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Technology
Field Trials of Thin Sprayed-on Membranes For Drift Support
Tannant, D.D. (School of Mining and Petroleum Engineering, University of Alberta) | Barclay, B. (INCO Limited, Copper Cliff) | Espley, S.J. (INCO Limited, Copper Cliff) | Diederichs, M.S. (Geomechanics Research Centre, Laurentian University)
ABSTRACT: A polyurethane product called Mineguard was sprayed on the roof and walls of two tunnels to determine the effectiveness of thin sprayed-on membranes for tunnel support. A continuous membrane that is firmly adhered to the rock creates effective support and is resistant to damage from blasts and scoop abrasion. Careful rock scaling, cleaning, washing, and drying are essential for good adhesion. Stress fractured or slabby ground can result in a "cantilever" loading mechanism in a membrane liner which can progressively tear the membrane and result in a fall of ground. A robotic arm is required to spray a continuous membrane up to the face of a freshly blasted round and to minimize the cantilever loading mechanism. 1 INTRODUCTION INCO Ltd. has been investigating the use of rapidly deployable, sprayed-on membranes for ground support. Initial work focused on evaluation of the physical and chemical properties (including toxicity and flammability) of various products. A polyurethane product called Mineguard was one of several products selected for further laboratory and field tests. Two field trials were designed to assess the in situ performance of Mineguard. Mineguard is made from two reactive chemicals, one being a resin and the other a catalyst. The two chemicals are pumped at a 1:1 ratio through a heated hose and as they mix at the tip of the spray gun a chemical reaction begins immediately. The material sets up within about 20 s creating a tough flexible coating that adheres to the rock surface (Archibald et al. 1992; 1997, Espley et al. 1996). The field trials were conducted at depth of 1295 m within a mine operating in the Sudbury basin. The area selected for the evaluation was a narrow-vein orebody that was being mined using a drift and fill method. Drifts at these depths in the mine experience stress-induced fracturing. The fractures occur subparallel to the roof. The primary function of the sprayed-on membrane is to maintain interlock between pieces of rock and to support the stress-induced slabs that are created as well as any potential small unstable wedges created by intersecting joints at the roof. 2 FIELD TRIAL # 1 The first trial involved the application of Mineguard as primary support for a drift being driven along the strike of a steeply dipping 0.2 to O.5-m wide vein of sulphide ore. The drift was excavated as part of a drift-and-fill mining method for the narrow vein and it was the second of many drifts that were planned in order to mine the vein in a bottom up mining sequence. Figure 1 shows the location of the test drift on the 4250 foot level of the mine (1295 m deep). The first cut (drift) excavated was immediately below the left wall of the test drift. The test section of the drift comprised eight rounds (individual blasts) with spans that ranged between 1.5 and 3.2 m and heights that ranged between 2.1 to 2.7 m. The first six rounds were supported with Mineguard and the final two were supported with welded-wire mesh and bolts. The drift was prepared for the Mineguard application after each blast by mucking out the broken rock, scaling any loose rock, and washing the roof and walls. The adhesion of polyurethane to rock can be adversely affected by wet rock. Therefore, each cleaned and washed round was allowed to dry under good ventilation conditions before the Mineguard was sprayed onto the rock. Figure 2 shows the appearance of the test drift after application of Mineguard to the first three rounds. The Mineguard was sprayed on the exposed roof and walls after each round is blasted, mucked,' and washed The face of the drift was not sprayed. A thickness of 4 mm was specified for the roof while only 2 mm of Mineguard was required for the drift walls. Generally the actual Mineguard thickness exceeded these specifications. Mineguard is white in colour, which helps to improve the lighting situation underground.
ABSTRACT: Some of the significant developments in the field of mining rock mechanics are reviewed. Three time periods are considered: pre-history to 1960, 1960 to 1983, and 1983 to date. Significant advances were made in this field during the middle period, which is defined as the renaissance era. In the most recent and current period research activity in this field has declined and the emphasis has been on transferring knowledge to mining operations. The research needs for mining rock mechanics as we move into the 21 century are considered. RÉSUMÉ: Certains des developpements significatifs de la mecanique des roches appliquee à l'exploitation minière sont passes en revue. Trois periodes sont considerees; de la prehistoire à 1960, de 1960 à 1983 et de 1983 à aujourd'hui. D'importants progrès ont ete accomplis durant dans la 2ième periode, que I'on definit comme une ère de renaissance. Durant la dernière periode, la recherche en geomecanique a diminue d'intensite au profit de la mise en application des connaissances existantes dans l'industrie minière. Alors que nous entrons dans Ie 21ième siècle, les besoins de recherche de I'industrie minière en mecanique des roches sont consideres. ZUSAMMENFASSUNG: Dieser Überblick schilderet einige der bedeutungsvollsten Entwicklungen in der Bergbaurock mechanik, und fuehrt uns durch drei Epochen des Bergbaus. Prahistorisch bis 1960, 1960 bis 1983, und 1983 bis Heute. Bedeutungsvolle Entwicklungen erfolgten wahrent der mittleren Epoche, der Renaissance. In den letzten undo heutigen Epochen sind Forschungsactifitaten zurueckgegangen, der Schwerpunk beschrankte sich auf die Üebertragung von Wissen auf Bergbauunternehmen. Übergehend in das 21. Jahrhundert ziehen wir in Betrachtung das Beduerfnis fuer Forschung in der Bergbaurockmechanik. 1 INTRODUCTION We make a case that the renaissance period (in the sense of a period of vigorous artistic and intellectual activity) for the field of mining rock mechanics, and perhaps rock mechanics generally, was from (roughly) the beginning of the 1960s to (again roughly) 1983, the year of the Fifth Congress of the International Society for Rock Mechanics. The design of excavations for mining has, of course, occupied mankind from the dawn of history and numerous research workers and mining practitioners had, prior to this time, made important contributions to the mining rock mechanics field. However, the rapid global expansion of mining activity following World War II created an urgent need to improve the design of rock excavations. In the 1950s and 60s mines were being opened at an unprecedented rate, new mining techniques were being introduced, and mines (both surface and underground) were operating at hitherto unknown depths. This activity highlighted the need for a more scientific approach to excavation design. This need attracted the interest and attention of some very talented people at a number of centres around the world. We begin this paper by, reviewing briefly the prerenaissance period of rock mechanics. Next we discuss some of the major issues identified for mining rock mechanics during the 1950s and'60s. We discuss the leaders who emerged during the '60s, '70s and early '80s to tackle these issues and we review some of the main approaches that were developed in this period to solve these problems.. The post-renaissance period (1983 to today) has been one of consolidation of knowledge, refinement of technique, incremental advances, and, importantly, transfer of knowledge from the research specialist to the consulting engineer. In keeping with the trend in other industries, today a mining company is more likely to outsource (to use the current jargon) to consultants the bulk of its rock mechanics needs than it is to employ a number of its own experts in this field. We comment on this trend and, in particular, we highlight the need to manage this interface between consultant and mining operator well, in the interests of both mine safety and mining productivity.
- North America > United States (1.00)
- Africa (1.00)
- North America > Canada (0.93)
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- Research Report > New Finding (0.45)
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- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Mineral > Native Element Mineral > Gold (0.93)
- Materials > Metals & Mining > Coal (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Metals & Mining > Gold (0.93)
- Government > Regional Government > North America Government > United States Government (0.46)
- Asia > India > Karnataka > Kolar Gold Field (0.99)
- Oceania > Australia (0.91)
- Europe > Russia > Northwestern Federal District > Komi Republic > Timan-Pechora Basin > Pechora-Kolva Basin > Usa Field (0.89)
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ABSTRACT: This paper investigates the mechanism of slope displacement, the effectiveness of stabilization measures, using the results of long-term monitoring of the unstable behavior of two large excavated rock slopes with elevation differences of about 300 m. The study also evaluates the influence of joints on slope behavior through numerical analysis. Finally, technical guidelines for the stabilization of large excavated slopes are introduced. RÉSUMÉ: Cet expose porte sur 1'etude du mecanisme du glissement de terrain en roches qui ferment des parois d'excavation inclinees, ainsi que sur I'efficacite des mesures visant à leur stabilisation, à l'aide des resultats d'observation à long terme de deux grands paquets de couches rocheuses qui tendent à glisser, sur des parois d'excavation inclinees, dont la hauteur atteint quelque 300 m. De plus, I înfluence des diaclases sur le comportement des parois inclinees sera etudiee au moyen d'une analyse numerique. En dernier lieu, des regles de conduite techniques sont indlquees, pour assurer des parois inclinees de grandes excavations. ZUSAMMENFASSUNG: Diese Studie untersucht den Mechanismus der Böschungsverschiebungsowie die Wirksamkeit von Maβnahmen zur Stabilisierung unter Verwendung der Ergebnisse von langfristiger Überwachung des instabilen Verhaltens zweier ausgegrabener Gesteinsböschungen mit Höhenunterschieden von etwa 300 m. Die Studie bewertet auch den Einfluβ von Fugen auf Böschungsverhalten durch numerische Analyse. Schlieβlich werden technische Richtlinien fuer die Stabilisierung groβer ausgegrabener Böschungen vorgestellt 1 INTRODUCTION The present study focuses on two large excavated rock slopes with elevation differences of about 300 m or more and of different rock structure. Both slopes were monitored over years from the occurrence of the first unstable behavior to the stabilization or collapse. On the basis of the data obtained from these measurements, this paper investigates the mechanism of slope movement and the effectiveness of stabilization measures in terms of both measurement data and numerical analysis results. 2 SLOPE DISPLACEMENT AND CHANGES IN UNSTABLE BEHAVIOR 2;1 Case 1:Excavated slope of Misogawa Dam quarry (1) Geological structure and changes in unstable behavior This slope is composed of alternations of Triassic ~ Jurassic sandstone and slate layers. As shown in Figure 1, the layer dip at about 40° to 60° toward the mountain. The slate layers SI-3, SI-4 and SI-5 are at least about 20 m thick each. These layers contain highly sheared zones, which are thought to have been created as a result of creep. The lower half of S1–4 contains argillized weak zone. SI-3 and SI-5 also have sheared zones, but they are much, smaller than those in SI-4. Figure 2 shows a plan view of the slope. Excavation of the slope began in April 1985 at around EL 1420 m by bench cutting. In May 1989, when the excavation at EL 1180 to 1160 m (road) began, the stability of the slope, particularly in the right side from the intersection line (A-A) where the slope surface changes direction began to fall sharply until the entire slope surface became unstable. The maximum rate of displacement, according to electro-optical distance measurement (hereafter termed "distance measurement") results, was about 6 mm/day, and a cumulative displacement of more than 250 mm occurred locally during the one year from April 1989. Therefore, excavation was suspended, and stabilization measures including drainage tunnel (length: 100 m) and prestressed anchors (about 350 anchors; 22 to 34 m in length) were taken. As a result, the slope movement stopped. The slope angle for subsequent excavation below the road was changed, and in July 1990 excavation was resumed.
- Geology > Rock Type > Metamorphic Rock > Slate (0.46)
- Geology > Rock Type > Sedimentary Rock (0.39)
ABSTRACT: Prediction of roof falls inside the goaf during extraction of coal was attempted by many investigators on the basis of convergence monitoring data. In majority of the cases the data was collected by daily manual measurement of roof to floor convergence. Exact information about sharp changes in convergence a few hours before and after the fall is not available from the manual systems. Many empirical relations suggested for prediction of falls are based on daily convergence data. These relations were applied in the present case and the variations of these indices with reference to the system data was studied for selection of reliable warning limits for indication of impending falls. The change in rate of roof convergence plays a decisive role for the stability of collapse of mine roof. Continuous monitoring of rate of change in roof convergence helps in predicting and averting mine disasters. Keeping this in view NIRM developed Microcontroller based Rate of Convergence Monitoring System (M-RCMS) which detects roof strata convergence continuously and analysis on real time for getting rate of change in roof convergence. The M-RCMS system used at GDK-10 Incline of Ramagundem area, SCCL for surveillance of the adverse strata behaviour in advancing galleries while extraction of blasting gallery panels. RÉSUMÉ: La pre'diction du toit quit tombe dedans le pendant l'extraction du charbon e'tait essaye'e par plusieurs investigateurs a' la base des donne'es du moniteur au convergence. Dans la majorite' des cas les donne'es e'taient ramasse'es par un mesure manuel quotidien du toit au parquet au convergence. L'information exacte par rapport des changements aigus en convergence quelques heures avant et apre'es la tombe'e n'est pas disponible des syste'mes manuels. Beaucoup des relations empiriques suggere'es pour la pre'diction des tombe',es sont base'es sur les donne'es du convergence quotidien. Le changement dans Ie cours du convergence du toit joue un ro^le de'cisif pour l'analyse de la stabilite' de l'effondrement du toit de la mine. Un moniteur contiuel du cours du changement du convergence du toit assite dans la pre'diction, et l'e'vasion des de'sastres aux mines. Tenant ce point de vue NIRM a de'veloppe' un Systeme au Moniteur du Cours de Convergence (M-RCMS) qui detectc le niveau du toit converge' continuellement et analyse au temps actue1pour avoir le cour du cbangement du convergence du toit. ZUSAMMENFASSUNG: Voraussage von hangender Schicht innerhalb der unzuganglicher Stelle wahrend der Gewinnung der Kohle wurde von vielen Forschem auf Grund dec Konvergenz- Überwachungs-Datenversucht. In den meisten Fallen wurden die Daten taglich durch manuelle Messung von der Konvergenz der Schicht zu Boden gesammelt. Genaue Information ueber starke Änderungen der Konvergenz vor und nach dem Sturz ist durch diese Systeme nicht vorhanden. Viele vorgescblagenen empirischen Verhaltnisse der Voraussage von Sturzen send an die taglichen Konvergenz basiert. Die Änderung der Konvergenzgeschwindigkeit des Dachs hat eine entscheidende Rolle fuer die Festigkeitanalyse der Einsturz des Bergwerksdach. Standige Überwachung der Konvergenzgeschwindigkeit des Dechs hilft bei der Voraussage und Vermeidung der Bergwerkkatastrophen. Mit dieser Ansicht entwickelte NIRM ein Mikro-Regler-basiertem Konvergenzgeschwindigkeits- Überwachungssystem (M-RCMS), das die Gebirgsschicht-konvergenz stetig aufdeckt und analysiert auf Echtzeit um die anderungsgeschwindigkeit der Dachkonvergenz zu bekommen. 1 INTRODUCTION Blasting gallery method of working consists of drivage of development galleries along the, floor of a thick seam. The entire thickness of the seam would be blasted but successive ring blasts while retreating along the galleries. At GDK 10 incline a large panel of 1 Km X 150m was divided into sub-panels of 150m X 150 m by driving a main rise. A barrier of 20 to 25 m was left in between the sub-panels was further divided into two parts by a central main rise. From this rise, rooms were driven at 13 to 15 m apart. The galleries were 4.2 m in width. Thus, a solid coal pillar of about 9 to 11 m width was formed between the two successive galleries. The width of the main rise and the central rise was 4.7 m. The method of working along with location of the convergence stations during different phases of extraction is shown in fig. 1
ABSTRACT: This paper describes a displacement monitoring approach for the assessment of slope stability. A new displacement monitoring system using the Global Positioning System was developed together with a data processing method for improving monitoring results. Practical applications of the system to an open quarry and a landslide slope are discussed. RÉSUMÉ: Cet article decrit un deplacement surveillant l'approche pour I'evaluation de la stabilite de pente. Un nouveau système de surveillance de deplacement utilisant le GPS a ete developpe ainsi qu'une methode informatique pour ameliorer des resultats de surveillance. Des applications pratiques du système une carrirè ouverte et une pente d'eboulernent sont discutees. ZUSAMMENFASSUNG: Dieses Papier beschreibt eine Distanzadresse, die Annaherung fuer die Einschatzung der Stei-. gungstabilitat ueberwacht. Ein neues Distanzadressemessen-System, das den GPS verwendet, wurde zusammen mit einer datenverarbeitenden Methode fuer das Verbessern von Messen-Resultaten entwickelt. Praktische Anwendungen des Systems zu einem geöffneten Steinbruch und zu einer Landslidesteigung werden behandelt. 1 INTRODUCTION Slope stability is usually assessed using empirical and/or mechanics methods. Engineers often meet with difficulties when judging the real stability of slopes with such conventional methods. Monitoring slope displacements can help them to evaluate slope stability in practice. The author and his colleagues have been developing a new displacement monitoring system using the Global Positioning System (GPS), which is designed to automatically monitor displacements of the ground. The system can simultaneously measure the three-dimensional displacements of many points over an extensive area and display the results on a monitor screen in real time.. '1 This paper presents a displacement monitoring approach for the assessment of slope stability. In addition the GPS displacement monitoring system is outlined together with a method of data processing. Practical applications of the system to an open quarry, and a landslide slope are demonstrated. 2 DISPLACEMENT MONITORING APPROACH FOR THE ASSESSMENT OF SLOPE STABLITY. Displacement monitoring is commonly conducted to confirm safety by detecting the signs of failure. The conventional assessment method for slope stability is mainly, based on force equilibrium. There are only a few methods for assessing stability based on displacement monitoring. Therefore, it is necessary-to develop a method which can evaluate displacement monitoring results. Figure l shows the displacement monitoring approach being developed by the author It is composed of the following three methods:Time series analysis of continuous monitoring results The first method is the simplest among the three methods I described here. Its purpose is the estimation of the exact value of measured displacements and the prediction of the final displacement and/or the failure time from the time series data of the displacements.The estimated and the predicted displacements and velocities should be compared with the critical values for assesaing stability. Geometrical analysis of rock discontinuities and measured displacements In addition to the time series data of measured displacements, the second method uses the geometrical data of the, slope and its rock discontinuities (i.e., the strike the dip, etc.). Geometrical data is easy to obtain compared with stress, force, and mechanical parameters. The purpose of the method is to evaluate a potential failure mode, i.e., plane sliding, wedge sliding and toppling, and a potential failure area. Back analysis of the measured displacements using mechanics The third method uses mechanics. It includes a back analysis method and a conventional limit-equilibrium method. A back analysis of measured displacements is conducted in order to estimate the strength parameters of a rock mass. In order to calculate the factor of safety, the limit equilibrium method is used together with the back-analyzed strength parameters. The results obtained from the mechanics method is most useful in quantitatively assessing the stability and designing stabilization works.
ABSTRACT: Several important road tunnels in rock were built in Portugal in the last years. The author was involved in the geotechnical studies for their basic designs, including rock mass zoning and definition of excavation and support methods, and in the intensive close-loop monitoring of the tunnels during the construction, which appeared as the most effective tool for the optimization of these underground structures. RESUMÉ: Plusieurs tunnels routiers en roche ont ete construits au Portugal pendant les dernières annees. L'auteur a ete engage dans les etudes geotechniques pour leur projet preliminaire, y inclus Ie zonage du massif rocheux et la definition des methodes d'excavation et soutenement, et a aussi conduit l'auscultation intensive des tunnels pendant la construction sous une optique de conduite assistee des travaux, qui s'est montree l'outil le plus effective pour l'optimization de ces ouvrages souterrains. ZUSAMMENFASSUNG: Mehrere wichtige Straβentunnel in Felsen wurden in Portugal wahrend der letzten Jahre gebaut. Der Verfasser war beteiligt an den geotechnischen Untersuchungen fuer ihre Vorprojekte, einschlieβlich der Gebirgseinteilung und der Definition der Abbau- und Ausbaumethoden, und der intensiven meβtechnischen Überwachung mit Rueckkopplung der Tunnel wahrend des Baus, die sich als das effektivste Hilfsmittel fuer die Optimierung dieser Arbeiten herausstellte. 1 INTRODUCTION Reliable geotechnical information required for the final design of tunnels can only be obtained, in most cases, during the construction, due to severe limitations of the cost-benefit relation of the geotechnical studies for the preliminary design. In spite of the interest of such studies, the results of any structural analysis and (or) empirical methodologies at design stage should be considered working hypotheses subject to confirmation or modification during construction, rather than definitive solutions to be built up on site. Therefore, the observational method, based on a closed-loop intensive monitoring of the tunnel behaviour appears as the most effective means for the optimization of tunnel construction. In Portugal, the construction of the road tunnels of Gardunha, Varosa and Regua started with detailed preliminary designs, establishing the geotechnical zoning of the rock masses and the most probable caracteristics of such zones, from which the likely most suitable construction methods and primary and secondary supports were derived. However, intensive monitoring during the construction, following detailed tunnel survey plans, have played the major role in the up-dating of the construction methods and support requirements to the effective geotechnical conditions revealed by the excavations. Such decisions were taken under consensus by a working team involving engineers of the owner (Junta Autónoma de Estradas, JAE), his technical adviser (Laboratório Nacional de Engenharia Civil, LNEC), the designer (COBA) and the contractors. Convergence and settlement measurements, and piezometer, inclinometer, multiple-borehole extensometer readings and detailed geotechnical mapping of the excavated surfaces were currently carried out included in closed-loop monitoring procedures as basic tools for the final design of the tunnels. The intimate connection between monitoring results and constructive decisions is dully emphasized in the paper. 2 THE GARDUNHA TUNNEL 2.1 Geotechnical studies and design This two-directional tunnel, crossing the Gardunha mountain included in the IP2 highway (northeast central zone of Portugal) is about 1600 m long, with a 220 m maximum overburden and a 84 m cross section area, excavated in granitic and schistous rock masses. The rock weathering reaches a depth of about 50 m, thus affecting mainly the portal zones, where the tunnel was constructed in a saturated residual granitic soil with random boulders. The geotechnical studies for the detailed preliminary design included surface reconnaissance, borehole drilling, seismic tomography, Lugeon and dilatometer in situ tests and laboratory ones such as uniaxial compression and joint shear tests.
- Construction & Engineering (0.54)
- Energy > Oil & Gas > Upstream (0.50)
ABSTRACT: In order to study the possible damage of excavation and to arrange operative corrections for the enlargement in a built up area near tunnels, several sensors monitoring the rocky masses and several vibrometric stations have been located. Both the systems were managed by an intelligent terminal microcomputer linked to a Data Analysis Control located 1120 km away. The real time monitoring of 3 years of work showed that the use of mechanical tools didn't cause any vibration dangerous to buildings, or the activation of rocky bodies. RESUME: Pour analiser les dommages qui pouvaient deriver de I'utilisation des moyens mecaniques necessaires pour creuser des tunnels près d'un terrain urbanise et dans Ie but de predisposer les modifications indispensables, on a mis en place des stations vibrometriques et on a place sur les parois rocheuses des transducteurs de position. Ces deux systhèmes d'analyse sont geres par un micro-ordinateur de base à 1120 km. Le suivi à distance pendant les trois annees des travaux a demontre que Ie moyens mecaniques n'ont provoque ni vibrations dangereuses pour les batiments ni eboulements de masses rocheuses. ZUSAMMENFASSUNG. Um den Grad möglicher Schaden zu analysieren, die infolge Aushubarbeiten in nahegele-genen Tunnels mit Frasvortrieb und Erweiterung mit mechanischen Geraten auf eine urbanisierte Zone einwirken wuerden und eventuelle Korrekturen der Arbeitsweise vorzubereiten, wurden Meβstationen zur Erfassung von Er-schuetterungen angebracht. Die Felswande wurden auch mit Bewegungsmessem versehen. Beide Meβsysteme wurden ueber einen hochentwickelten Mikrocomputer betrieben, der mittels einer Übertragungsstrecke von 1120 km Lange an ein Datencenter angeschlossen war. Die Kontrolleinrichtung hat wahrend der 3 Jahre dauemden Arbeiter gezeigt, daβ der Einsatz der mechanischen Gerate weder gefarliche Erschuetterungen fuer die Gebaude, noch Felsstuerze verursacht hat. 1 INTRODUCTION National Road n. 18 variant, between km 302+500 and 307+000, along the built-up area of Guardia Piemontese Marina in Calabria (Italy), develops for nearly the totality, tunnels dug into metamorphic and sedimentary cliffs of the massive hills overhanging the village (Fig.1). Beginning from south-east, these are represented by sandstones making passage to slates and, more ahead, to quartz-phillites pertaining to the medium Trias of the Calabrian Coast, put into non-bedded crystalline limestone. According to Table 1, the cliffs present Figure 1- Location plan of National Road 18 variant. geomechanical characterisation from average to poorer, being it included, between Barton's V and VII and Bieniawski's III and V. This area is affected by several fissures splitting up into heaps of different volume pointed to landslide. In order to gather valid elements about vibrations transmitted by digging works, and their incidence on possible mobilization of the massive premises with consequent damage on the overhanging buildings, the National Board of Roads. (A.N.A.S.) has predisposed the use of devices planned to monitor these phenomena. 2 MONITORING OF THE VIBRATIONS 2.1 In order to analyse the vibrations induced on the rocky bodies and on the loose grounds by 0 4.94 m slot cutters and enlarging mechanical tools, eight vibrometric stations were located in the most significant places. 2.2- To such aim, the measurement transducers were put in direct contact to the rocky formations within traps of 0.5–0.7m in depths and placed in diggings of l.5xl.0x0.5 m large. Over it, a sand thick to isolate from spurious vibrations and supported by few resin glass boxes-whose overall size was 0.6x0.3x2 m. The boxes were braced and provided with an antenna holder.
- Geology > Rock Type > Sedimentary Rock (0.55)
- Geology > Structural Geology > Tectonics (0.46)
ABSTRACT: It is well known that a part of soft rock shows the time dependency, that is, the deformation appears even in no excavation, the displacement gradually increases after the face advances far away, and the displacement converges slowly. In this study, the ground properties including the time dependent parameter were obtained by reverse analysis applying the 3-dimensional elasto-visco-plastic FEM to the convergence in-situ data with time dependency. It was confirmed that the deformation behavior of the tunnel in soft rock with time dependency can be exactly approximated, by comparing the displacement obtained by direct analysis according to the reverse analysis results with the measured one. RÉSUMÉ: On sait que les sols formes de roches meubles montrent parfois les effets du temps, à savoir une augmentation de la deformation même sans excavation, une augmentation graduelle du deplacement après que la paroi frontale ait ete percee plus avant et une lente convergence du deplacement. Dans cette etude, les proprietes du sol, y compris Ie paramètre des effets du temps, ont ete determinees par analyse inverse et application du FEM elasto-visco-plastique à 3 dimensions aux donnees de convergence in-situ avec effets du temps. II a pu alors être confirme que le comportement à la deformation des tunnels en roches meubles avec Ie temps pouvait être estime avec precision en comparant Ie deplacement obtenu par analyse directe basee sur les resultats de I'analyse inverse avec le deplacement mesure. ZUSAMMENFASSUNG: Eigenschaften wie die zeitliche Abhangigkeit fortsehreitender Formanderungen bei manchen Sedimentgesteinen auch wahrend Unterbrechungen der Tunnelausschachtungen, kontinuierliche Deformation nach ausreichendem Vordringen der Abbaustelle und die langsame Konvergenz sind allgemein bekannt. In der vorliegenden Studie wurden die eine zeitliche Abhangigkeit aufweisende Meβwerte der Innenmaβe bei in Sedimentgesteinen vorangetriebenen Tunneln dazu verwendet, die geophysischen, einschlieβlich der zeitabhangigen, Eigenschaften elastisch, viskös-plestischer Körper mittels 3- dimensionaler Finite-Element Methode (FEM) ruecklautig zu analysieren. Durch gewöhnliche Analyse der mit der ruecklaufigen Analyse erhaltenen geophysischen Werte konnte nachgewiesen werden, daβ mit dieser Methode die zeitabhangigen Eigenschaften des geologischen Deformationsverhaltens mit hoher Genauigkeit angenahert werden können. 1 INTRODUCTION In order to construct the tunnel reasonably, it is important to take a balance between the safety and the cost by observing the ground behavior and the support behavior. Therefore, the observational method, which collects the various in-situ data and reflects the analysis results in the design and in the execution, is widely adopted. So far, various methods to reflect the measurement to the design and to the execution have been proposed. However, the sophisticated technique to obtain the ground properties and to analyze the ground behavior is necessary, since the behavior of an individual tunnel mainly depends on the ground properties. On the other hand, it is well known that a part of soft rock shows the time dependency, that is, the deformation increases even in no excavation, the displacement increases gradually after the face advances far away, and the displacement converges slowly. These time dependent behavior of the ground do not come from the release of the original earth pressure due to excavation, but the time dependent characteristics of the ground. Therefore, in these cases, an elastic or an elasto-plastic model without time dependency cannot predict the convergence time of displacement, the amount of the final displacement, the state of the support and the state of the ground because these models can not represent the time dependent characteristics. Moreover, numerical analysis of tunnel are usually carried out by two dimensional analysis because the final state of the ground around tunnel can be regarded as a plane strain state, and the calculation time and a capacity of the computer are limited.
- Geology > Rock Type (0.90)
- Geology > Geological Subdiscipline > Geomechanics (0.47)
ABSTRACT: In this paper, an analysis of the physical meaning of rock mass classification parameters allows for a probabilistic interpretation of the RQD index. This modified RQD has a number of interesting properties. Further, some of the RQD's drawbacks are addressed. The behaviour of the modified RQD allows it to explain and include effects from other rock mass characterisation parameters. Combining this approach with observations based on data from Greek tunnelling projects, the authors propose that the output from classification systems may be reached using a smaller number of input parameters. RQD and groundwater seem to be important parameters and, in some cases, sufficient, for describing aspects of the behaviour of the rock mass. RÉSUMÉ: Une modification de I'indice RQD est proposee suite à une interpretation probabiliste de son definition physique. Cet indice ainsi modifie possède un nombre des proprietes interessantes. Quelques defauts du RQD dans sa forme originale sont surpasses. Le comportement du RQD modifie lui permet d'expliquer et comprendre des effets d'autres parametres de caracterisation des masses rocheuses. Cette approche en combinaison avec des observations basees sur information tiree de projets de tunnels en Grèce, a permis aux auteurs de proposer que le resultat des systèmes de classification peut être obtenu utilisant un nombre redui des parametres. II paraît que Ie RQD et I'eau dans le massifrocheu sont les paramètres les plus importantes pourla description des aspets du comportement du massif et, dans certaines cas, sont même suffisantes. ZUSAMMENFASSUNG: Es wird eine Modifizierung des RQD-Indexes vorgeschlagen, die fuer eine probabilistische Interpretation seiner Bedeutung geeignet ist. Dieser modifizierte RQD hat eine Reihe von interessanten Eigenschaften. Einige Nachteile des RQD in seiner urspruenglichen Form werden ueberwunden. Ocr modifizierte RQD erlaubt die Erklarung und den Einschluβ von Parametern anderer Felsmassen Charakterisierungen. In Kombination mit Beobachtungen, die auf Daten anderer griechischer Tunnelprojekte basieren, schlagen die Autoren vor, unter Benutzung von einer geringen Zahl von Parametern die Klassifizierung vorzunehmen. RQD und Grundwasser scheinen die wichtigsten Parameter zu sein und in vielen Fallen ausreichend, um das Verhalten der Felsmasse zu erfassen. 1. INTRODUCTION A usual problem in designing structures in rocks is to correctly estimate and model the mechanical behaviour of the rock mass. This is usually achieved by combining laboratory measurements on rock samples from boreholes with indices constructed by assigning values to various rock mass characteristics. Most of these rock mass characteristics are unknown at the preliminary stage of design. Estimations are made based on experience, existing knowledge of the geology of the area and examination of core usually available from few sparse boreholes. Classification systems that provide a single output index have been proposed and are quite popular. This. output index is used either to provide estimates for the parameters needed for modelling rock mass behaviour, or for empirically selecting support patterns, excavation methods etc. The various parameters interfering with the construction of the final index are open to a wide interpretation, producing differing results and making this procedure quite arbitrary at the preliminary stage. This problem can be approached by attributing mathematical constraints, as well as appropriate interpretation of the physical influence of each rock characteristic on the indices used. Often, it is the opposite that is applied, as assigning values to indices corresponds to creating a more or less unclear image of the rock mass considered to reflect the lack of adequate information.
ABSTRACT: ' Engineers are more concerned with the properties of jointed rock mass than intact rock or rock joints. Their interest in intact rock and rock joints is basically to derive the properties of the jointed rock mass from those of intact rock and rock joints for a known joint fabric. It is stiffnesses of rock joints which is required for assessing the deformability and strength of the jointed rock mass to predict the settlement or collapse of rock structures. For the numerical analysis, the stiffnesses of rock joints are required which can be found out from the laboratory tests or in-situ tests, The failure criterion of a rock discontinuity is usually non-linear. The angle of shearing resistance decreases as the level of normal effective stresses increases. Empirical strength criteria in the form of power or logarithmic relationship have been reported in literature. The main shortcoming of these proposals is the validity in the limited stress range and the lack of physical meaning. In this paper, it has been shown that the same or similar failure law can be derived for rock discontinuities from in-situ shear tests on rock joints with non-rigid asperities. RÉSUMÉ: Le genie est pIus s'interesse aux qualites du materiel du rocher joint quele rocher intact ou les joints du rocher. Leur, interêt dans le rocher intact et les joints du rocher est au fond à deriver les qualites du materiel du rocher joint du rocher intact et des joints du rocher pour une etoffe jointe deje connue. C'est la rigidite des joints du rocher qui est recquise pour faire l'asessement de la deformabilite et la resistence du materiel du rocher joint de manier à poedire l'etablissement ou lecroullement des structures du rocher. Pour l'analyse numerique, la rigidite des joints du rocher sont recquises qui peuvent se rouver dans les epreuves laboratories ou dans les epreuves en situ. Le critere pour le manque de la discontinuite d'un rocher est general non lineaire, L'angle de reesistence de la tonte effective normale diminue quand le niveau dune tension s'augmente. Le critère de la force empirique dans la fovme de la force de la capacite ou la relation logarithmique est comple rendu en litterature, L'erreur principal de ces propositions est la validite dans Ie rayon de la tension limite et le manque d'une signification physique. ZUSAMMENFASSUNG: Die Ingenieure beschaftigen sich mehr mit der Eigenschaft der vollstandigen Gesteinmaβe als intakt Gesteins oder Gesteingelenks. Sie interessieren sich fuer die Eigenschaft des intakt Gesteins und Gesteingelenks, weil sie hilft die Eigenschaft der vollsandigen Gesteinmaβe zu herleiten und ein wissend einigen Fabrik zu bauen. Es braucht die Steifheit des Gesteingelenks die Deformierung fahigkeit und starke der vollstandiger Gesteinmaβen festzusetzen, die Vereinbarung oder der Einsturz der Gesteinstruktur wird gebracht fuer die zahlenmaβig Analyse, die wird uns - labor od "in situ" Kalkuliert. Die Versaurnnisbedingung in ein Gestein ist meistens nicht linear. Der winked des schere Keristanz vermindertals wird. Level des nomalweises Effektiv Druck Vermchrt. Emperische Stark Kritierium im Formen des Starks oder logarithmische Beziehungen wird im Literatur gezogen. Aber diese Vortragen wird nicht akzeptiert, weil es geht gut nur in ein beschrankt Druck (Streβ) Reihe, (range) und Mangel der phyrische Bedeutung. Diese Papiere zeigt, daß die gleiche oder ahnliche Versaumengesetz kann man von unterbrechenden gestein beurteilen, Es ist Möglich in "in situ" schere Probe urn Gesteingelenken mit nicht-starr Eigenschaften, also die steifheit des Gesteingelenken prasentiert. 1 STIFFNESSES OF ROCK JOINT The pattern of joints, shear zones and faults in a rock mass reduces the effective shear strength to a value much below the intact rock strength, at least in directions parallel to these discontinuities, Where the direction of loading is parallel or sub-parallel to the structural features, the shear strength is governed by the shearing resistance along the rock surfaces of the discontinuity and will generally be much lower. In-situ shear tests have been conducted as per Indian Standard (IS 7746–1975) on the rock mass to assess its shear strength and joint stiffness, In this test, a block of rock cut from the parent rock, is sheared along the rock surfaces of the discontinuity by the horizontal jack, whilst a second jack simultaneously exerts a perpendicular load. This test gives an estimate of the cohesion and angle of shearing resistance of the rock and also the normal and shear stiffnesses of the joint. The block has usually a plan area of approximately 4900 cm, but larger area may be considered [Serafim (1964)].(Equation in full paper) The normal and shear stiffnesses are evaluated from the graph between normal stress Vs vertical deformations