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US 4,825,700 AGranted
Bi-axial geomaterial test system
AssigneeRegents of the University of Minnesota
InventorsIoannis G. Vardoulakis, Andrzej Drescher
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AssigneeRegents of the University of Minnesota
InventorsIoannis G. Vardoulakis, Andrzej Drescher
Estimating the term…
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.
In a bi-axial test apparatus for testing geomaterial samples for failure under load in direction generally along a central axis of the specimen, for a specimen with top and bottom end surfaces, and four side surfaces, forming a generally rectilinear cross section configuration, comprising a bottom support plate supporting a bottom end surface of said specimen, a pair of side plates at two opposite side surfaces of the specimen for restraining movement of the specimen in first lateral directions perpendicular to the axis, the specimen being loaded being substantially unrestrained from shifting in direction parallel to the side plates, means to load such specimen on a top end surface under a load directed toward the bottom support plate axially along such specimen until the specimen fails in shear and at least two portions of such specimen shift in a direction parallel to the side plates, the improvement comprising glass surfaces on the side plates for engaging a specimen to be tested.
A bi-axial test apparatus for testing geomaterial sample specimens for failure under load in direction generally along a central axis of the specimen, which has first and second end surfaces, and a pair of generally parallel side surfaces, comprising a support plate supporting a first end surface of said specimen, a pair of side plates fixedly mounted relative to the bottom support plate for restraining movement of the parallel side surfaces of a specimen to be tested in a first lateral direction perpendicular to the axis of loading the specimen being tested being substantially unrestrained from shifting in directions parallel to the side plates, means for loading such specimen on a second end surface under a load directed toward the support plate along the central axis of the specimen until such specimen fails, and means for supporting the support plate for movement relative to the means for loading along a support axis parallel to the parallel surfaces of such specimen and perpendicular to the loading direction comprising a ball bearing supported slide member that provides friction free movement of the support plate relative to the means for loading.
A bi-axial test apparatus for testing a geomaterial specimen for failure under load in direction generally along a central axis of such specimen comprising a bottom support plate supporting a bottom end surface of such specimen, a pair of side plates at two opposite side surfaces of the specimen for restraining movement of the specimen in first lateral directions perpendicular to the central axis, the specimen being loaded being substantially unrestrained from shifting in directions parallel to the side plates, means to load such specimen on a top end surface under a load directed toward the bottom support plate in direction of the central axis of such specimen until the specimen fails in shear, and a plurality of load cells supported on the apparatus for measuring the load on a specimen transferred to the bottom support plate, said load cells being arranged at a know relationship to, but spaced from the central axis to indicate eccentricity of the center of loading relative to the central axis.
Dependencies are inferred from the claim text.