University of Minnesota

Ioannis G Vardoulakis

Andrew Drescher

Joseph F Labuz

A plane-strain apparatus is provided for testing soft rock and concrete specimens for failure under compression load in a direction generally along a central axis of the specimen. The specimen has first and second end surfaces, and four side surfaces, which form a generally rectangular prism cross-section configuration. The apparatus includes a bottom support plate supporting the first end surface, and a top plate for loading the second end surface. A frame surrounds the specimen and supports a pair of diametrically opposite base wedge plates aligned with two opposite side surfaces of the specimen. The frame is spaced from the specimen and the base wedges and mating adjustable wedge plates which engage the opposite surfaces of the specimen facing the base wedge plates. The cylindrical frame, and the base wedges and mating adjustment wedge plates restrain movement of the opposite side surfaces of the specimen to be tested in first lateral directions perpendicular to the axis of loading. The specimen is substantially unrestrained from shifting in directions parallel to the adjustable wedge plates. A mechanism for loading the specimen is provided at the second end surface. The applied load is directed by the top plate toward the support plate until the specimen fails in shear and at least two portions of such specimen shifts in a direction parallel to the side plates. Low friction linear slide mechanism is provided for mounting the top plate for movement along a linear support substantially parallel to the plates of the wedges.

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Athens, Greece

Ioannis G Vardoulakis