University of Minnesota

Ioannis G Vardoulakis

Andrzej Drescher

Joseph F Labuz

Euripides Papamichos

A compression test apparatus for geomaterial, such as rock or concrete, samples that is designed to provide measurements of a stress displacement characteristics of the failure zone. A geomaterial formed into a specimen comprising a right rectangular prism is supported by walls along two parallel faces and a back face. An axial load is kinematically applied by a plate that is suitably guided for movement against the specimen which is supported on bottom support plate. All of the surfaces in contact with the specimen are lined with hardened and polished steel plates and lubricated to minimize friction. The assembly of the specimen and its supports is in a conventional loading frame so that an axial load can be applied to one end of the specimen and reacted against the bottom plate. Displacement transducers monitor the lateral displacement of an unrestrained side surface of the specimen.

Surface instability detection apparatus

A bi-axial compression test apparatus for geomaterial (soil, etc.) samples that is designed to allow free shear band formation and provide measurements of the stress displacement characteristics of the failure zone. A geomaterial sample formed into a specimen comprising a right rectangular prism is surrounded by a thin rubber membrane and is supported by walls along two parallel faces. An axial load is kinematically applied by a plate that is guided to prevent any tilt or eccentricity, while a bottom support plate for the specimen is horizontally guided by a linear bearing that is substantially friction free. All of the surfaces in contact with the specimen are glass lined and lubricated to minimize friction. The assembly of the specimen and its supports is placed in a conventional tri-axial cell in a loading frame so that an axial load can be applied to one end of the specimen and reacted against the bottom plate. Internal loaded load cells allow for accurate measurement of the axial force, and any eccentricities thereof, as well as friction along the side walls. Displacement transducers monitor the axial and lateral displacements of the specimen and the horizontal movement of the bottom plate, to permit analysis of the shear mode, and when to determine shear failure occurs.

Growing community of inventors

Minneapolis, MN, United States of America

Ioannis G Vardoulakis