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Energy
ABSTRACT: A rock slope classification scheme leading to slope stability assessment is in development in which factors are introduced to compensate for weathering and excavation disturbance and produce a rating for an imaginary unweathered and undisturbed ‘reference’ rock mass. The classification thence allows assessment of the stability of the existing or any new slope in the reference rock mass, with allowance for any influence of excavation method or (future) weathering. RÉSUMÉ: Un système de classification pour des pentes (naturels ou artificiels) d'un massif rocheux est developpe et resulte en une determination de la stabilite des pentes. Le système comprend des facteurs pour compenser pour l'alteration et l'endommagement par le methode de l'excavation. Le resultat est une appreciation numerique pour un massif rocheux qui n'est pas altere ni creuse - le massif rocheux de 'reference'. La stabilite de la pente nouvelle ou la pente existante est classe en le massif rocheux de ‘reference’ avec des facteurs compensatoires pour l'alteration (future) et l'excavation. ZUSAMMENFASSUNG: Ein Klassifikationssystem fuer die Stabilitat von Felshangen ist in Entwicklung. Das System enthalt Faktoren fuer Verwitterung und Ausbruchsart. Das Resultat ist ein Wert fuer ein Fels der nicht verwittert und nicht ausgebrochen ist - der ‘Referenz’-Fels. Die Stabilitat des neuen oder existierenden Hanges ist dann kiassifiziert im ‘Referenz’-Fels mit Faktoren fuer Ausbruch und (zukuenftige) Verwitterung. 1 INTRODUCTION: Rock mass classification schemes developed for underground works (Bieniawski, 1989, Barton, 1976, 1988, Laubscher, 1990) result in recommendations for support; some systems also apply to rock slope stability (Bieniawski, 1989, Romana, 1985). However, the use of rock mass classifications developed for underground works leads often to unsatisfactory results when applied to near-surface applications such as rock slope stability, and a new rock mass classification system for slopes has been developed based on the Laubscher system. The rock slope classification system was developed during three years of research in the Falset area in the north-east of Spain. Here new roads have recently been built through a mountainous terrain, necessitating a large number of new road cuts. Rocks in the Falset area vary from Tertiary conglomerates to Carboniferous slates and include rocks containing gypsum, shales, granite (fresh to completely weathered), limestone and sandstone, thus giving the opportunity to assess slopes in different materials. Different methods of excavation were used for the old and the new road cuts, allowing comparison of different excavation methods. Road cuts made for old roads some 40 to 60 years ago could be compared to road cuts not more than 4 years old. Also local variations in weathering, the influence of weathering, and the susceptibility of the rocks to weathering as a factor in slope stability could be studied in detail in the area. Existing old and new slopes have been classified and assessed on stability by the staff and students of ITC and the Technical University, Delft. Nearly all slopes have been classified and their stability assessed by more than one person to avoid observer bias. 2 ROCK SLOPE FAILURE MECHANISMS: Slope failure mechanisms such as plane sliding, wedge failure, toppling and, to some extent, buckling are discontinuity related. Also non-discontinuity related agencies such as deterioration of rock material, progressive weathering, intact rock creep, erosion due to (surface-) water and internal water (flow and pressure) can cause slope failures. In a relatively simple rock mass with clearly defined discontinuity sets failure mechanisms related to discontinuities can be analyzed and the stability can be calculated provided the shear strength along the discontinuities can be established. However, such an analytical approach might not be feasible for slopes containing multiple discontinuity sets with large variations of mechanical characteristics.
- North America > United States (0.30)
- Europe > Netherlands > South Holland > Delft (0.25)
- Europe > Spain (0.24)
ABSTRACT: Rock mechanical properties reflect its geological history. The geometry of its crack and fissure network as well as its evolution under a stress or thermal load tends to follow fractal like patterns in space and time. This characterization is also related to the percolation like fluid transport and fracture development in the rock mass under applied pressure or stress load. RESUMÉ: Les proprietes mecaniques des rochas met tent en evidence leur histoire geologique. La geometrie du reseau de fractures et de fissures autant que leur evolution sous tension ou charge thermique sont souvent du type fractal dans l'espace et dans le temps. Cette caracterisation se rapporte aussi à la percolation du type transport des fluides et developpement de fractures dans les masses rocheuses sous compression ou tension. ZUSAMMENFASSUNG: Die mechanische Eigenschafte von Gesteine zeigen ihre geologische Geschicht. Die Geometrie der Bruche und Risse Netzwerk ebenso wie ihre Entwicklung durch Spannungen und thermische Schutllast neigen zu zersteilende Vorbilder in Platz und Zeit. Diese Charakteristik steht auchin Beziehung mit Einsickern und Entwicklung der Bruche in Gesteinemass durch anlegende Spannungen und Schuttlast. 1. GENERALIZED EQUATION OF STATE WITH DAMAGE INCLUDED: Rock mechanical and transport properties reflect its geological history. A microscrack network develops in a crystalline rock after solidification as a result of the interplay of stress and thermal loads imposed by the boundary conditions to which the rock is submitted along its geological history. This process is a very complex one. We try to understand and modellize it by invoking the pertinent physical laws. This equation comprises the elastic strain of the material but excludes the slower creep processes. 2. MICRO CRACK STABILITY: Cohesive forces acting near a microcrack edge represent an internal load that deforms the crack lips and lead to a stress intensity factor which balances the one due to the external loading; the stress field remains thus finite at the crack edge; in the whole cohesive zone the normal stress equals the yield stress. In a slit shaped microcavity, the energy of adhesion W, the maximum stress between the two surfaces σth and the equilibrium spacing are inter-related and can be quantified from first principles (Maugis, 1992). 3. MICRO CRACK PROPAGATION AND CLUSTERING: Microcrackes develop as inter-grain cavitation and as intra and trans-grain microfracture. Fast fracture results from the intensification of the average stress field in the neighbourhood of the edge of a pre-exhisting microcrack. On the other hand, another length is required to characterize the profile, namely the "topothesy", which adds a real measurable scale to the profile and is reflected in the magnitude of the structure function. Poon et al, (1992) studied four types of sedimentary rock and found in all cases a fractal dimension of 1.2 for the crack profiles, which means 2.2 for the crack surface. At the extreme limit of the microcrack network development, one has the rock fragmentation. Barbery (1987), discussed the fragmentation process in connection with the comminution and liberation of minerals and showed how it can be modellized by random geometrical sets of Poisson polyheadra and lead to power-law frequency-size distributions, over a broad size range, in agreement to earlier empirical data and statistical models. Turcotte (1992), interpreted the fractal character of fragment size frequency distributions invoking either renormalization or comminution models and collected experimental evidence of such fractal behaviour in a number of geological instances. In the case of granitic rock, examples give fractal dimensions in the interval 2.2 through 2.5. Wong and collaborators have studied the fractallity of porous media, namely sedimentary rocks.
- Europe (0.69)
- North America > United States (0.47)
ABSTRACT: The general report passes in review the 25 papers included in theme T2, grouping them by the most important topic, and presents some comments of a more general nature on different environmental issues. RÉSUMÉ: Le rapport general passe en revue les 25 communications inserees dans le thème T2, en les groupant par le sujet le plus important, et presente quelques commentaires d'une nature plus generale sur de differents problèmes d'environnement. ZUSAMMENFASSUNG: Der Generalbericht betrachtet die 25, im Thema T2 einbegriffenen Beitrage, wobei er sie nach dem wichtigsten Gegenstand zusammenfaβt, und erbringt einige Kommentare allgemeinerer Art ueber verschiedene Umweltfragen. 1 INTRODUCTION: The Organizing Committee of the Eurock '93 Symposium chose the "Influence of the Environment in Rock Engineering" as theme T2 of the Symposium, and included the following 6 subthemes under that heading:-Global environmental effects; -Heat and mass transport in fractured rock; -Contaminant migration; -Waste disposal; -Underground storage of waste, hydrocarbons, and energy; and -Control of vibrations. In the last years, environmental questions have been receiving an ever growing attention in the scientific meetings, and a first question we may therefore ask, is: Are we really facing new problems, or only rediscovering old ones? Obviously, engineering works have always exerted some influence on the respective environment, and, vice versa, the environment has always exerted some influence on the engineering works. However, the number and the size of the major engineering works is increasing steadily, and, so, also the corresponding disturbance of the respective environment. The current environmental problems are, therefore, of a different scale than those mankind has known for long. On the other hand, our knowledge about environmental issues is also increasing steadily. We are, therefore, nowadays aware of many environmental problems which, not long ago, tended to be overseen. Finally, we are currently faced with engineering works for which there is little or no previous experience (e.g. nuclear waste disposal). Here, we are really facing new challenges, also from the environmental point of view. A second question we may ask, relates to the fact that, apparently, there is a greater awareness of the environmental problems in the rich countries: Are the environmental issues restricted to the developed countries? Rich countries, usually, have already built many, and sometimes also very large (and very expensive) engineering works, and, for this reason, have, quite often, greater environmental problems than the poor countries, where the construction of engineering works is delayed by the economic situation. On the other hand, rich countries, usually, have also invested more in developing their knowledge about environmental questions, and, so, their environmental problems are, very often, recognized much earlier. Finally, and due to the reason that the environmental problems, quite often, do not originate any immediate economic loss, the temptation exists, especially in poor countries, to consider them as negligible in face of the, sometimes large, immediate expenses incurred in their solution. Unfortunately, the solution of many environmental issues still tends to be considered a luxury. A total of 25 papers were included in theme T2, and demonstrate the widespread general interest of the rock mechanics community in the environmental issues. The response to the 6 propounded subthemes was, however, very disparate. While some of the subthemes (Global environmental effects, Contaminant migration, and Control of vibrations) had only very few contributions, the other ones (Heat and mass transport in fractured rock, Waste disposal, and Underground storage of waste, hydrocarbons, and energy) clearly depict the current great concern with the problems of the waste disposal and, specially, of the nuclear waste storage.
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type (0.95)
- Water & Waste Management > Solid Waste Management (1.00)
- Law > Environmental Law (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry > Utilities > Nuclear (0.88)
ABSTRACT: The Siah Bishe Pumped Storage Project is now under construction. The investigation results, the stability analysis and the support concept for the cavern are reported. The powerhouse is arranged in sedimentary and volcanic rocks of Permian age. The frequency and width of bedding parallel shearzones determined the final support concept. The results of stability analyses show distinctly asymmetrical overstressed zones. Resume: La centrale hydroelectrique de Siah Bishe est actuellement en construction. Les resultats des investigations, les analyses portant sur la stabilite des ouvrages ainsi que les etudes de soutènement sont decrit. La centrale est situee dans les roches sedimentaires et volcaniques permiennes. Le concept definitif de soutènement de la caverne est determine par les espaces et les epaisseurs des zones de cisaillement en couches Parallèles. Zusammenfassung: Das Pumpspeicherkraftwerk Siah Bishe wird zur Zeit gebaut. Die Untersuchungsergebnisse, die Standsicherheitsanalyse und der Sicherungsentwurf fuer die Kaverne werden beschrieben. Das Krafthaus liegt in Sediment- und vulkanischen Gesteinen des Perm. Die Abstande und die Dicke der schichtparallelen Scherzonen bestimmen die endgueltige sicherung. 1. INTRODUCTION Lahmeyer International was entrusted 1983 with the design of the 4 X 250 MW Siah-Bishe Pumped Storage Scheme. The waterways of the plant are now under construction (see fig. 1). It is located in the northern part of the Alburz Mountain, at a distance of 80 km from the Caspian Sea. The pumped storage plant is situated in layers of the Jurassic Shemshak formation and in the strata of Permian age called Ruteh, Nesen and Dorud formation. The Gamrudbar thrust fault separates the Jurassic Formation from the Permian one. This formation consists of shaly, slightly sandy siltstone, quartzitic sandstone and intrusions of igneous rock such as spilitic basalt partially bedding parallel orientated and massive Dacite. The whole formation is folded and forms the southern flanc of an anticline. The folding process caused a shearing of incompetent layers such as thin layers of siltstone between sandstone beds but also between siltstones with different content of fines like clay or fine sand. 2. INVESTIGATIONS The area of the underground powerhouse was investigated by the excavation of four test adits in total 700 metres long, by underground drillings of 1776 m, i.e. 31 boreholes with an average length of 57,6 m per hole. Figure 2 shows the arrangement of investigations. The boreholes were drilled in various directions and with different inclinations. Dilatometer tests as well as permeability tests have been performed in selected boreholes. The access adit with a length of about 310 m runs diagonally to the strike of the layers of the Dorud formation, mainly in massive limestones over the first 160 m, after that follow siltstones and sandstones and at the tunnel end Dacite is exposed. This exposed rock sequence has been geologically mapped, the discontinuities as joints and bedding planes have been evaluated and according to these results a portal was fixed for a cavern roof adit considering all other aspects such as lengths of tailrace tunnels, inclination of pressure shafts and the rock overburden above cavern roof. The excavated roof adit had a length of 196 metres. The first 50 m were inclined by 100 in order to reach the elevation of 1882 m which was 5 m below the cavern roof. 3. GEOLOGY OF THE CAVERNS 3.1 Bedding The roof adit exposed a rock sequence with a mean strike and dip of bedding planes of N 98°E/60°W up to station 120 m where a fault crossed the adit. The following rock sequence was striking parallel to the direction of the adit.
- North America > United States (0.28)
- Europe > Norway > Norwegian Sea (0.24)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.98)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.66)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Upper Marrat Formation (0.98)
- Asia > Middle East > Kuwait > Jahra Governorate > Arabian Basin > Widyan Basin > North Kuwait Jurassic (NKJ) Fields > Marrat Formation > Sargelu Formation (0.98)
ABSTRACT: Rock slope failures occur in marble quarries existing in the Anticline of Estremoz (Alentejo, Southeastern of Portugal). The main geological and geo-mechanical features of the discontinuities and of the marble rock material are presented. The description of some accidents which occured in three quarries (Cerca de Santo António; Estremoz; Encostinha II, Borba; Encostinha, Borba) was used to explain the mechanisms of failure involved in the rock slope failures of the marble walls. RÉSUME: Dans les carrières de marble qui existent dans I'anticlinal de Estremoz (Alentejo, Sud-Ouest du Portugal) il y a des glissements de masses rocheuses. Les caracteristiques geologiques et geomecaniques plus importantes des discontinuites et du rocher sont ici presentees. La description des accidents qui ont eu lieu dans trois carrières (Cerca de Santo António, Estremoz; Encostinha II, Borba; Encostinha, Borba) a permit d'expliquer les mecanismes de rupture concernes avec les glissements des parois de marbre. ZUSAMMENFASSUNG: Das Abrutschen von Felsmassen kommt in Marmorbruechen in dem Antiklinale von Estremoz (Alentejo, Suedöstliches Portugal)vor. Es werden die wichtigsten geologischen und geomechanischen Merkmale der Diskontinuitat und des Marmorfelsmaterials dargestellt. Anhand der Beschreibung einiger Unfalle, die sich in 3 Steinbruechen ereigneten (Cerca deSanto António, Estremoz; Encostinha II, Borba; Encostinha, Borba) werden die Spaltmechanismen erklart, die das Abrutschen der Marmorwande verursachten. 1. INTRODUCTION: Rock slope failures may occur in civil engineering works in mining and even in natural slopes. The most frequent are circular slidings, involving crushed and highly weathered rock, toppling, planar and wedge failures. To predict and to prevent these accidents it is required a convenient understanding of the mechanisms which are involved during the failure. Hence, it is appropriate to clearly define the geotechnical features of the rock mass (physical, geometrical, mechanical and hydraulical characteristics of the rock material and the discontinuities); and the characteristics of the accident (volume involved in the failure, the speed of the movement and the energy dissipated during sliding) and the factors which may explain it (weight and other loads, shear strength of the mobilized discontinuities, porewater pressure). Due to the mining conditions, several minor rock slope failures occur every year in the marble quarries which exist in the Anticline of Estremoz, Alentejo, the Southeastern region of Portugal (Fig. 1), and provide suitable information to study rock slidings. In this paper some of the major accidents are commented focusing the relevance of the features of the discontinuities which were involved and the mechanisms of failure which were observed. 2. THE MARBLE FORMATION: Several high quality varieties of marble are quarried, near the towns of Estremoz, Borba and Vila Viçosa. Most of the extracted material is used in the internal market, but a very high percentage of the production is exported as blocks, plates, or tiles for buildings and other civil engineering works abroad. The marble formation is part of the anticline of Estremoz, which is a rather heterogeneous geological structure extending for about 40 km and striking NWSE. Besides marble layers, it is mainly composed by dolomite (90 % of the existing outcrops), and by schists, calcoschists and metavulcanites. The quarries with such features - small area and big depth - exist due to several factors: the swallow topography does not create conditions for a hillside quarry like in Carrara, Italy; the geological structure of the anticline enables an exploration technique by using subvertical walls which follow the discontinuities set and preferably the bedding planes ("corrume"); at the surface most of the outcropping rock mass is weathered, fractured, and carsified, with a thick earth topsoil and the good quality rock material only tends to appear at certain depth.
- Geology > Structural Geology > Tectonics > Compressional Tectonics > Fold and Thrust Belt (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
Abstract: During the construction of the large caverns of the Rogun hydropower station in Tadzhikistan, large displacements in the upper part of the major cavern were observed. The caverns are situated in a rock mass consisting of up to 85% jointed sandstones with high initial stresses. The construction process has been interrupted by financial and political considerations. When the construction process can once again proceed, engineering solutions that will provide for the stability of cavern walls are needed. The back analysis system, designed to cope with changing geo-mechanical situations during construction and based on the computer code STATAS and stochastic as well as deterministic models of rock mass, is considered as an important tool to achieve this. Zusammenfassung: Beim Bau der groβen Kavernen des Rogun-Wasserkraftwerks in Tatschikistan wurden betrachtliche Verformungen der Kavernenwande festgestellt. Die Kavernen liegen zu mehr als 85% in dickbankigem, festem, geklueftetem Sandstein mit hohen Primarspannungen. Der Bau des Anlagenkomplexes ist gegenwartig aus finanziellen Gruenden unterbrochen. Fuer die Wiederaufnahme des Baus muessen die notwendigen Ingenieurlösungen zur Begrenzung der Gebirgsverformungen, sowie zur Konstruktion und Ausbruchstechnologie ueberarbeitet werden. In diesem Zusammehang wurde eine Reihe von Erst- und Rueckrechnungen unter Verwendung des FE-Programmsystems STATAS durchgefuehrt. Das verwendete Rueckrechnungsverfahren basiert auf einer Kombination aus stochastischen Modellen zur Verteilung der Kennwerte des Gebirges, Vergleichsbetrachtungen mitanderen Projekten mit Hilfe einer Datenbank und einer systematischen Variation der Steifigkeitseigenschaften des Gesteins, der Trennflacheneigenschaften und des Primarspannungszustandes. Resume: Pendant la construction des larges cavernes de la station hydro-electrique de Rogun dans le Tadzhikistan, de larges deplacements dans la partie superieure de la caverne principale ont ete observes. Les cavernes sont situees dnas une masse rocheuse composee jusqu'à 85 % de gres fissures avec des contraintes initiales elevees. Le processus de construction a ete interrompu à cause de considerations politiques et economiques. Quand le processus de construction pourra recommencer, des solutions d'ingenierie pour la stabilite des murs de la caverne seront requises. Le système d'analyse inverse, conçu pour les situations geomechaniques qui changent pendant la construction et base sur le code de calcul STATAS ainsi que sur des modèles stochastiques et deterministiques de la masse rocheuse, est considere comme un outil important pour cet achèvement. Experience and knowledge have, throughout the history of man, been gained by an analysis of past events, decisions and mistakes, either viewed from the sidelines or described by those who were active participants. Rock engineering is not an exception to this general process of human development; it is notably a discipline in which previous practice is the most secure basis for structural design and for the selection of excavation and support methods. Following generally adopted terminology, in this paper we will call "back analysis" the set of procedures which provide for the given period of time the best possible description of the geotechnical situation around the structure under construction/or already constructed. We will describe "back calculation" as the numerical procedure which enables the verification of an updated structure design with respect to modified rock mass parameters obtained during the back calculations. The whole set of such procedures during construction is usually termed as "monitoring". Considering possible procedures for back analysis, one should be aware of the principal limitations inherent in such approaches. First, the definition of the deformation parameters of rock mass based on the known displacements usually measured in situ even for the linearly elastic material is a nonlinear problem because there are more unknowns (Young's modulus, Poisson's ratio, stress) than constitutive equations. On the other hand, most rocks show distinct non-linear deformation behaviour. In direct calculations, there are no difficulties in accounting for known, non-linear properties of the given material.
- Europe > Russia (0.29)
- North America (0.28)
ABSTRACT: The paper deals with the specific failure potentials in tunnelling and underground work. By reviewing the experiences gained by excavating tunnels especially in difficult ground, it can be shown that most of the actual structural and functional failures are not covered by the usual engineering approach of analysing structural models. Therefore, engineers should develop rational means in addition and beyond those of numerical analyses. There is an urgent need for improved methods firstly to identify possible failures and secondly to apply adaquate risk assessments to these potential failures. RÉSUMÉ: L'article traite de possibilites de dommage specifiques pour des construction souterraines. Gràce aux experiences faites pendant des creusements, particulièrement dans les terrains difficiles, on peut montrer que la plupart des cas de dommage reels ne sont pas inclus dans les analyses conventionnelles des structures. A cóte des analyses numeriques il faut donc developper supplementaires. Il y a un besoin urgent des methodes ameliorees, qui donnent les moyens pour identifier les cas de dommage possibles et en plus qui fournissent des critères d'une estimation des risques dans ces cas. ZUSAMMENFASSUNG: Der Aufsatz befaβt sich mit den fuer den Bau unterirdischer Hohlraume spezifischen Schadensmöglichkeiten. Auf Grund der Erfahrungen, die beim Vortrieb, insbesondere bei schlechtem Baugrund, gewonnen wurden, kann gezeigt werden, daβ die meisten der realen Schadensfalle nicht durch die ueblichen Nachweisverfahren von Ingenieurbauwerken erfaβt werden. Daher sollten Ingenieure auch methodische Wege entwickeln, die ueber die numerischen Berechnungen hinausgehen und sie erganzen. Es besteht ein dringender Bedarf fuer verbesserte Methoden, die erstens mögliche Schadensfalle identifizieren und die zweitens fuer diese Falle Risiko-Assessments bereitstellen. 1 INTRODUCTION: We engineers are promising, well ahead before the structure or design is exposed to an actual test, that by applying our methods of design, analysis, and construction our engineering structure will fulfill its functional purpose and will neither fail nor causing damage. The design and the excavation of an underground work should be safe and economical during the projected life time of the structure as well as in all its construction phases. Engineering design, therefore, is concerned with avoiding failures, running no risks. Yet, running no risk at all is bad engineering, because of the higher costs and the missing innovations. Progress and risk-taking are inseparable. Moreover, excavating a tunnel in a hitherto unknown ground is always an innovation in the sense of constructing a prototype, mastering ever new situations. Good engineering, therefore, implies taking risks, yet knowing the potential hazards, and preventing failures nevertheless. By reviewing our experiences and pondering upon the actual engineering work of a specific tunnelling project, some questions may arise: What is our approach for finding all possible hazards and failure potentials? Rather intuitively: a sudden idea in a sleepless night? Or do we provide sufficient time for a systematic screening of the entire work to be done to find all hazards? Do we take - or have - time enough for exploring all the possible harzards, for weighing their damage potentials and putting them in an order of priority? Experiences prove that overlooking, just simply being unaware of a dangerous situation is the most critical case. In general we apply safety analyses only for those situations for which we have developed a tool for expressing safety by numbers. The design methods as given by codes and standards cover only structural failures, even not all the possible ones. Yet, what is our risk assessment approach for those hazards which defy any analytical evaluation? These questions can be raised, of course, for all kinds of engineering structures. However, they are especially relevant for tunnelling and underground works.
High Slope Stability In the Case of Improvement of the Mechanical Properties of the Rock Mass
Jasarevic, Ibrahim (Faculty of Civil Engineering, University of Zagreb) | Kovacevic, Meho-Sasa (Faculty of Civil Engineering, University of Zagreb) | Kulic, Z. (Faculty of Civil Engineering, University of Zagreb)
ABSTRACT: The rock massif strengthening using micro-reinforced shotcrete (MRS) with polypropylene fibers and prestressed bolts of high rigidity is presented in the paper. The results of carbonate rock complex classification and those obtained by geotechnical laboratory testing of rock samples and micro-reinforced shotcrete, including results of the in situ testing of the strengthened massif's mechanical properties are equally provided. A numerical analysis of a strengthened rock slope over 40 m in height and inclined to approx. 85° was also made and is presented in the paper. RESUME: L'amelioration d'un massif rocheux par beton projete micro-arme à fibres polypropylènes et par ancres precontraintes est presentee dans le present ouvrage. Les auteurs presentent les resultats de classification du complex carbonatique rocheux, les resultats des essais geotechniques en laboratoire effectues sur les echantillons du massif et sur le beton projete rnicro-arme, ainsi que les resultats de l'analyse des caracteristiques mecaniques du massif après amelioration. La simulation numerique du massif rocheux incline à environ 85° et de plus de 40 m d'hauteur a egalement ete effectuee. ZUSAMMENFASSUNG: Im Artikel wird eine Verbesserung des Gesteinmassivs mittels Spritzbeton, mikrobewehrt mit Polzpropzlenfasern, und vorgespannten steifen Ankern dargestellt. Prasentiert sind die Ergebnisse der Klassifikation des Karbonatgesteinkomplexes, der geotechnischen Laboruntersuchungen der Gestein- und Spritzbetonproben, sowie "in situ" Untersuchungen der mechanischen Eigenschaften des verbesserten Gesteinmassivs. Eine numerische Simulation des verstarkten Gesteinhangs mit Neigung von cca 85° und ueber 40 m Höhe wurde durchgefuehrt. 1. INTRODUCTION: The water required by the town of Rijeka has been taken from the water-pumping site Zvir since 1894. This site is presently the axis of the town's water supply system as it provides approx. 70% of all required water in the dry season. However, the capacities of the existing pumping station are limited and can no longer meet the growing water-supply needs of the town. In order to resolve this problem, a team of experts prepared in 1987 a study for the construction of a new pumping-station structure. At that, it was necessary to examine the stability of the water- pumping site, since a roof structure was initially built above the basin and the high and steep rock slope above the Zvir site in the Rječina canyon has on several occasions been "strengthened" by concrete. Several attempts have been made over the last hundred years to ensure the local and, to some extent, the global stability of the slope. However, the local and global stability of the slope still remained inadequate and, for that reason, the main design involving the reinforced-concrete grid composed of horizontal and vertical girders was prepared in 1988. Due to the great quantity of the work and material required to build the grid structure (table 1), it was finally decided to adopt the system of rigid prestressed bolts with reinforced concrete bolt heads which fit harmoniously into the natural environment. In addition, the new design elements are much more rational than those proposed in the previous solution (table 1). 2. ENGINEERING GEOLOGICAL DATA: The slope above the Zvir pumping station is mainly composed of the well bedded Upper Cretaceous limestones and dolomites. The dolomite occurrences have been registered in the retaining wall zone (macroblock I). The Zvir water-bearing site was formed in the tectonically very mobile area where the carbonate mass moves with a relative ease along the plastic surface (mainly composed of flysch). Small changes in pressure directions are sufficient to cause cracking and rotation of macroblocks, so that reverse faults, sometimes of considerable size, are formed in boundary zones. The rotated tectonic blocks become deformed and finally crack thus forming variously fissured and oriented microblocks.
- Geology > Structural Geology (1.00)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Dolomite (0.45)
Abstract: This paper examines a range of engineering solutions for crossing unstable and potentially unstable colluvium and talus slopes near the village of Kizlac, in the Nurdag Ranges of Southern Turkey. The paper is a companion paper to that written by Smith Brunsden Searle (1993), describing a number of potentially unstable areas over a four kilometre stretch of the Horu River, including a mudslide and other talus and colluvium slopes requiring special engineering solutions. Reasons for the selection of the most suitable route are presented, together with reasons for the rejection of alternat1ve routes. For the chosen route, the detailed engineering solutions cover the construction of piled and anchored walls to support a motorway, together with drainage and talus control measures. Details of the parameters used in the design of structures are presented and the advantages and disadvantages of the various options examined, both from a technical and cost viewpoint. Resume: Ce papier exasine une variete de solutions ingenieurs pour depasser des instables et potentiellement instables pentes de colluvium et de talus à Nurdag au sud Turque. Ce papier est relie avec le papier ecrit par Smith Brunsden Searle (1993) et qui decrit un nombre de regions potentiellement instables de boue glissant et d'autres pentes de talus et de colluvium qui demandent specialles solutions ingenieures. Les raisons pour lesquelles on a choisie Ie chemin Ie plus convenant sont presentees. Pour la route choisie les details des solutions ingenieures qui couvrent la construction des rideaux et des palplanches d'ancrages pour supporter l'autoroute et les mesures de control de draine et du talus sont presentees. Les details de caculs les avantages et les desanvantages des differents choix. Zussamenfassung: Die vorliegende Abeit beschreibt eine Anzahl von technischen Lösungen fuer den Baueiner Straβenstrasse durch ein Gebiet sit instabilem und potentiell instabiles Kolluvius sowie von mit Schuttkegeln bedeckten Hangen in der Umgebung des Dorfes Kizlac, Nurdag Gebirge (suedliche Tuerkei). Diese Arbeit erganzt den Beitrag von Smith Brunsden und Searle (1993), die eine Anzahl von instabilen Gebieten entlang eines 4 ks langen Abschnittes des Flusses Horn beschreiben. Auf dieser Strecke befinden sich ein Erdrutsch sowie Hange mit Instabilen Schuttkegeln und Kolluvium, die spezielle bautechnische Aufserksamkeit erfordern. Die vorliegende Arbeit diskutiert die Auswahl des guenstigsten Trassenverlaufes und bibt Gruende fuer die Zurueckweisung von Alternativlösungen. Die bauchliche Verwirklichung der Trasse erfordert die Konstruktion von tiefgruendigen, verankerten Elesentwanden, Maβnahmen zur Drainung und Meβstellen zur Beobachtung der Hangbewegung. Die fuer die Planung verwendeten geotechnischen Kennwerte werden erlautert. Vor-und Nachteile der verschiedenen Alternativen werden unter dem Aspekt ihrer technischen Durchfuehrbarkeit und ihrer Kosten diskutiert. 1 INTRODUCTION: The area described in the companion paper by Smith Brunsden and Searle (1993) is one of intense tectonic activity in which the metamorphic rock (mica/hematite/chlorite schist, phyllite and meta quartzites) has been folded and faulted with the subsequent development of many unstable or semi-stable areas. The types of potential and active slides, their properties and methods of analysis, have been described and illustrated in Figures 1 to 4 in the companion paper, so that the figure numbers here commence at Figure 5. In essence the area has large relic slides such as the Kizlac mudslide and smaller talus slopes. The mud-slide has a track lengths of 850m and involves a mass of some 14 million cubic metres of material. The talus slopes, have active talus at higher elevations and colluvium lower down, with the thickness of these materials increasing very rapidly downslope. In the mudslide, the depth of slide debris is almost constant and a pronounced, shear zone exists, including both blocks of rock and gouge materials.
- Geology > Rock Type > Metamorphic Rock (0.53)
- Geology > Structural Geology > Tectonics (0.50)
ABSTRACT: The main concepts underlying the application of modelling to the assessment of structural behaviour are examined. Criteria for safety and performance evaluation, modelling assumptions, analysis techniques and validation procedures are discussed. The papers submitted to this theme are briefly reviewed, stressing the major contributions. RÉSUMÉ: On examine les concepts principaux subjacents à l'application de la modelisation au jugement du comportement structural. On discute les critères pour l'evaluation de la securite et performance, les hipothèses de la modelisation, les techniques d'analyse et les procedes de validation. Les communications soumises a ce thème sont brièvernent passees en revue, en accentuant les contributions majeures. ZUSAMMENFASSUNG: Die wichtigsten, der Anwendung der Modellierung fuer die Bewertung des strukturellen Verhaltens zugrundeliegenden Begriffe werden untersucht. Kriterien fur die Sicherheits- und Ausfuehrungsabschatzung, Modellierungsannahmen, Techniken fuer die Analyse, und Verfahren zur Gueltigkeitsbestatigung werden diskutiert. Die zu diesem Thema eingereichten Referate werden kurz besprochen, unter Betonung der Hauptbeitrage. 1 INTRODUCTION: Rock Engineering concerns a broad field of activities, such as those related to civil, mining and petroleum engineering, as well as to the earth sciences (Rocha 1983). The economic development and the improvement of the quality of life have led to interventions in the environment of unprecedented dimensions, such as those in the fields of the land and marine environment (geology and geotechnology, marine geology, natural hazards, earthquakes), of the natural resources (dams, reservoirs, mines), and of the transportation networks (roads, bridges, etc.). Rock masses support structures (foundations, slopes, tunnels, wells and caverns). The object of rock engineering is therefore the planning, design, construction, maintenance and rehabilitation of the above indicated structures. Owing to their nature, and to the presence of joints and faults, rock masses are generally heterogeneous and discontinuous media, with complex, anisotropic, non-linear behaviour. Furthermore, the processes of their formation and alteration in time led to installation of complex states of strain and stress. Rock engineering should therefore be viewed within the framework of the relations between Man and environment. When intervening in the environment with the purpose of developing, modifying or protecting it, the engineer starts, in a first phase, by monitoring the environmental variables which may be of interest. A modelling phase will follow, in which the engineer develops the models for the interpretation of the monitoring results and for evaluation of the planned intervention. The design of the intervention is the third phase, and finally the implementation of the intervention is the fourth phase. As each intervention modifies the environment, to start a new intervention we should return to the first phase, i.e., to the monitoring of the modified environment. This cycle thus continues indefinitely (Oliveira & Pedro 1992, 1993). Modelling in rock engineering is therefore an important phase in the cycle of the intervention in the environment, which essentially provides support for monitoring and design activities. Both these activities require the assessment of the structures behaviour either to control their operation or to evaluate the design solutions. The assessment of the behaviour of the structures in rock masses is supported by appropriate criteria, models and methods of analysis. In recent decades, however, important steps have been made towards the separation of concepts concerning the criteria, models and methods of analysis, as well as towards the unification of those concepts for the different types of structures (Borges & Castanheta 1983, Rocha 1978, ICOLD 1984, 1987, 1993). In the following sections of this report the scope of the theme will be defined, the papers presented will be briefly reviewed, and some questions which seem to deserve further discussion will be selected.
- North America > United States (0.47)
- Europe > Portugal (0.29)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type (0.68)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.55)