A Large Permeameter for Study of Internal Stability in Cohesionless Soils
Moffat, RA
Assistant Professor, University of Chile, Santiago, Chile

Fannin, RJ
Professor, University of British Columbia, 6250 Applied Science Lane, Vancouver, B.C., V6T 1Z4, Canada

(Received 4 November 2005; accepted 24 February 2006)

Abstract

Results are reported from the commissioning of a large rigid-walled permeameter that was designed to examine hydromechanical conditions prevailing at the onset of seepage-induced failure in soils with a potential for internal instability. A technique of slurry mixing and discrete deposition is used to reconstitute a homogeneous, saturated test specimen. The test specimen is consolidated and then subject to seepage flow, under head-control, in either a downward or upward direction. Two arrays of pressure transducers, located on opposite sides of the specimen, establish the variation of hydraulic gradient along the specimen. The device is configured with a top and bottom load cell, and frictionless loading ram, in order to assess the influence of side-wall friction and thereby establish the distribution of vertical effective stress along the length of the specimen. Observations of hydraulic gradient and effective stress enable a characterization of the onset of instability, which is localized within the specimen. Results of multi-stage tests on glass beads are reported that illustrate novel features of the permeameter and instrumentation, the utility of the specimen reconstitution technique and a novel approach for quantifying the onset of internal instability.

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