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Much of the research on fracture of rocks or rock-like materials
conducted over the past two decades may be considered as "academic
studies" of the general phenomenon of fracture. Yet, the
understanding of this phenomenon is fundamental if a material is
used in any engineering design, whether the aim is to prevent
failure of the structure or to promote it. Fracture theories
existing are generally empirical and derived from experimental
results of laboratory test with simple boundary conditions. Because
of the basic weakness of rock intension and because in general the
environmental stresses in rock mechanics are compressive most of
these theories consider fracture under compressive stress
conditions. The Coulomb-Navier-, the Mohr-, the Griffith and the
McClintock and Walsh criteria are typical examples and will be
considered in the following. In addition the tendency during the
past was in making accurate experiments under conditions of
homogeneous stresses. To obtain information about the fracture
behaviour with unequal principal stresses systems have to be used
which involve inhomogeneous stresses. This case is of particular
interest, since in practical rock mechanics we may expect
conditions of highly inhomogeneous stresses. However, a
consideration of such situations involve additional assumptions
like the applicability of the theory of elasticity for calculating
the stress field, which may be open to question. A distinction has
to be made between fracture initiation and fracture propagation,
since a detailed observation of the total fracture process in rock
was possible by means of "stiff" and "servo-controlled" loading
systems.
An important objective of the civil and mining engineer concerned
with structures in rock such as tunnels, open pits, dam foundations
and so forth is the creation of a safe and efficient design. This
necessitates an estimate of the immediate and long-term performance
of the surface or subsurface opening or foundation, whichever the
case may be. This in turn requires a quantitative estimate of those
physical and mechanical properties of the rock mass which govern
its strength, permeability and deformation charac- teristics. To a
lesser or greater extent, depending upon the type of engineer- ing
structure considered, these properties are a function of the 1)
attitude, 2) geometry and 3) spatial distribution of the joints and
other discontinuities in the mass. All three factors can be
determined, since the joints are detect- able features whose
characteristics can be quantitatively measured and described.
Joints are universally present in rock masses and have strength,
per- meability and deformational characteristics appreciably
different from those of the intact rock. Depending upon the origin
of the joints sets, their characteristics can vary greatly. Not
only can the average spacing between joints vary within wide
limits, but the nature and degree of joint infilling material,
physical characteristics of their planes and their degree of
develop- ment can be vastly different. Because of variations in
these properties one joint set can have very different effects than
another on, for example, shear characteristics. Hence, each joint
set should be examined individually for its properties.
Bei der Durchfiihrung der Bauarbeiten fiir den Ausbruch des
Hauptstrangs 2 der Zuleitungen Ost des Pumpspeicherwerks
Hongrin-Uman ,3 ergaben sich in ihrem AusmaJ3 nicht vorhergesehene
Schwierigkeiten. Dieser Stollen miindet prak- tisch am Ende des
Staues (hochster Stauspiegel 1255,00 m) auf Kote 1250,00 m, im Tal
des Hongrinbaches Paquier-Clavel in das Speicherbecken. Es handelt
sich urn 2 einen Freispiegelstollen iiblicher Form, Querschnitt 5
bis 8 m , Langsgefalle 3 %0. Aus der Gesamtanordnung des
Stollensystems ergab sich die Notwendigkeit, den Hauptstrang durch
das Massif des Mont d'Or zu fiihren (Abb. 1 und 2). Der ,N BASSIN
O*"CCUMUlAlION HONGRIN /~ Fain. ,00 0 500 1000" ~ .,f
"'j';';;!;iil!~!I~I!;lilt~~:/:~ ?::::::::: :*"'~~~A" Abb. 1. Chaine
du Mont-d'Or - Lageplan der Zuleitungen Ost (nach J. Nor be r t,
Geologe, Lausanne) Dichter Fels: 1 Tonschiefer mit Kalksandstein; 2
Anhydrit und Gips. Durchlassiger Fels: 3 zermalmte Rauhwacke; 4
stark zerkliifteter Dolomit und Dolomitenkalk; 5 zerkliifteter
Kalkstein Chaine du Mont d'Or - Plan of galleries, East adduction
Non water-bearing rock: 1 Clayey schist with sandy-limestone; 2
Anhydrite and gypsum. Water-bearing rock: 3 "Cornieules" (crushed
yellow honeycomb dolomite); 4 Dolomitic limestone and badly
fractured dolomite; 5 Fissured limestone Chaine du Mont d'Or -
Situation des adductions Est Roches etanches: 1 Schiste argileux it
niveaux greso-calcaires (flysch); 2 Anhydrite et gypse.
Auf Anregung einiger jiingerer Kollegen fand im AnschluB an das
Ludwig- Foppl-Kolloquium der Osterreichischen Gesellschaft fUr
Geomechanik am 28. Okto- ber 1967 in Salzburg eine Aussprache iiber
rheologische Probleme der Geomechanik statt, welche von der
Abteilung Felsmechanik am Institut fUr Bodenmechanik und
Felsmechanik der Universitat Karlsruhe gemeinsam mit der
Osterreichischen Gesell- schaft fUr Geomechanik veranstaltet wurde.
An die einleitenden Vortrage schloB sich eine lebendige Wechselrede
an, welche so viele und interessante Kontakte zwischen den von den
einzelnen Teilnehmern vertretenen Arbeitsgebieten anspringen lieB,
daB es den Herausgebern wert er- schien, die ganze Aussprache, zwar
in konzentrierter Form, im wesentlichen aber doch vollstandig,
wiederzugeben. Fiir die umsichtige Mitarbeit bei der Vorbereitung
und DurchfUhrung des Kol- loquiums sowie bei der Redigierung der
Diskussionsbeitrage gebiihrt Herrn Dipl. -Ing. H 0 fm ann,
Karlsruhe, besonderer Dank. Leopold M ii 11 e r-Salzburg
Inhaltsverzeichnis Einleitende Vortriige Leipholz, H. : Grundlagen
der Rheologie ...Langer, M. : Grundbegriffe der Rheologie und ihre
Anwendbarkeit bei der Verformung von Gebirgskorpern ...9 Zisminsky,
U. : Rheologie und Felsmechanik aus geologischer Sicht ...2L
Korner, H. : Kinematische Betrachtungen zum Rankineschen
Spannungszustand in der geneigten, kriechenden Schicht ...33
AU88prache 1. Begriffe 55 Elastisch - plastisch - viskos - FlieBen
- Kriemen II. Kin e mat i s c h e K r i e c h the 0 r i e ...64
Frage der Standsimerheit - Probleme des Stoffgesetzes und der
Bruchbedingungen III. Probleme des GroBenbereiches ...70 Kontinuum
- Diskontinuum - Bestimmung von Gesteins- und Gebirgsparametern
Felsmechanik u. Ingenieurgeol. , Suppl. V.
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