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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: 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 stability of underground structures is the most important and complicated concept in rock engineering. There is no explicit way to evaluate the stability of a structure in rock. For this reason implicit methods accounting for the stability through exploration and analysis of rock mass structure are discussed. This includes properties of the rock mass, support measures and excavation/construction technology, possible modes of structural behaviour and accumulating experience and engineering judgment. The significance of in situ measurements, rock mass and structure monitoring and back analysis is also emphasized. Resume: La stabilite de constructions souterraines est Ie concept Ie plus important et complique en ingenierie de la roche. II n'ya pas de manière explicite pour evaluer la stabilite d'une construction dans la roche. Pour cette raison, ce rapport discute des methodes implicites qui tiennent en compte de la stabilite par l'exploration et l'analyse de la structure de la masse rocheuse. Ceci inclut les proprietes de la roche, les mesures de soutènement et la technologie de l'excavation/construction, l'operation des modes possibles de construction et l'experience accumulee et Ie jugement de l'ingenieur. La signification des mesures in situ, la surveillance de la masse rocheuse et de la construction et l'analyse inverse sont aussi soulingnees. Zusammenfassung: Die Stabilitat unterirdischer Felsbauten ist das wichtigste und schwierigste Konzept innerhalb des Felsbaus. Es gibt keine direkte Methode, urn die Stabilitat von unterirdischen Felsbauten zu bestimmen. Aus diesem Grund werden implizite Methoden diskutiert, welche Voruntersuchungen und Analysen des Felsbauwerkes umfassen. Diese beinhalten Felseigenschaften, Verstarkungsmaβnahmen, Ausschachtungs- und Baumethoden, unterschiedliche Betriebsverfahren, gesammelte Erfahrungen und technisches Verstandnis. Auf die Bedeutung von in situ Messungen, Zustandsueberwachung des Felsens und des Bauwerkes und Rueckrechnungen wird ebenfalls eingegangen. 1 INTRODUCTION: The stability of underground structures is the most important and complicated concept in rock engineering. There is no explicit way to evaluate the stability of a structure in rock. Referring to the preamble above, it can be said that our knowledge of this matter is really limited. The structure may be considered stable at a given point in time, but fail to comply with a required mode of operation shortly afterwards due to the loss of stability. So, when we speak about the stability of an underground structure, we usually have in mind either prediction of stability for some period of time, or physical evidence of its existence at a given moment as a source for further predictions. In this respect, the best we can do is to refer to the concept of stability in terms of time and probability. Some uncertainty exists in the definition of the concept itself: stability may be understood as a local feature when failure of some structural elements does not lead to the cave-in of the structure as a whole; or as an overall attribute opposite to complete collapse. There are many natural openings in rock which have been stable for thousands of years, and manmade underground structures which have remained stable for centuries, i.e., for time periods which, in recent engineering practice, relate to caverns for underground radioactive waste disposal facilities. The last decades of monitored performances have provided us with many valuable experiences of the creation of underground structures in rock for mining and construction activities. Almost fifty papers were submitted and accepted for Theme 3 of this Symposium. One is actually related to soil mechanics and not rock mechanics, but otherwise adds to our understanding of the concept of stability. The authors of the papers included in the Proceedings of the Symposium will be referenced herein by the name(s) only. All other publications will be referenced in accordance with normally adopted procedure, including date.
- Asia (0.46)
- Europe > Russia (0.28)
- North America > United States (0.28)
- Water & Waste Management > Solid Waste Management (1.00)
- Energy > Power Industry > Utilities (0.34)
ABSTRACT: Tokyo Electric Power Co. (TEPCO) has been constructing the Sabigawa pumped storage power plant with an output of 900 MW since 1986. In order to develop a more efficient system for measuring the expansion of a loosened zone caused by the excavation of a cavern for the underground power plant (29m wide. 51m high, and 165m long), TEPCO tested various kinds of new in-situ measuring methods, such as a method measuring rock stress changes around the cavern, and a method measuring acoustic emission propagated through the rocks, in addition to an interval strain measuring method using the conventional multi-channel extensometer. The measured results proved some new measuring methods to be effective for practical use. RÉSUMÉ: Depuis 1986, la societe Tokyo Electric Power Co. (TEPCO) construit la centrale electrique d'accumulation par pompage de Sabigawa d'une capacite de 900 MW. En vue de developper un système de mesure plus efficace de l'expansion dans la zone desagregee causee par l'excavation de la cavite pour une centrale electrique souterraine (largeur: 29m. hauteur: 51m, longueur: 165m), TEPCO a effectue des essais portant sur diverses nouvelles methodes de mesure sur le terrain, comme par exemple une methode de mesure les modifications des contraintes internes de la roche autour de la cavite, une methode mesurant l'emission acoustique propagee à travers la ruche, en plus d'une methode de mesure des contraintes par intervalle utilisant l'extensomètre (jauge de contrainte) conventionnel à canaux multiples. ZUSAMMENFASSUNG: Die Firma "Tokyo Electric Power Co." (TEPCO) baut seit 1986 das pumpenspeicherungs-Kraftwerk Sabigawa mit einer Leistung von 900 MW. Zur Entwicklung eines leistungsfahigeren Systems zur messung der durch die Ausschachtung eines unterirdischen Hohlraums far das unterirdische Kraftwerk (29m breit, 51m hoch und 165m lang) verursachten Erweiterung einer aufgelockerten Zone, hat TEPCO verschiedene Arten von neuen in-situ Meβverfahren getestet, wie einem Verfahren zum Messen von Veranderungen der Spannung im Felsen ringsum den unterirdischen Hohlraum, einem verfahren zum Messen der durch den Felsen propagierten akustischen Emission, zusatzlich zu einem Verfahren zum Messen der Spannung in Abstanden unter Verwendung des herkömmlichen Mehrkanal-Dehungsmessers. Die Meβergebnisse haben gezeigt, daβ einige neue Meβverfarhen fuer pratische Anwendung leistungsfahig sind. 1 INTRODUCTION: The underground power plant is located at A depth of about 200m from the ground surface and designed to house three sets of 300- MW hydraulic turbine generators and three sets of 335-MVA transformers in the same cavern having a large cross-sectional area of about 1,500m. Bench-cut excavation was successively carried out from bench No.1 to bench No.14 (each bench has a bench height of 2.5m) from the top arch section to the bottom of the cavern. The geology in and around the cavern is heterogeneous and discontinuous, and consists mainly of various kinds of rhyolites containing fracture zones and planes, in addition to well developed joints. At the time of starting the excavation, the geological condition in and around the cavern to be excavated was investigated in detail and, a large number of various measuring instruments were set around the cavern. The measured results with the instruments were processed and analyzed in real time by means of an EWS (engineering work station) installed at the site office. In addition, in order to make the design more efficient and improve the safety, a so-called observational method system was developed and introduced for predicting the rock behavior in and around the cavern at the next stage of bench-cut excavation on the basis of the processed and analyzed results of the measurements. Since it was considered to be important to establish a standard of judgment for confirming the stability of the cavern.
How can we rock mechanics and rock engineers contribute to the development of a better environment and better use of our finite and renewable resources? These were questions many of us asked ourselves before arriving to this Symposium and the wonderful city of Lisbon. After four days of intense program where we have been listening to keynote lectures, general reports of written contributions, presentations of individual papers, workshops, and lively discussions we are convinced that we have important safety and environmental issues to assess to the society. The general environmental issues have been i focus for quite some time now, but it is obvious that they start to enter more and more our specialisation. As we meet for the first time at an international symposium that is specially addressing the environmental and safety issues in rock mechanics we are in a stage of transition. We have been listening to contributions that can be looked upon as traditional rock mechanics but they fit in to the overall scope of the Symposium. The contributors are well aware of the environmental issues and they like to demonstrate how rock engineering contributes to the safety and environmental issues. The other group of contributions are those addressing new environmental issues to rock engineering. To illustrate this statement two examples from the written keynote lectures to the Symposium will be used. The paper by Hönisch about "Conclusions drawn from 100 constructed power caverns for future planning" gives design experience and design rules from constructed power caverns from various parts of the world. The compilation of data could have been presented at any rock engineering conference but Hönisch extracted the interesting data about safety and environmental issues and presented to us. As an example of a direct application of rock engineering to environmental issues I would like to refer to the study" Tunneling under an industrial waste landfill in Italy: Environmental controls and excavation procedure" by G. Barla and P. Jarre. The authors demonstrated the environmental impact and assessments to a rock engineering construction and the contribution illustrated the strong need for a better and deeper knowledge in rock chemistry as we start to tackle this kind of problems. The 1993 ISRM International Symposium on Safety and Environmental Issues in Rock Engineering consisted of four themes:Modelling in Safety Evaluation Influence of the Environment in Rock Engineering Stability of Large Underground Structures Contribution of Failures and Incidents to theProgress of Rock Engineering Modelling in Safety Evaluation To demonstrate to the public the long-time safety, stability and performance of rock engineering structures we need the tool of mathematical modelling. At the first theme of the Symposium only 4 contributions of totally 32 were dealing with modelling for safety evaluation. Seven contributions were addressing the important aspects of verification and validation of computer codes for rock engineering applications. In the field of verification and validation of numerical techniques and computer codes we can learn from the hydrologists and hydrogeologists.
- Law > Environmental Law (1.00)
- Energy > Oil & Gas > Upstream (0.48)
ABSTRACT: Rock parameters and support details for power caverns are compared with earlier recommendations for tunnel support using rock mass quality indices. New diagrams are proposed for cavern wall support. Estimates of economical cavern sizes and admissible rock stresses are discussed on the a.m. basis. Observed cavern deformations and recommended grids for monitoring installations are presented. RESUME: Les paramètres des roches ainsi que les dispositifs de soutènement de centrales souterraines preconises sont compares à des recommandations anterieures ayant trait au soutènement de tunnels et utilisant des indices sur la qualite des masses rocheuses. De nouveaux diagrammes afferents au soutènement des parois des cavernes sont proposes. Des estimations sur les dimensions economiques des cavernes ainsi que sur les tensions rocheuses sont analysees de manière analogue. Les deformations des cavernes observees et les espaces recommandes entre les instruments de mesure sont egalement mentionnes. ZUSAMMENFASSUNG: Felsparameter und Sicherungsvorschlage fuer Krafthauskavernen werden mit frueheren Empfehlungen fuer den Tunnelausbau verglichen, die Felsqualitatsindizes benutzen, Neue Diagramme werden fuer den Ausbau der Kavernenwande vorgeschlagen. Auf der gleichen Basis werden Schatzungen fuer wirtschaftliche Kavernenabmessungen und zulassige Gebirgsspannungen diskutiert. Beobachtete Kavernenverformungen und empfohlene Abstande von Meβeinrichtungen werden angegeben. 1. INTRODUCTION: The design of powerhouse caverns requires extensive efforts for investigation, stability analysis and construction monitoring which will only be exceeded by design of underground waste storage caverns. The stepwise design process shows the requirement for strongly increasing reliability of parameter evaluations with growing chances of realization. The presented approach is expected to be useful at least for earlier design stages and to be confirmed in later design stages:Intact rock parameters can be modified to rock mass parameters after careful evaluation of joint persistence and spacing in detailed mappings of investigation admits. Rock mass classification can be used to decide on the economy of planned cavern size, on the possible construction under given in situ stresses and the admissible deformations of the cavern contour. Previous examples of cavern support can be considered before numerical modelling of excavation and support. The work described was conducted from a consultant's point of view. Some simplifications which may seem too crude for research purposes were inevitable. This approach was largely influenced by the report of BARTON et al. (2,1980) and the report of KAISER (9,1986) in which the construction risks for caverns were estimated by means of rock quality indices. The safety and economy of cavern construction can be significantly improved by appropriate modelling of the rock mass behaviour and investigating necessary support upgrading due to parameter changes well in advance of actual construction. Great importance has to be paid to trigger values of partial and total deformations of cavern excavation contours. This requires stepwise modelling of excavation and reliable monitoring of later representative rock deformations. Sometimes, inadequate investigations in earlier design phases have limited availability of rock mass parameters and prohibited stability analyses and the possible design input that can be gained from them. Necessary design decisions have then been postponed which has caused even more time consuming design changes and contract negotiations at a later date. A procedure is presented herein for using empirical support design rules based on simple modelling of rock mass behaviour and based on published and unpublished experience of the design and construction of existing power caverns. Evaluation and comparison of rock mass classification results are based on references 1 and 3. The classification was performed for 100 power caverns and the title for this paper was chosen accordingly.
- Europe (1.00)
- North America > United States (0.28)
Applications of Computational Mechanics to Underground Hydroelectric Schemes
Sousa, L.R. (LNEC - Laboratorio Nacional de Engenharia Civil, Lisbon) | Lamas, L.N. (LNEC - Laboratorio Nacional de Engenharia Civil, Lisbon) | Almeida E Sousa, J. (FCTUC - Faculdade de Ciencias e Tecnologia, University of Coimbra)
ABSTRACT: An analysis of the calculation methodologies followed in the structural design of underground structures in hydroelectric projects is presented, as well as the numerical models usually adopted. Some applications of computational mechanics to the Alto Lindoso hydroelectric power scheme, in Portugal, are presented. Numerical models were developed for the underground powerhouse complex and for the surge chamber. A comparison between the predicted values from the numerical solutions is made in order to permit a continuous safety evaluation of the underground structures. RÉSUMÉ: Une analyse des methodes de calcul utilisees dans la conception structurale des structures souterraines dans des projets hydro-electriques est presentee, ainsi que des modeles numeriques habituellement adoptes. Quelques applications de la mecanique computationnelle au projet hydro-electrique du Alto Lindoso, au Portugal, sont presentees. II a ete developpe des modèles numeriques pour le complexe de la usine souterraine et pour la cheminee d'equilibre. La comparaison entre les valeurs prevues pour les solutions numeriques est effectuee à fin de permettre une evaluation de securite continue des structures souterraines. ZUSAMMENFASSUNG: Es werden die Berechnungsverfahren, die zur Erstellung des strukturellen Entwurfs von unterirdischen Strukturen bei hydroelektrischen Projekten verwendet werden, dargestellt, sowie die numerischen Modelle, die dabei gewöhnlich verwendet werden. Im folgenden werden einige Anwendungen von Computermechanik im Bezug auf das hydroelektrische Kraftwerk in Alto Lindoso/Portugal erlautert. Zur Analyse der verschiedenen Bauphasen wurden numerische Modelle fuer das unterirdische Kraftwerkshaus und das Wasserschloβ entwickelt. Um eine kontinuierliche Bewertung der Sicherheit der unterirdischen Strukturen zu erhalten, werden die tatsachlichen Werte mit denen, die von den numerischen Lösungen vorausgesagt wurden, verglichen. 1 INTRODUCTION Considerations are made about the conception and calculation methodologies followed in the structural design of underground structures in hydroelectric projects, as well as about the computational methods usually adopted for predicting the structural behaviour and quantifying actions. Some applications of computational mechanics to the Alto Lindoso hydroelectric power scheme, in Portugal, are presented. Special emphasis is made to a 3-D finite element numerical system suitable for the analysis of underground structures. The numerical models were developed for the underground powerhouse complex and for the surge chamber for the analysis of the different construction sequences. A comparison between observed and predicted values from numerical solutions is made in order to permit a continuous safety evaluation of the underground structures. Also a 3-D boundary element model was used in the determination of the most probable in situ state of stress in the rock mass. 2 CONCEPTION AND CALCULATION OF UNDERGROUND STRUCTURES 2.1 Preliminary considerations The use of the underground space for hydroelectric power schemes has been widely implemented where adequate conditions exist, because of the advantages that it brings when compared with surface solutions. The costs with the excavations and supports are usually balanced with the costs of the foundation and superstructure of surface powerhouses. In good rock masses, the supports of the tunnels, caverns and shafts can be considerably reduced or even eliminated, which can result in more economical solutions. Furthermore, the expropriation costs are reduced, and smaller economical and environmental impacts are originated. On the other hand, significant advances in underground technology and in computational methods have allowed an increasingly rational approach to the design of these underground structures. In these projects, several types of underground openings exist: the powerhouse complex, high and low pressure tunnels and shafts, surge chambers, and adits. Several possible types of arrangements exist for the hydraulic circuit. A very good example of the complexity of these projects is given by the Alto Lindoso power scheme, in the north of Portugal (Figure 1).
- Energy > Renewable > Hydroelectric (1.00)
- Energy > Power Industry (1.00)
ABSTRACT: In 1989 Neste Gas prepared a survey on different ways to store natural gas, which resulted m a job to plan a deep unlined hard rock storage for natural gas with an active volume of 100 million m. Field work in Mantsala (60 km north of Helsinki) consisted of geological and geophysical surveys followed by diamond drilling, drill hole seismics and rock stress measurements. A way to diminish the volume of gas was to chill it down to temperatures of about - 60°C. This required measurements of rock material characteristics down to that temperature to allow for stability calculations of the frozen rock mass. The standard strength and deformation characteristics (compressive strength, tensile strength, Young's modulus, Poisson's ratio) of the Mantsala gabbro were measured down to - 60°C. The results are compared to earlier frozen rock characteristics in the literature. ZUSAMMENFASSUNG: ln 1989 ausarbeitete Neste Gas eine Studie ueber verschiedenen Wei sen Erdgas zu lagem, die zu einem Beschaftigung fuehrte, einen unbekleideten Erdgastieflager in harten Gesteinen mit einem Aktivvolumen von 100 MiIIionen m zu projektieren. Die Feldarbeiten in Mantsala(60 Km nord von Helsinki) entfassten geologische und geophysikalische Studien gefolgt mit Diamantbohrungen, Bohrlochseismik und Bergspannungsmessungen. Eine Weise das Gasvolumen zu vermindem war es zu abkuehlen bis Temperaturen von - 60°C. Diese forderte Messungen der Felsmaterialseigenschaften bis diesen Temperaturen, die Stabilitatsberechnungen des gefrorenen Gebirges môglich zu machen. Die normalen Festigkeits- und verformungseigenschaften (Druckfestigkeit, Tragfestigkeit, Elastizitatsmodul, poisson's Verhaltnis) der Mantsala Gabbro wurden bis - 60°C gemesst. Die Resultaten werden mit frueheren Eigenschaften des gefrorenen Gebirges im Litteratur vergleicht. RÉSUMÉ: En 1989 Neste Gas preparait une analyse sur les moyens differents de stocker le gaz naturel, qui aboutissait au travail de la planification d'une cavite non revêtue profonde en roche dure pour le gaz naturel avec un volume actif de 100 million m. Le travail de gisement à Mantsala (60 km au nord d'Helsinki) se composait des recherches geologiques et geophysiques suivies par le forage de diamente, les etudes sismiques du trou fore et les mesurages des contraintes de la roche. Un moyen de diminuer le volume de gaz etait de le refroidir jusqu'à les temperatures d'environ −60°C. Cela exigait les mesurages des caracteristiques du materiel rocheux jusqu' à cette temperature pour rendre possible les calculs de stabilite de la masse rocheuse refroidie. Les resistances et les caracteristiques de deformabilite (resistance à la compression, resistance à la traction, coefficient d' elasticite, coefficient de poisson) du gabbro de Mantsala etait mesurees jusqu'à −60 °C. Les resultats sent compares avec les caracteristiques anterieures de roches refroidies dans la litterature. 1 NATURAL GAS IN FINLAND Natural gas has been imported to Finland from Soviet Union since 1974. Ten years the annual usage was about I billion m. Then gas was mainly used by pulp and paper industry. Nowadays more and more gas has been utilised for district heating and electricity production. In 1992 natural gas covered about 8 % of the energy supply of the country with a gas consumption of about 3 billion m (+20°C). Locally, in south-eastern Finland, it has a more than 30 % share in energy production (Fig.1). The distribution network now reaches the most important cities on the south-southeastern part of Finland. Its extension to the west coast together with a possible second supply line from Norway through Sweden is discussed as well as a connection to the Baltic gas network through Tallinn. 1.1 Storage needs The Finnish consumption of natural gas varies in cycles of different length. The most important of these are the daily and the annual variation.
ABSTRACT: Analyzed herein are the engineering-geological conditions within the area of the Tehri HPP underground structures which have been designed at the "Hydroproject" Institute. Complicated natural conditions, including high regional seismicity, required a complex of up-to-date geo-mechanical and geophysical studies and computational analyses to be performed providing the basis for elaboration of layout and design of power house and transformer hall. Particular attention in the paper has been given to the criteria of strength and stability of the rock mass surrounding the underground structures. 1 INTRODUCTION: Trustworthiness of safety prediction for such large underground ca- caverns in rock masses as HPP machine halls is a multi-factor function. Of greatest importance, in our opinion, are those listed below:adequate information about the properties of the surrounding rock mass. properly selected mathematical model for analysis of strain-stress state (SSS) and stability of the rock mass; validity of the reliability criteria applied. At present, tens of large HPP and been underground machine halls have been constructed all over the world; various methodologies and reliability criteria were used in designing thereof. Complexity, often unique characteristics of the structure as well as a great diversity of natural and engineering-geological conditions for the would-be and already constructed structures still pose new problems for the designers and scientists. Recent trends are towards decrease in the scope of pre-design surveys of site investigations at the areas underground structures and the primary emphasis is placed upon the surveys, in-situ observations and tests just in the progress of excavation which provide the basis for revision of excavation procedures and constructions. Such approach proved to be good in practice and made it possible to shorten the construction period and save funds. However, the inadequate scope of surveys at the designing stage can raise difficulties in the course of construction (as it took place at the construction of underground Fortuna HPP in Panama) and in the long run - in wasting time and money. Therefore, it is of great importance to specify the proper scope of surveys and site investigations, which would allow serious mistakes to be eliminated; decision of the problem is a kind of art. As results from the analyses of the publications of International Symposiums and Conferences, the finite element method (FEM) as applied to elastic-plastic stage has been mostly practised in studying the SSS of large underground caverns. As a rule, solution of two-dimensional problem, Mohr-Coulomb criterion of plastic flow and, in the latest years, Hooke-Brown criterion were applied. Criteria of reliability of large underground excavations are mostly complicated and ambiguous. There are some proposals to take some certain values of relative deformation or rock mass deformation velocity in the cours of excavation as the reliability criterion (Deere, Isaza, Ferro & Giussani 1986). But these criteria can be applied only for limited categories of rocks and cannot be considered as general ones. Often the reliability of an excavated cavern is considered as a function of sizes of plastic zones (zones of ultimate SSS) surrounding the cavern. In some other papers this factor is ignored, and interfacing of plastic zones in the area between the machine hall and transformer halls is allowed, and rock bolts are fully installed in the plastic zone. Considered below are the issues associated with study and validation of reliability of machine and transformer halls caverns at the Tehri HPP (India), designed at the "Hydroproject" Institute (Moscow, Russia).
- Asia (0.69)
- Europe > Russia > Central Federal District > Moscow Oblast > Moscow (0.26)