The anisotropy of Leighton Buzzard sand under general stress conditions
A hollow cylinder apparatus was used to investigate the inherent anisotropy and membrane penetration of Leighton Buzzard sand test-specimens. The degree of inherent anisotropy was found to be independent of the mean effective stress but dependent on the initial relative density of the test-specimen. In the vertical-tohorizontal directions, the degree of inherent anisotropy decreases with increasing relative density. A wet-pluviation, sample preparation technique produces cross-anisotropic test-specimens, with the degree of cross anisotropy independent of the initial relative density. The effects of membrane penetration (expressed in terms of the normalized unit membrane penetration) are found to be independent of the initial relative density and the mean effective stress.
Truly undrained response of granular soils with no membrane-penetration effects
Conventional and truly undrained behaviour of granular soils is compared by direct experimental measurements. The truly undrained behaviour was determined by compensation for membrane penetration i...
Volume Changes During Undrained Triaxial Tests on Saturated Dilatant Granular Materials
Synopsis The results from a set of simulated undrained tests on saturated samples of lead shot, in which the volume of the pore-water is maintained constant for part or all of the test by increasing the cell pressure, are shown to be very similar to those obtained from undrained tests. They are used to show that considerable volume expansion of the sample may occur during an undrained test in which cavitation does not occur, and that this expansion is balanced by penetration of the rubber membrane into the sample under the increasing effective stress. From a further set of tests, it is concluded that if the same sample dimensions and rubber membranes as those herein are used, the error in the “cohesion” corresponding to the φu = 0 condition (Bishop and Eldin, 1950)1 is likely to be small for materials finer than coarse sand. Further, this error may be reduced by employing thicker membranes and samples of larger dimensions. The fact that the tangent to the Mohr circles from the undrained tests intercepts t...