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This study was carried out in a bid to survey Ganboke gold mine in Pala, Mayo-Kebbi Province, southwestern Chad. The Ganboke mine is now being prepared for investigation and development, and the research sought to perform rock properties tests of relevant rocks through its geological survey, rock mass evaluation, and in-situ and laboratory tests and analyze the stability by the means of limit equilibrium method, thereby suggest appropriate methods to design the pit slope and individual benches in Ganboke mine. Targenting GS1-GS1' section with the depth of 180 m and GS2-GS2' section with the depth of 150 m in the survey area, we set the height of the bench at 10 m and 15 m, and the angle of bench at 60 and 70, respectively, and then reviewed the stability for dried condition and saturated condition. The result of examination indicated that it would be appropriate to set the bench height at 10m and the bench angle at 60 in developing the mine slopes concerned. Cette etude est realise dans le but de faire des recherches sur Ganboke mine d'or dans Pala, Mayo- Kebbi Provence, Tchad sud-ouest. La Ganboke mine est actuellement en train de etre dispose à la investigation et le developpement, et la recherche a cherche à accomplir les tests de la proprietè des roches par l'intermediaire de la etude geologique, la evaluation de la masse rocheuse, et in-situ et les tests de laboratoire et à faire l'analyse de la stabilite au moyen de la methode d'equilibre limite, de ce fait à proposer le methodes propres à faire le plan de la pente et les gradins individuels dans la Ganboke mine. Concernant la section de GS1-GS1' avec la profondeur de 180 m et la section de GS2- GS2' avec la profondeur de 150 m dans l'aire d'etude, nous mîmes l'hauteur du gradin à 10 m et 15 m, et l'angle du gradin à 60 and 70, respectivement, et alors nous avon reconsidere la stabilite pour la condition sèche et la condition sature. Le resultat d'examen a indique que il pourrait être propre de mettre l'hauteur du gradin à 10m et l'angle du gradin à 60 en developpant les pentes de la mine concerne. Diese Forschung wurde um das Gold Bergwerk zu ueberschauen in Pala, Mayo-Kebbi Provinz, der Suedwesten Chad ausgefuehren. Das Ganboke Bergwerk ist jetzt zur Erforschung und Entwicklung vorgebereiten worden, und die Forschung suchte zu ausfuehren die Pruefungen der Felseigenschaft durch geologischen Überblick, Felsmassewertbestimmung, und In-situ und Lavorversuch auf, und analysieren die Stabilitat mittelst der Grenzegleichgewichtsmethode, da-durch schlug die angemes-sen Methoden zu entwerfen die Böschungen und die einzelnen Banke im Ganboke Bergwerk vor. Fuer den Abschnitt GS1-GS1' mit der Tiefe von 180 m und GS2-GS2' mit der Tiefe von 150 m in der Überblickflache, wir setzten die Bankhöhe an 10 m und 15 m, und das Bankwinkel an 60 und 70, beziehungsweise, und dann zurueckblickten die Stabilitat fuer die getrockneten Bedingungen und die gesattigten Bedingungen. Das Ergebnis der Untersuchung anzeigte daß es wuerde angemessen sein zu setzen die Bqnkhöhe an 10m und das Bankwinkel an 60 in der Entwickelungen vom Bergwerk beteiligt. Introduction The survey area, located in Mayo-Kebbi Province, southwestern Chad, belongs to Pala (Fig. 1). Pala is located about 125 km of Lere neighboring the eastern border of Cameroon, in the eastern inland of Chad. The survey area was named Ganboke south after the village. The geology of this area is mainly composed of the Precambrian greenstone belt which is characterized by abundant greenstone, batholith of Mayo-Kebbi, plutons of alkali granite and charnockite, hypabyssal and ultrabasic rocks, Mesozoic sedimentary rocks of Lame series, Cenozoic lat-erite and paleochadian formation of sand, clay, gravel, and sandstone. The Ganboke mine is now being prepared for survey and development, and it is designed by open pit mining because of plain surface and massive ore body. With open pits, it is important, among others, to determine the heights of benches and overall slopes, and slopes angles. The research sought to conduct geological surveys, rock mass evaluation, in-situ and laboratory experiments, define rocks properties and analyze the stability, and determine the inclination of benches and overall slope within the pits, thereby suggesting methods to design the pit slope and individual benches appropriate for mining works in developing the mines.
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Native Element Mineral > Gold (0.63)
The paper is devoted to two major aspects related to the abandonment of salt mines:Long-term risk associated with the mechanical instability of surface and its consequences for public security and properties. Long term dissolution and transport of salt resulting from its communication with groundwater. Basic characteristic features of salt deposits and mining methods are presented through the studies already undertaken on French mines. This analysis allows to identify major hazards encountered in different traditional salt mines and solution-mining cavities. In particular, the role of overburden (presence and thickness of salt layer in exploitation roof, presence of clayey rocks or hard rocks e.g. dolomite or anhydrite), presence of water-bearing strata and possibly natural brine levels, discontinuities, etc. are discussed. In the second part, the main features of mechanical behaviour of salt (creep, damage) as well as transfer processes of this material are presented. The influence of these aspects on the long term evolution of abandoned salt mines is then analysed. ZUSAMMENFASSUNG Der Artikel bezieht sich auf zwei bedeutende Aspekte beim Salzabbau:Das langsfristige Risiko zur Bodenoberflacheunbestandigkeit und sein Einfluss ueber Mensch= und Guetersicherheit. Die langsfristige Auflösung und Beförderung des Salz beruhen sich auf Studien ueber französiche Bergbauen. Diese Analyse emöglicht es, die bedeutendesten Risiken in verschiedenen Salzgruben zu identifizieren, bzw. Traditionellen oder durch Auflösung abgebauten. Insbesondere wird die Rolle des Deckgebirges (Vorhandensein und Dicke von Salzschicht am Dach des Grube, Beisein von Tanlager oder hartem Gestein wie Bitterkalk oder Anhydrid), Beisein von wasserhaltigem Boden und/oder gesalzenen Wasserflachen, Trennflachen, usw… erötert. Im zweiten Teil werden die haupsachlichen Eigenschaften des Salzverhaltens (Kriechen und Beschadigung) beschrieben. Ihr Einfluss ueber das Verhalten von stillgelegten Bergwerken lasst sich analysieren. SCHLÜSSELWÖRTER Bergwerksbetrieb, Stilllegung, Mechanik, Bestandigkeit, Ausbreitung, Aussolung, Solewasser. RESUME L'article est consacre à deux aspects majeurs lies à l'abandon d'exploitations de sel:Le risque d'une instabilite à long terme de la surface du sol et son incidence sur la securite des personnes et des biens. La dissolution à long terme et le transport de sel sous l'effet d'une communication avec des eaux souterraines. Les principales caracteristiques de gisements et d'exploitations de sel sont presentees en s'appuyant sur les etudes anterieures realisees sur les exploitations en France. Cette analyse permet d'identifier les risques majeurs rencontres dans differentes mines de sel traditionnelles ou exploitees par dissolution. En particulier, le rôle du recouvrement (presence et epaisseur d'un banc de sel au toit de l'exploitation, presence de terrains argileux ou de roches dures telles que la dolomie ou de l'anhydrite), presence de terrains aquifères ou de nappes salees eventuelles, discontinuites, etc. sont discutees. Dans la deuxième partie, les principaux traits du comportement mecanique du sel (fluage, endommagement) ainsi que les processus de transport de ce materiau sont presentes. L'influence de ces aspects sur le comportement à long terme d'exploitations abandonnees de sel est ensuite analysee. MOTS CLES: exploitation, abandon, mecanique, sel, stabilite, transport, dissolution, saumure. Introduction After a period of intense exploitation of salt over the past, especially during the two latest centuries.
- Geology > Rock Type > Sedimentary Rock (1.00)
- Geology > Mineral > Halide > Halite (1.00)
- Geology > Geological Subdiscipline > Geomechanics (0.96)
The assessment of overall modulus (or stiffness) of a fractured weak to moderately strong rock mass is a key parameter in the design of civil engineering works in these materials. It also provides the highest level of uncertainty due to scale effects, anisotropy and the influence of joint frequency and joint stiffness. Using the example of the Melbourne Mudstone, this paper compares approaches using empirical rules based on intact rock strength, laboratory testing, insitu field testing, semi-quantitative assessment techniques based on rock mass classification and back analyses. L'evaluation du module (ou rigidite) global d'une masse rocheuse faible et fissuree a moderement forte est un paramètre principal dans la conception des travaux du genie civil dans ces types de materiaux. Elle fournit egalement le niveau le plus eleve d'incertitude due aux effets d'echelle, à l'anisotropie et à l'influence de la frequence et de la rigidite des joints rocheux. En utilisant l'exemple du schiste de Melbourne, cet article compare des approches empiriques basees sur la force intacte de La roche, les essais experimentaux au laboratoire, les essais sur site, les techniques semi-quantitatives d'evaluation basees sur la classification de la masse rocheuse et les analyses en retour. Die Schaetzung des allgemeinen Steifigkeit-Moduls des gebrochenen schwachen bis zu maessig starken Felsmassen ist eine Haupt- Annahme in dem Entwurf von Tiefbau-Projekten in diesen Materialien. Es verursacht den hoechsten Grad der Ungewissheit in Folge der Groessenordnung, Spaltorientierung und dem Einfluss der Haeufigkeit der Risse und Bruch-Steife. Unter Verwendung des Beispiels des Melbourner Tonsteine, vergleicht diese Darlegung die Anwendung der empirischen Regeln, die sich auf die Staerke des ungestoerten Fels Basieren mit Versuchen in der Material Pruefungsanstalt, Untersuchungen auf der Baustelle und halb-quantitative Schaetzungsverfahren, die sich auf die Felsmassen Klassifikation und fruehere Analysen stuetzen. Introduction The assessment of overall modulus (or stiffness) of a fractured weak to moderately strong rock mass is a key parameter in the design of civil engineering works in these materials. It also provides the highest level of uncertainty due to scale effects, anisotropy and the influence of joint frequency and joint stiffness. Rock mass properties are difficult to measure directly and their estimation has historically relied on subjective assessments of rock mass quality and measurements of intact values. Using the example of the Melbourne Mudstone, this paper compares approaches using empirical rules based on intact rock strength, laboratory testing, insitu field testing, semi-quantitative assessment techniques based on rock mass classification and back analyses. ‘Melbourne Mudstone’ is a generic name used to describe the open folded and faulted sedimentary deposits comprising predominantly siltstones with some fine grained sandstones and rare mudstones of Silurian and early Devonian age that underlie the Melbourne area. The weathering state, varying from extremely weathered to fresh, was first classified for engineering purposes by Bamford (1969) and Nielson (1970). The saturated water content of the siltstone provides a useful quantitative indicator of the engineering properties of the intact rock varying from around 20% (void ratio ≈ 0.54).
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
ABSTRACT An experimental programme for damage assessment was performed in the vicinity of the main shaft of Andra's Underground Research Laboratory, currently under construction in the East of France, when the shaft is crossing the Kimmeridgian marls between 80 and 100 m depth. The mechanical behaviour was analysed by mean of convergence and displacement measurements. The disturbance into the wall was assessed using numerous methods such as measurement of sonic velocities, permeability measurement and VSP measurement in radial boreholes. The intensity of the damaged zone is low, and its extension does not exceed 0.5 time the radius of the shaft. It does not seem to depend on blasting patterns. ZUSAMMENFASSUNG Ein Forschungs- und Versuchsprogramm wurde aufgestellt, um die beschadigte Zone im Bereich der Kimmeridgemergel zwischen 80 und 100 Meter Tiefe beim Zugangsschacht des im Bau befindlichen Andralabors im Osten Frankreichs zu berechnen. Das mechanische Verhalten der Formationen wird auf der Grundlage von Konvergenz- und Verschiebungsmessungen ermittelt. Verschiedene Messmethoden, wie z.B. mikroseismische Geschwindigkeite Messungen, Permeabilitas- und Beschleunigungsbestimmungen in strahlenförmigen Bohranordnungen, erlaubten die Ermittlung des Beschadigungscharakters der Schachtwand. Die Intensitat der beschadigten Zone ist niedrig, ihre Ausdehnung uebersteigt nicht die Halfte des Radius des Zugangsstollens und scheint unabhangig vom Schema der Sprengstoffanordnungen zu sein. RESUME Un programme experimental visant à evaluer la zone endommagee autour du puits d'accès du Laboratoire de Recherche Souterrain de l'Andra actuellement en construction dans l'Est de la France a ete mis en oeuvre lors de la traversee des marnes du Kimmeridgien entre 80 et 100 m de profondeur. Le comportement mecanique des formations est evalue à partir de mesures de convergence et de deplacements. La mise en oeuvre de nombreuses methodes, telles que des mesures microsismiques, des mesures de permeabilite et d'accelerometrie en forages radiaux, a permis de caracteriser l'endommagement en paroi du puits. L'intensite de la zone endommagee est faible et son extension ne depasse pas 0,5 fois le rayon du puits. L'endommagement semble independant des schemas de tirs testes. Introduction and objectives Andra (Agence Nationale pour la gestion des Dechets RAdioactifs) is managing an experimental programme in France to study the feasability of radioactive waste disposal in deep argillitic rock formation (claystone). An Underground Research Laboratory (URL) is currently being constructed at Bure (Meuse/Haute-Marne) in the East part of Paris Basin to investigate the Callovo-Oxfordian argillitic formation located at a depth of about 420–510 m (Piguet, 2001). Before reaching the target argillitic formation, the two vertical shafts, currently under construction, cross a sequence of Kimmeridgian marls interlayed with calcareous beds (up to 120 m depth) and then the Oxfordian calcareous formations. The performance assessment of a disposal has to take into consideration the disturbance due to excavation and particularly the extension of the microcracked zone behind the excavation's wall, as well as its intensity. This so called EDZ (Excavation Damaged Zone) could be associated with a locally increased permeability and represents a risk that radioelements could leak from an eventual disposal to the biosphere. This point has to be carefully controlled and the influence of the excavation method has to be appreciated.
- Geology > Rock Type (0.34)
- Geology > Geological Subdiscipline > Geomechanics (0.31)
- Reservoir Description and Dynamics > Reservoir Characterization > Near-well and vertical seismic profiles (0.90)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.72)
- Health, Safety, Environment & Sustainability > Environment > Waste management (0.54)
ABSTRACT The Urft dam, the Diemel dam and the Eder dam are three old masonry dams located in Germany. The paper describes the rehabilitation measures and the corresponding stability analyses carried out to adjust the dams to today's standards. Remedial works such as the excavation of inspection galleries, the installation of a grout curtain with a downstream drainage screen as well as the installation of pre-stressed permanent tendons were carried out. In all three cases the stability of the upgraded dam could be proven on the basis of finite element analyses. ZUSAMMENFASSUNG Die Urft-, Diemel- und Edertalsperre sind drei alte deutsche Schwergewichtsmauern aus Bruchsteinmauerwerk. Im Beitrag werden Instandsetzungsmaß- nahmen und Standsicherheitsnachweise beschrieben, die erforderlich waren, um die Staumauern an den heutigen Stand der Technik anzupassen. Hierzu wurden Kontrollgange aufgefahren, Dichtungsschleier mit luftseitiger Dranage sowie vorgespannte Daueranker hergestellt. In allen drei Fallen konnte unter Beruecksichtigung der Instandsetzungsmaßnahmen die Standsicherheit der Mauer auf der Grundlage von Berechnungen nach der Methode der finiten Elemente nachgewiesen werden. RÉSUMÉ Les barrages de Urft, Diemel et Eder sont trois barrages-poids vieux allemands construit de maçonnerie de moellon. Dans cet article, operations de remise en etat et preuves de stabilite sont decrits, qui etaient necessaires pour adapter les barrages à l'etat de la technique actuelle. À cet effet, des galeries de contrôle etaient creuses, voiles d'etancheite avec des drains à la face aval et tirants precontraints permanents etaient fabriques. Dans tous les trois cas, tenant compte des operations de remise en etat, la stabilite de la barrage pouvait être prouvee à partir de calculs selon la methode des elements finis. Introduction The stability of the Urft dam, which was built from 1900 until 1905, as well as the Diemel dam and the Eder dam, which were built between 1908 and 1923, was not sufficient under consideration of today's standards. Therefore, rehabilitation measures became necessary. Urft dam Dam and foundation rock The Urft dam has a height of 58 m and a width at the foundation level of approximately 50.5 m. The 226-metrelong dam crest has a curvature with a radius of 200 m. The Urft reservoir has a storage volume of approximately 45 million m (Fig. 1). The rock mass in the area of the dam belongs to the Upper Rurberger layers of the Lower Devonian. There are massive sandstone layers as well as alternating sequences of silt-, sand- and claystone layers at the left slope, whereas silt- and claystones are prevailing in the middle of the valley. The right hillside mostly consists of alternating sequences of silt- and sandstone layers. The orientation of the families of discontinuities, which are important for the stability and the permeability of the underlying rock, are shown in Figure 2. (Figure in full paper) Monitoring program and results In order to adjust the dam to the generally acknowledged technical standards, an appropriate remediation program was developed. Most important elements of the rehabilitation measures were the excavation of two inspection galleries by blasting and the installation of a monitoring program.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.45)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.45)
The 1,000 MW Hydro Power Station Masjed-e-Soleiman (formerly called Godar-e-Landar) in Iran is under construction since 1992. The rock engineering aspects of the major underground structure, i.e. the powerhouse cavern shall be reported on in detail. The geotechnical investigations are described and results given. The results of several geotechnical analyses are presented. The designed and executed rock support is given. A description of the monitoring systems and typical measurement results obtained during and after excavation are presented. The lessons learnt during construction of the Stage-I powerhouse cavern were applied on the extension of the powerhouse cavern, which is to house an additional 1000 MW. Details regarding the unexpected behaviour of the Mudstones are given. Die 1000 MW Wasserkraftanlage Masjed-e-Soleiman (vormals Godar-e-Landar genannt) befindet sich seit 1992 in Bau. Dieser Artikel berichtet im Detail ueber die felsbaulichen Aspekte der Untertagebauwerke, insb. der Maschinenkaverne. Die geotechnischen Untersuchungen werden beschrieben und deren Ergebnisse wie die Ergebnisse verschiedener Berechnungen werden prasentiert. Die geplante und die ausgefuehrte Felssicherung wird angegeben. Die eingebauten Überwachungseinrichtungen werden beschrieben und typische Ergebnisse wahrend des Aushubs und danach werden dargestellt. Die Erfahrungen beim Aushub der Kaverne der Stufe I wurden beim Entwurf der Kaverne der Erweiterungsstufe II, die weitere 1000 MW beherbergen wird, beruecksichtigt. Details zum unerwarteten Verhalten des Schluff-/Tonsteins werden angegeben. La centrale hydroelectrique de Masjed-e-Soleiman (denommee anciennement Godar-e-Landar), d'une puissance de 1.000 MW, est en construction depuis 1992. Un rapport detaille sera presente sur les aspects relatifs à la construction en enrochements de l'amenagement souterrain principal, à savoir la caverne abritant la salle des machines. Une description des investigations geotechniques realisees y est fournie ainsi que les resultats correspondants. En outre sont presentes les resultats de plusieurs analyses geotechniques. L'ancrage dans la roche tel que projete et realise est presente. Une description des systèmes de contrôle ainsi que les resultats de mesures typiques obtenus au cours des travaux d'excavation sont donnes. Les leçons tirees lors de la construction de la Phase 1 de la caverne de la salle des machines furent appliquees à l'extension de la caverne de la salle des machines, qui doit abriter une unite supplementaire d'une puissance de 1.000 MW. Par ailleurs, des details sont donnes sur le comportement inattendu des argilites. Introduction The hydropower project Masjed-e-Soleiman owned by the Iran Water & Power Authority is situated on the Karun river and is under construction since 1994. The project is executed in two stages. Lahmeyer International was part of a Joint Venture during Tender Design and Construction supervision for Stage-I of the project. For the Extension of the project Lahmeyer took on the role of technical adviser to the Engineer. The project consists of the following main components:clay core rockfill dam of 165m height powerhouse cavern 30m*50m*151m (span, height, length) plus extension of another 112 m length with a total installed capacity of 2000MW trafo cavern 15m*23m*114m (span, height, length) plus extension two headrace tunnels/pressure shafts for each stage with 10.5m excavation diameter two tailrace tunnels for each stage with 12.5m excavation diameter main access tunnel and a separate access tunnel to the PHC-Extension both with 8m excavation diameter two diversion tunnels (one of which will function as a bottom outlet) with 11m excavation diameter. Construction of the diversion tunnels started in June 1992 and in September 1995 the river was diverted.
- Geology > Mineral > Silicate > Phyllosilicate (1.00)
- Geology > Geological Subdiscipline (0.94)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.73)
- Energy > Renewable > Hydroelectric (0.88)
- Energy > Power Industry (0.54)
- Well Drilling (0.69)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.47)
- Management > Professionalism, Training, and Education > Communities of practice (0.34)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.34)
The Hoek-Brown failure criterion is often applied to a wider range of rocks than the isotropic rock masses to which it is strictly applicable. This paper evaluates the patterns of defects in rock masses using spherical projection contour plots of samples of randomly-generated orientations and datasets from mapping of New Zealand closely-jointed greywacke rock masses. Two indices from the contour plots - the area within the 1% contour (A1% ) and maximum concentration (Cmax) are introduced for distinguishing uniform (isotropic), random or regular defect patterns. The indices provide a potential extension to current guidelines on the use of the Hoek-Brown failure criterion. The paper also outlines kinematic checks to assess the influence of defect clusters on rock mass strength. Das Hoek-Brown Bruchkriterium, das strikte nur fuer isotrope Gefuege gilt, findet oft einen viel weiteren Anwendungsbereich. Diese Arbeit bewertet diverse Dispersionsmuster der Defekte einer Gesteinsmasse. Wir vergleichen in sphaerischer ProjektionBeispiele zufaelliger Orientierung von Defekten und Felddaten ueber neuseelaendisache engstaendig geklueftete Grauwacken. Die Projektionen werden durch die Indices A1% (Flaechenanteil des 1% -Bereichs) and Cmax (Hoechstkonzentration) gekennzeichnet, welche isotrope, zufaellige und regulaere Muster unterscheiden und die aktuellen Richtlinien zum Hoek-Brown Kriterium ergaenzen. Wir testen ferner Defektgruppen der Gesteine kinematisch auf ihren Einfluss auf Massenfestigkeit. Le critère de rupture de Hoek-Brown est souvent utilise sur une variete de roches plus etendue que les masses rocheuses auxquelles il est strictement applicable. Ce travail evalue la distribution des defauts au sein d'une masse rocheuse en utilisant une projection spherique des contours d'echantillons d'orientations generees aleatoirement et de donnees de cartographie provenant de greywackes à joints rapproches de Nouvelle Zelande. Deux indices de cette projection - la zone des contours en dessous de 1 % (A1% ) et celle de concentration maximum (Cmax) sont introduites pour distinguer les repartitions uniformes (isotropes), aleatoires ou regulières. Ces indices fournissent une extension potentielle aux règles d'utilisation du critère de rupture de Hoek-Brown. Ce travail utilisent egalement les contrôles cinematiques pour evaluer l'influence des groupes de defauts sur la resistance de la masse rocheuse. Introduction Rock defect patterns are an important attribute in rock mass strength. The Hoek-Brown failure criterion 1 is the commonly used method for assessing the strength of jointed rocks. Critical assumptions for the criterion are that the rock and the rock mass behaviour are isotropic and that the criterion should only be applied to those rock masses in which there are a sufficient number of closely spaced discontinuities that isotropic behaviour involving failure on discontinuities can be assumed. Despite this clear warning about the limitation of the failure criterion, the procedure is often used fairly indiscriminately to assess the strength of rock masses with well ordered defect patterns. Upper Paleozoic to Mesozoic-age greywacke rocks are widespread throughout New Zealand and these basement rocks form the foundations for many of the country's engineering projects. The rocks are commonly closely-jointed as a result of their complex tectonic and geological history.
ABSTRACT This paper contributes to the study of underground structures in argillaceous media, especially Tournemire argillites (Aveyron, France). The basic results obtained over six years in two experimental drifts at the Tournemire site are presented. In situ measurements cover drift wall temperature, humidity and convergence. Delayed convergence represents around 50–65% of the total measured convergence. Analysis of the measurements has shown that delayed convergence is explained by the viscoplastic behaviour of the argillaceous formations. Lemaitre's rheological model has been extended to the orthotropic case, as Tournemire argillite is naturally anisotropic. The triaxial creep test results on samples at different orientations enabled the parameters of the Tournemire argillite to be identified in terms of orthotropic viscoplastic law. A plane deformation model, using this rheological law and the initial stress field in the site, was developed to interpret the convergence measurements in the drifts. The computed results match the measurements well, especially during the excavation phase. ZUSAMMENFASSUNG Der vorliegende Artikel ist ein Beitrag zur Untersuchung der unterirdischen Strukturen tonhaltiger Milieus, insbesondere der Tongesteine von Tournemire (Aveyron, Frankreich). Die wichtigsten Ergebnisse, die in zwei Forschungsstrecken am Standort Tournemine ueber einen Beobachtungszeitraum von sechs Jahren zusammengetragen wurden, werden hier vorgestellt. Gemessen wurden in situ Temperatur, Feuchtigkeit und Streckenkonvergenz. Von der insgesamt gemessenen Konvergenz sind etwa 50 bis 65 % auf zeitlich verzögerte Konvergenz zurueckzufuehren. Die Auswertung aller Messungen hat ergeben, dass die zeitverzögerte Konvergenz mit dem viskos-plastischen Verhalten des Tonsteinmassivs zu erklaren ist. Aufgrund der naturgemaßen Anisotropie des Tongesteins von Tournemine wurde das rheologische Modell von Lemaitre auf den orthotropen Fall ausgedehnt. Triaxiale Kriechversuche bei jeweils unterschiedlicher Ausrichtung dienten der Ermittlung der einzelnen Parameter des orthotropen, viskos-plastischen Gesetzes. Zur Auswertung der Konvergenzmessungen innerhalb der beiden Strecken wurde unter Beachtung dieses rheologischen Modells sowie des urspruenglichen Spannungszustands vor Ort ein flachiges Deformationsmodell entwickelt. Die Rechenergebnisse zeigen eine gute Übereinstimmung mit den Messungen, insbesondere wahrend der Vortriebsphase. RESUME Cet article est une contribution à l'etude des structures souterraines dans les milieux argileux, notamment les argilites de Tournemire (Aveyron, France). Les principaux resultats obtenus pendant six annees, dans deux galeries d'experimentation au site de Tournemire, sont presentes. Ces mesures portent sur la temperature, l'humidite et la convergence des parements des galeries. La convergence differee represente environ 50 à 65% de la convergence totale mesuree. L'analyse de l'ensemble des mesures a montre que la convergence differee est interpretee par le comportement viscoplastique du massif argileux. Etant donne que l'argilite de Tournemire est naturellement anisotrope, le modèle rheologique de Lemaitre a ete etendu au cas orthotrope. Les resultats des essais de fluage triaxial, sur des echantillons à differentes orientations, ont permis de determiner les paramètres de la loi viscoplastique orthotrope. Un modèle en deformation plane, utilisant cette loi rheologique et l'etat de contrainte initiale dans le site, a ete developpe en vue d'interpreter les mesures de convergence dans les galeries. Les resultats des calculs sont en bon accord avec les mesures et plus particulièrement durant la phase de creusement. 1. Introduction Deep geological disposal of high-level radioactive waste poses earth science experts the specific problem of how to manage the very long radionuclide containment period. Burying this waste represents a large-scale, protracted activity. The timescales considered are of the order of magnitude of 10 years, which considerably exceeds the lifetime of the earliest engineered structures. There are several ways of overcoming the difficulty of extrapolating to large timescales, such as studying observable phenomena in the laboratory at moderate or even low speeds, studying natural equivalents, and studying early structures such as the Tournemire tunnel, which was excavated a hundred years ago. The existence of the old tunnel and two more recent drifts on this site, excavated six years ago, provides the opportunity to study the behaviour of underground-engineered structures on two different timescales. At the Tournemire site, the old railway tunnel, 1885 m long, provides direct access to a 250-metre thick argillaceous layer, which IRSN (the Institute for Radiological Protection and Nuclear Safety) is using for many different experiments. The site is a simple monoclinal structure composed, on a large scale, of three large layers: a lower limestone and dolomitic layer, about 300 m thick.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.91)
SUMMARY Geotechnical problems often lead to an increase of construction time and costs for large highway and railway projects. Some reasons, which have led to failures and thus to a delay of construction works as well as to increasing costs, are demonstrated by means of case histories, in which the author was involved as expert or planner. Proposals are made how to identify the reasons and to avoid repetitions. ZUSAMMENFASSUNG Bei Großprojekten der Verkehrsinfrastruktur stehen haufig geotechnische Aufgabenstellungen im Vordergrund. Wegen geotechnischer Probleme kam und kommt es haufig zu Termin- und Kostenueberschreitungen. Anhand einiger Beispiele, bei denen der Autor als Gutachter und Planer beteiligt war, wird gezeigt, welche Ursachen zu Schadensfallen und damit auch zu Termin- und Kostenueberschreitungen gefuehrt haben. Es werden Hinweise und Anregungen gegeben, wie die Ursachen erkannt und Wiederholungen von Schadensfallen vermieden werden können. RÉSUMÉ À grands projets de l'infrastructure de la circulation, souvent des taches geotechniques sont au premier plan. Par suite de problèmes geotechniques, souvent des dates et frais ont ete depasses. Au moyen de quelques exemples, à lesquels l'auteur participait comme expert et planificateur, les causes sont mises en vue qui menaient à des cas de dommage et par cela aussi à des depassements de dates et frais. Des indications et suggestions sont donnees pour s'apercevoir des causes et eviter des repetitions de cas de dommages. Introduction The author has participated in many large-scale transportation infrastructure projects in Germany and abroad. Many of these projects are located in subdued mountain ranges. Rock mechanical and geological problems are therefore in the forefront. In the following paper some examples are illustrated in which deadlines and budget limits were exceeded due to geotechnical questions. The purpose of this paper is to draw attention to this problem and to put the discussion on risk analysis and risk management on a broader basis. Incorrect assessments which have led to cases of damage and thus to deadlines and budget limits being exceeded have hurt the trust of the clients into our professional segment. It is therefore important in my opinion to identify the causes in order to avoid recurrence. Slopes and construction pits Herdecke slope failure During excavation works for the construction of the bypass of the city of Herdecke, Germany, in the eighties, a slope failure occurred after strong rainfall (Fig. 1). About 300.000 m of rock slid on bedding planes of an alternating series of Devonian sand- and siltstones. The bedding planes were filled with mixed-grained soils. Apart from extensive damage to two residential buildings located on the slope, the sliding masses represented a threat to a Herdecke city district located at the slope toe, because a surcharge fill placed at short notice at the base of the slide did not lead to a stabilization of the slope [1]. On the contrary, a further, deeper sliding surface was recognized shortly after the event, which could not be stabilized by the surcharge fill. (Figure in full paper). The bedding planes mentioned above dip at 18–20° in slope direction.
- Geology > Geological Subdiscipline > Geomechanics (0.68)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.36)
- Construction & Engineering (1.00)
- Transportation > Ground > Rail (0.71)
- Management > Professionalism, Training, and Education > Communities of practice (0.71)
- Data Science & Engineering Analytics > Information Management and Systems > Knowledge management (0.71)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.68)
- Well Drilling > Wellbore Design > Rock properties (0.43)
Continuum And Discontinuum Modelling of a High Rock Cut
Barla, G. (Dept. of Structural and Geotechnical Engineering, Politecnico di Torino) | Barla, M. (Dept. of Structural and Geotechnical Engineering, Politecnico di Torino) | Chiappone, A. (Geodes srl) | Rabagliati, U. (Geodes srl) | Repetto, L. (Geodes srl)
ABSTRACT The paper describes the application of both continuum and discontinuum modelling to the study of the stability conditions of the Alpetto mine, a high rock cut located in Cesana Brianza (Italy). The main objective is to provide valuable information for future mine planning and for the assessment of the stability conditions of the abandoned high rock cuts. Continuum modelling involved the applications of the finite difference method, whereas the distinct element method was used for discontinuum modelling. RESUME L'article decrit l'application des methodes de modelisation continue/discontinue pour l'etude des conditions de stabilite de la mine d'Alpetto, situee à Cesana Brianza (Italie). Le but du travail consiste à determiner des paramètres utiles vis-à-vis du projet et d'estimer les conditions de stabilite de l'amas rocheux au terme de l'exploitation de la mine susmentionnee. La modelisation continue a implique l'application de la methode des differences finis alors que la methode des elements distincts a ete utilisee pour la modelisation discontinue. KURZFASSUNG Der Artikel beschreibt die Verwendung der Modellierung von continuum und discontinuum zur Untersuchung/Studium der Stabilitatsbedingungen von der Alpetto Mine, hohe Aushubsfront in einer Felsmasse die sich in der Gemeinde von Cesana Brianza befindet. Das Hauptziel dieser Arbeit ist die Festlegung von Parametern die zur Planung nuetzlich/behilflich sein können sowie auch die Möglichkeit zur Analyse/Auswertung der Stabilitat der Felsmasse-Front nach Aufhebung der Nutzung derselben. Die continuum Methode/Analyse wurde verwendet durch Unterstuetzung der Finite Differenz Methode da man fuer die Analyse der discontinuum (Fels als discontinuum beschrieben) der Distinct Elemente Methode verwendet hat. Introduction Rock slope stability covers a wide area in geomechanics from geological, geomorphological and hydro-geological characterization to the assessment of strength-deformability properties of the rock mass and discontinuities at different scale. Of great relevance are both the understanding of external forces (i.e. groundwater influence, seismicity, external loading) and stabilization measures (i.e. drainage, reinforcement, anchoring, etc.) when applied in order to prevent and/or control instability from developing. By restricting to modern numerical modelling methods, one should recognize that he has the option to choose between equivalent continuum and discontinuum procedures. However, when dealing with rock slopes, the importance of discontinuities and description of their characteristics in controlling the relevant physical and mechanical processes points out the role of discontinuum modelling. Continuum Modelling The use of continuum modelling in slope engineering leads to the representation of the constitutive equations of the rock mass comprised of the discontinuities and rock material properties by using the empirical equations given by Hoek and Brown (1997) in order to obtain the rock mass properties of the equivalent continuum. However, great care is required, as clearly stated by the proponents of such equations: even rock masses which appear to be good candidates for the application of equivalent continuum modelling may be intercepted by discontinuities controlling stability conditions. Continuous formulations based on the finite element method (FEM) and the finite difference method (FDM) should therefore be considered restrictive in their applicability to the analysis of rock slopes. However, there are obvious cases where, to some extent.