales and slates, Deklotz et al. (1966), Akai et al. (1970), McCabeand Koerner (1975), Nasseri (1992), on gneisses and schists, phyllite by Ramamurthy et al, (1988), Horine and Ellicksone (1970), and Rao et. al, (1986) on sandstones, Pomeroy et al, (1971), on coal and Allirote and Boehler (1979) on diatomite. An overall analysis and review of their works exhibit that maximum failure strength is either at ß = 0° or 90° and it is minimum usually arround ß = 30°, The Shape of the curve between the uniaxial compressive strength (бc) and the orientation angle ß designated as the "type of anisotropy" and is found to be generally of three types such as "U - shape", "shoulder" and "wavey" (Fig. 1).
- Geology > Rock Type > Metamorphic Rock (0.88)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.54)
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (0.54)
ABSTRACT: A suite of thick-walled hollow cylinder tests was conducted on a smectite mudrock to investigate borehole instability mechanisms in soft rock formations during or shortly after drilling. The tests followed realistic stress paths in which external lateral stresses were maintained constant, conditions of axial plane-strain were maintained, and borehole pressure was reduced under undrained conditions until the samples yielded and collapsed. Failure was characterized by pairs of conjugate shear surfaces in between which there were large wedges of intact material. The thick-walled hollow cylinder tests on the mudrock were also modelled numerically using parameters derived from consolidated-undrained (CU) triaxial tests, assuming linear elasticity, pressure dependent elasticity and linear elasticity/plasticity, of which only the latter model yielded predictions of strengths and deformations close to the measured values. RESUME: Une serie d'essais sur cylindres creux a paroi epaisse a ete realisee à partir d'une argile smectique afin de reconnaître les causes d'instabilite des trous de forage dans les formations de roches tend res durant les sondages ou peu après, On a simule les phenomènes de pression en maintenant constantes les pressions laterales externes, en maintenant les conditions de deformation au plan axial et en reduisant la pression au trou de sondage non-draine jusqu' à ce que les echantillons cèdent et se desintègrent. La rupture etait caracterisee par des paires de surface de cisaillement entre lesquelles se trouvaient intercales des pans de materiau intacts. Les experimentations de cylindres creux à paroi epaisse en argile smectique ont ete traduites en modèles numeriques en utilisant des paramètres derives de tests triaxiaux consolides et non-draines (CU) en supposant alternativement une elasticite lineaire, une elasticite dependante de la pression, et une elasticite lineaire/plasticite; seul ce dernier modèle a permis d'obtenir des prefigurations de forces et de deformations proches des valeurs reelles mesurees. ZUSAMMENFASSUNG: Zur Erforschung von Bohrlochinstabilitat in unverfestigten Gesteinen wahrend oder kurz nach dem Bohrprozess wurden eine Reihe von Experimenten mit Hohlzylindern bestehend aus Tonstein (Smektit) durchgefuehrt. Das Spannungsverhalten in den Hohlzylindern wahrend der Experimenten folgte realistischen Bedingunen d.h. die externe, seitliche Spannung wurde konstant gehalten und der Bohrlochdruck wurde unter vollstandiger axialer Dehnungsbehinderung reduziert bis er unter undrainierten Bedingungen zur Verformung bzw. zum Bruch in den Hohlzylindern kam. Bruchverhalten wurde durch Paare von konjugierenden Scheroberflachen charakterisiert welche Keile von intakten Material begrenzten. Die hier beschriebenen Experimente mit Holyzylindern wurden ebenfalls numerisch modelliert. Die dafuer verwendeten Parameter wurden in konsolidierten-undraiierten dreiaxialen Versuchen gewonnen. Dabei wurden entweder lineare Elastizitat, druckabhangige Elastizitat oder lineare Elastizitat/ Plastizitat angenommen. Die hier gewonnen Vorhersagen bezueglich Bruchstarke und Deformationsverhalten kamen ausschließlich im letzten Modell (lineare Elastizitatl Plastizitat) den im Experiment gemessen Werten bzw. gemachten Beobachtungen nahe. 1 INTRODUCTION As a borehole is drilled, the in situ stresses and pore pressure in its vicinity are redistributed and the support previously provided by the excavated rock is partly replaced by the mud pressure. If the redistributed effective stresses exceed the load bearing capacity of the surrounding rock in compression the borehole may fail either by: 1. Hole size reduction due to large deformations and plastic flow of the rock into the borehole, without the rock losing all of its strength (e.g. mobile mudrocks and salts). 2. Hole enlargement due to brittle failure (e.g. sloughing shales and borehole breakouts). Such instabilities lead to a number of operational problems, ranging from complete or partial collapse of the well and loss of equipment, casing damage during the operational life of the well, fill on trips, poor directional control, and poor primary cementing.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.35)
ABSTRACT: The damage evolution in loaded rock is modeled on the basis of the methods of the theory of fuzzy sets. The heterogeneity of rock as well as damage are characterized by the membership functions of the rock into fuzzy sets of materials with given properties and failed materials, respectively. On the basis of developed concept of the fuzzy damage parameter, the damage evolution in heterogeneous rock is simulated. The influence of initial rock heterogeneity on its strength is studied numerically, and it is concluded that the more heterogeneous is the rock, the less its strength. RESUME: L'evolution des endommagements dans la roche heterogene est etudie. Un modele mathematique de la evolution des endommagements dans la roche, que s' etablit a la base de la theorie des ensembles flous, est elabore. L'influence de la heterogenite de la roche a la resistance limite est analyse. On montre, que plus heterogene est une roche, moins la resistance limite de la roche. ZUSAMENFASSUNG: Die Schadigungsevolution in Gestein wird mit Methoden der Theorie von Fuzzy Mengen analysiert. Das Schadigungsniveau im Gestein wird mit Fuzzy Mitgliedschaftsfunktion characterisiert. Auf Grund des entwickelten Modells des Fuzzy Schadigungsparameter, wird die Schadigungsevolution in heterogenen Gestein simuliert. Der Einfluß der anfanglichen Heterogenitat des Gesteins auf seine Festigkeit wird numerisch untersucht. Es wird gezeigt, daß mit steigender Heterogenitat des Gesteins die Festigkeit abnimmt. 1 INTRODUCTION The efficiency of rock drilling is determined by the processes of rock fragmentation to a large extent. The fragmentation of rock depends on the conditions of loading as well as on the rock properties (in particular, strength). Any data about the strength of rock are averaged and uncertain; it is a typical case, when the difference between the measured and predicted properties of rock is more than 40%, or when the strength of two specimens from the same material differ sufficiently. It is caused by the fact that rocks are usually highly heterogeneous materials, consist on different minerals and their formation during many thousands of years was determined by random processes. In order to improve the efficiency of rock fragmentation, mathematical models of this process, which describe all peculiarities of the rock destruction, are needed. Yet, only the models of single crack propagation (fracture mechanics) or the evolution of distributed microcracks (the continuum damage mechanics, see Lemaitre, 1992) can be applied efficiently to describe the rock destruction. Yet, such processes as rock crushing or cracks system evolution are of great importance in drilling (see review by Mishnaevsky Jr 1995b). For example, the energy consumption in drilling is determined by the rock crushing to a large extent; about 80 % of the loading energy is spent just for it. One of the ways to improve the efficiency of drilling is to use the interaction between large cracks under cuts (Mishnaevsky Jr 1994). So, the models of rock destruction which take into account not only single objects (like the fracture mechanics), and are applicable not only in the region up to crack formation (like the continuum damage mechanics) are needed to describe the rock fragmentation in drilling. Here, it is suggested to use the concept of the theory of fuzzy sets to model the destruction of heterogeneous rocks, and to investigate interrelations between rock strength and heterogeneity. Traditionally, the methods of the theory of fuzzy sets are applied to operate quantitatively with some linguistic, inexact or uncertain values (see Yao, 1979, Brown, 1980, etc).
ABSTRACT: 100 km of tunnels were classified with the RMR system and analyzed for rock mass strength and rock mass stability. Empirical relations between TBM penetration and utilization as a function of rock mass strength and rock mass stability are presented. RESUME: 100 km de tunnels ont ete classifie avec Ie système RMR et ont ete analyse sur resistance et stabilite de la masse rocheuse. Des relations empiriques de la penetration et de l'utilisation de machines à forer sur la base de resistance et stabilite des masses rocheuses sont presentees. ZUSAMMENFASSUNG: 100 Tunnel-km wurden nach dem RMR System klassifziert und auf Gebirgsfestigkeit und Gebirgsstabilitat untersucht. Empirische Beziehungen zwischen TBM-Penetration und Ausnutzungsgrad als Funktion von Gebirgsfestigkeit und Gebirgsstabilitat werden vorgestellt.. 1. INTRODUCTION The two basic tasks in TBM tunneling, as for any underground excavation, are (i) to excavate and remove the rock and (ii) to maintain tunnel stability until the final lining, if necessary, is installed. Application of rock engineering for TBM drives should be directed towards solving these tasks which define the TBM performance and finally the project delivery time. Performance prediction of TBM drives requires the estimation of both TBM penetration and utilization. The rate of penetration (m/h), defined as the distance mined divided by TBM operating time, depends on the TBM design (thrust, torque, disc size and spacing) as well as the rock mass properties that with stand penetration. TBM utilization is defined as the percentge of shift time during which mining occurs and depends on equipment and non-equipment downtimes (Mcfeat-Smith and Tarkoy, 1979). Maintenance of equipment and tunnel are typically scheduled on a regular basis and are mainly fixed quantities. Two major factors in estimating utilization rates are (i) the stability of the rock mass and (ii) the proper support systems as incorporated in the TBM. Figure 1 shows schematically two pairs of interactions between TBM and rock mass that influence performance data. Rock mass strength and disc thrust determine the TBM penetration while rock mass behavior often requires support installation and influences so TBM utilization. 2. METHODOLOGY The prediction of TBM penetration is typically based on extensive laboratory testing on intact rock. Uniaxial compressive strength, hardness, abrasivity and similar intact material properties have been used for this purpose. Unfortunately, very few rock masses correspond to laboratory conditions. Realistic test procedures on intact rock properties were developed at the Norwegian Institute of Technology (NIT, 1988) and the Colorado School of Mines (Ozdemir, 1995), but only the Norwegians take the effect of discontinuities on penetration into account. Generally, the presence of discontinuities increases TBM penetration. In rock engineering terms, the presence of discontinuities reduces the rock mass strength to a fraction of the intact rock strength, and for a given TBM, penetration should rather be measured against rock mass strength than against intact rock strength. Several methods to estimate the rock mass strength exist, one being the use of rock mass classifications (e.g. RMR system) and failure criterion. The RMR system (Bieniawski, 1989), which was developed for drill-and-blast (D&B) excavations, was used to quantify the rock mass quality along the TBM drives. Since the TBM excavation preserves the rock mass quality better than the D&B method, the RMR values derived from drillcores or D&B adits may be increased.
ABSTRACT: In this paper the recent sewerage and metro tunnel projects in Istanbul are summarized. A model improved as a part of NATO - TU Excavation project, that relates the cutting performance of mechanical excavators to rock mass cuttability index, is discussed with the recent data collected. The model may serve as a useful guide to contractors and machine manufacturers prior starting a tunnel project. RESUME: Dans cet expose on a resume les derniers travaux dans les tunnels d'lstanbul. On a realise ce model soutenu par Ie projet " NATO- TU Excavation" et on a defini I'index de rupture des roches en tenant compte la performance mecanique des tunneliers à I'etat de creusement. On a critique aussi ce model en prenant base les donnees obtenues durant les travaux dans les tunnels. Nous pouvons dire que ce modele sera guide aux autres participants aux creusement des tunnels. ZUSAMMENFASSUNG: Mit dieser Arbeit werden die jungsten Tunnelprojekte in Istanbul vorgestellt. lm Rahmen NATO-Excavation Project wurde ein Modell, das die Leistungen der mechanischen Vortriebsmaschinen mit Hilfe eines definierten Schneidindex fuer Gesteine feststellt, entwickelt. Das Modell wird mit den hier gesammelten Daten getestet. Es wird noch erklart, daß das hier vorgestellte Modell schon in der Planungpshase des Tunnels fuer den Zulieferer- und Tunnelbaufirmen ein Wegweiser sein wird. 1 INTRODUCTION Roadheaders have been widely used both in civil and mining industries since 1970. The main advantages are mainly; high advance rates, safety, less strata disturbances and less labor. The capital cost of these machines is very high, so if they are not selected considering rock mass properties the Consequences might be a nightmare for tunnel engineer. A contractor is always interested in predicting the machine performance prior to starting a tunnel project that will definitely define the tunnel drivage economy. The past few research works were focused on the prediction of the performance of roadheaders or TBM's from laboratory rock cutting tests. The work originated in Newcastle Upon Tyne University dealt with the correlation of in-situ data with the results of core cutting tests (Fowell and McFeat-Smith, 1976; McFeat-Smith and Fowell, 1977, 1979). In that study the specific energy obtained from small scale rock cutting test was the key factor in the machine performance prediction. A more realistic model was developed by using full scale rock cutting test results in Earth Mechanics Institute of Colorado School of Mines by Ozdemir and Rostami, et al. (1994); Ozdemir (1995). However, the work described in this paper differs from the two previously mentioned in the fact that it is based on the statistical interpretation of the field data that has been collected since 1988 from different sewerage tunnels in Istanbul (Bilgin, et al., 1988, 1990; Seyrek, et al., 1994). 2 FACTORS AFFECTING THE CUTTING PERFORMANCES OF ROADHEADERS AND IMPACT HAMMERS Factors affecting the cutting performances of mechanical excavators can be summarized as below: -Job organization and skill of machine operator affect the machine utilization time that plays an important role in determining job duration time. 3 THE GEOLOGY Paleozoic sedimentary formations from Lower Devonian to Middle Carboniferous are prevalent in the area. Many faults and geologic discontinuities developed due to Hercinian and Alpine Orogenies. The rock formation, locally named Trakya Formation is formed of fine grained, laminated, fractured and interbedded siltstone and mudstone. RQD values vary between 0 and 90%. Some diabase dykes have also been encountered while driving the tunnels and these affected progress rates as they are significantly harder than rock excavated along the major part of the tunnel routes.
- Europe (0.68)
- Asia > Middle East > Turkey > Istanbul Province > Istanbul (0.67)
ABSTRACT: A very complex failure took place at an open-pit coal mine in the eastern Turkey. The floor of the open-pit heaved up as a result of the buckling failure of the coal seam and a combined form of shear and sliding failure of slope benches occurred. The investigations showed that a weak clay band within the coal seam was the main cause of the failure. The friction angle of this band was less than 3° and dipped into the pit. with an angle of 5–7°. The failure took place while the coal seam was uncovered. In this paper, the causes of the failure are investigated through some back analyses of failure modes on the basis of geotechnical investigations, limiting equilibrium techniques and finite element analyses and the outcomes of these studies are presented and discussed. RESUME: Une rupture tress complex est. serene dans une mine de carbon à ceil overt à lest de la Turquie. Le planchcr de la mine s'est souleve à la suite du flambage d'une veine de carbon. Les terrasses en pente se sont effondrees sous une forme combinee de cisaillement et de glissement. Les recherches ont indique que la cause principale de la rupture fut la presence d'une couche d'argile situee dans la veine du carbon. Cette couche ayant un angle de frottement inferieur à 3° etait inclinee de 5° à 7° vers la pente. La rupture s'est produit lors de I'excavation de cette couche. ZUSAMMENFASSUNG: In einer offenen Grube einer Kohlenminein der Osttuerkei fand ein komplizierter Bruch statt. Der Boden der offenen Grube hob sich auf Grund eines knicken eines kohlestreifens welcher mit einer Scherung und einer Abrutschung einer treppenartigen Böschung kombiniert war. Untersuchungen haben gezeigt, dass ein weiches Tonlage die Hauptursache des Bruches war. Der Reinbungswinkel dieser Lage betrug weniger als 3° und hatte einen Einfallswinkel von 5°-7°. Der Bruch ereignete sich wahreud der Ausgrabung del' Kohlendecke. 1 INTRODUCTlON A very complex failure took place at the Kişlaköy open-pit mine of Afşin-Elbistan Lignite Mining Complex in the Eastern Turkey in 1984. The pit-floor heaved up as a result of the buckling failure of the lignite seam and a combined form of shear and sliding failure of mining benches occurred. The investigations showed that weak clay layers existed in the lignite seam of about. 20 m thick and one of these clay layers played an important role in the failure. The friction angle of this layer was about 3° and dipped into the pit with an angle of 6° (Ulusay et al. 1986). The main failure occurred on July 1, 1984 at the North-West slope of the kişlaköy open-pit. (Polat and Yueksel 1984). The failure involved a region, which was 650 m long and 250 wide (Fig. 1). The length of the region was later extended to 1000 m with subsequent failures. The final horizontal movement of the failed slope was more than 50 metres. The lignite seam of the pit-floor was heaved up and it had a set of buckles whose strikes were almost perpendicular to direction of movement and parallel to the axis of benches (Fig.2). Fig. 3 shows three-cross sections of the failed slope.
- Materials > Metals & Mining > Coal (1.00)
- Energy (1.00)
The Mechanical And Hydraulic Characteristics of Granite And Gneiss Under Temperature Variation
Lee, Hee Suk (Seoul National University) | Lee, Hi-Keun (Seoul National University) | Park, Yeon-Jun (Korea Institute of Geology, Mining & Materials) | Kwon, Kwang-Soo (Korea Institute of Geology, Mining & Materials)
ABSTRACT: Most underground engineering projects, including the safe disposal of radioactive wastes, geothermal energy production, underground oil storage and heat storage in rock cavern, require knowledge of the mechanical, thermal, hydraulic characteristics of rockmass. This paper describes the results of various tests conducted on Whangdeung granite and Gyounggyi gneiss to understand the mechanical behaviors of rock under temperature variation. The effect of the anisotropy caused by the rift and foliation of the rocks, and the hydraulic characteristics of the rocks and artificially fractured joints were also studied at different temperatures. The results could be used in the design of various underground facilities. RESUME: Le depot sûr des dechets radioactifs, la production de I'energie geothermale, Ie stockage du petrole brut et Ie stockage thermique dans la caveme rocheuse ont besoin de la connaissance sur la caractesristique mecanique, thermale et hydraulique du massif rocheux provoquee par la source thermale. Dans cet article, plusieurs essais ont ete realises pour comprendre Ie comportement mecanique du granite provenant de Whangdeung et du gneiss de Gyounggyi en fonction de la variation de temperaure en tenant compte du lit et de la schistosite, En outre, les essais de permeabilite ont ete effectues sur Ie granite fissure artificiellement en vue d'examiner Ie changement de la permeabilite et des caracteristiques de I'ecoulement du fluide en fonction de la temperature et de la contrainte dans les roches fissurees. ZUSSAMENFASSUNG: Die zuverlassige Einrichtung von radioactiven Abfalle, die Produktion der geothermischen Energie, die Untergrundsablagerung des ÖI, und die Warmelagerung in Gesteinshöhle benötigen die Informatione von der mechanishen, thermischen, hydraulishe Eigenschaften von Gescheinsmasse, die von thermische Quelle verursacht wurden. In dieser Abhandlung, verschiedene Experimente untergenommen, um das mechanischen Verhalten von Gesteine, Whangdeung Granit und Gyunggyi Geiss, unter Änderung Konditionen der Temperatur, jenach the the Geriß und Foliationsorientation. Überdies, die Permeabilitat ist in dem konstlich gerißenen Granit gemessen, um die Characteristika des fluessigen Strömen unter andemden Temperatur in Gesteinsriß festzustellen. 1. INTRODUCTION Most underground engineering projects, including the safe disposal of radioactive wastes, geothermal energy production, underground oil storage and heat storage in rock cavern, require knowledge of the mechanical, thermal, hydraulic characteristics of rockmass, Many authors have been conducting the study on thermo-mechanical behavior of rock. According to the studies of Henze, Lee, and Lau et. aI., it is reported that compressive strength of rocks generally decreases with increasing temperature, while it increases with increasing confining pressure. Also, the effect of temperature on the tensile strength of rocks seems much more significant than compressive strength. Heuze(1983) reported that Poisson's ratio, cohesion, and internal friction angle also decreased with increasing temperatures. However, it is known that thermo-mechanical behaviors of crystalline rocks are considerably dependent on the rock type, composition of rock-forming minerals, texture condition, arrangements of grains and stratified shape etc. Thus, it is necessary to identify the characteristics of rocks through various tests meeting the purpose of performance. Permeability of the crystalline rocks are generally considered as 10–7 darcys or less, practically regarded as impermeable media Most of transport phenomena of fluid in rockmass take place througth the discontinuities in rockmass, thus understanding of the fluid transport characteristics in discontinuous rockmass is critical to ensure the stability of the underground facilities. In Korea, thermo-mechanical studies on rocks are rather new and only a few papers could be found. Studies on thermal cracking and changes in properties with varing temperature were conducted by Lee(1993) for Granite and Granodiorite, but failed to measure the lateral strain in the triaxial cell and thus could not identify the change in deformability of rocks. Yoon(l992) measured the permeability of rocks and manufactured joints at room temperature only. This paper describes the results of various tests conducted on Whangdeung granite and Gyounggyi gneiss to understand the mechanical behaviors of rock under temperature variation. The effect of the anisotropy caused by the rift and foliation of the rocks, and the hydraulic characteristics of the rocks and artificially fractured joints were also studied at different temperatures. The results could be used in the design of various underground facilities.
- Geology > Rock Type > Metamorphic Rock > Gneiss (1.00)
- Geology > Rock Type > Igneous Rock > Granite (1.00)