A research program on the shear behaviour of filled discontinuities was initiated jointly by the Polytechnic of Turin and the ENEL-DSR-CRIS of Milan. The relevant steps of this research program are described in the present paper, with emphasis being placed on: a) the design and construction of a special shear testing equipment, developed so as to simulate the failure behaviour of natural joints; b) the performing of a number of shear tests on both artificial and natural discontinuities. The following influencing factors are considered: different infilling materials of varying thickness; various surface profiles (roughness and asperities); different rock types (Limestone and Sandstone). After a detailed characterization of the unfilled discontinuities and of the infilling materials, the most attention is devoted to the study and the interpretation of the first shear tests performed on filled joints.
Un programme de recherche sur le comportement au cisaillement de discontinuites remplies a ete commence par l'ENEL-DSR-CRIS de Milan conjointement avec l'Ecole Polytechnique de Turin. Dans ce memoire on decrit les phases les plus importantes de ce programme de recherche, en mettant en evidence particulièrement les points suivants:
l'etude de projet et la construction d'un appareillage special d'essai au cisaillement, developpe pour simuler la comportement à la rupture de joints naturels;
l'execution d'un certain nombre d'essais de cisaillement sur les discontinuites soit naturelles soit artificielles, en prenant en consideration les facteurs d'influence suivants: differents materiaux de remplissage d'epaisseur variee; profils de surface differents (rugosites et asperites); divers types de roche (Calcaire et Gres).
Apres une caracterisation detaillee des discontinuites vides et des materiaux memes de remplissage, la plus grande attention a ete consacree jusqu'a present à l'etude et à l'interpretation des premiers essais de cisaillement effectues sur des joints remplis.
Das Polytechnlkum von Turin und die ENEL-DSR-CRIS von Mailand haben gemeinsam ein Forschungsprogramm ueber das Scherbedingung von ausgefuellten Trennungsfugen eingeleitet. Die wichtigsten Schritte dieses Forschungsprogramms sind in diesem Artikel beschrieben, wobei die folgenden Punkte hervorgehoben werden: a) Entwurf und Konstruktion einer Spezialausruestung fuer den Scherversuchen, die so entwickelt ist, daβ sie die Bruchbedingung von natuerlichen Fugen nachahmen kann; b) die Ausfuehrung einer Reihe von Scherversucben sowohl an kuenstlichen als auch an natuerlichen Trennungsfugen bzw. Unstetigkeitsstellen und zwar unter einer gewissen Anzahl von Versuchsbedingungen, wobei die nachstehenden Einfluβfaktoren zu beruecksichtigen sind: verschiedene Fuellmaterialien mit variierender Dicke; unterschiedliche Oberflachenprofile (Rauhigkeit und Unebenheiten); verschiedene Gesteinstypen (Kalstein und Sandstein). Nach einer gruendlichen Pruefung der Eigenschaften von nicht gefuellten Trennungsfugen und den Fuellmaterialien selbst haben die Studie und die Auswertung der ersten Scherversuchen an ausgefuellten Fugen bis heute die gröβte Aufmerksamkeit auf sich gelenkt.
The presence of discontinuities in a rock mass is known to influence greatly strength and deformability. As a consequence, the characterization of natural discontinuities is a very relevant step in rock engineering design of slopes and foundations. A significant aspect of characterizing rock joints relates to the infilling material and to the assessment of its influence on shear behaviour. The presence of filled discontinuities is a peculiar characteristic of "Complex Rock Formations" (A.G.I., 1977), which are often met during excavation workings in Italy. With the main purpose to increase the present knowledge on the subject, the Polytechnic of Turin and the Hydraulic and Structural Research Centre of the Italian Electricity Board of Milan (ENEL-CRIS) are involved in a joint research program on the shear behaviour of filled discontinuities (Barla et al, 1986). Given the complexity and the extent of this research program, the work has been subdivided in a number of steps as follows:
design and construction of the shear equipment (i.e. the shear box used for testing filled discontinuities);
choice of typical filled discontinuities;
preparation of artificial discontinuities, with various roughness profiles;
physical and mechanical characterization of the rock material, discontinuity, infilling;
set up and calibration of the shear equipment; choice of the most appropriate testing procedures to be used;
performance of the shear tests on artificially filled joints; g) performance of the shear tests on naturally filled joints;
analysis and interpretation of experimental data.
The shear tests on both artificial and natural discontinuities consider the following influencing factors:
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different infilling thickness;
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various surface asperities);
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different rock types; for two typical conditions which are usually met in situ:
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infilling material, in a joint within a porous rock (Sandstone), drained during the consolidation phase, and drained or undrained during the shear displacement;
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infilling material, in a joint within a nearly impervious rock (Micritic Limestone), drained radially during consolidation, and drained or undrained during shearing.
