| Popis: |
Today, it is well known that most geotechnical infrastructure resting on or made of unsaturated soils experience a wide range of deformations. Calculation of foundation settlement, for instance, requires a good estimation of soil stiffness at relatively small strains. Analyses of slopes, embankments, and soil bearing capacity, on the other hand, require adequate estimation of shear strength, from peak to residual. To date, there is limited experimental evidence of unsaturated soil response at mid-to-large strain levels corresponding to residual shear strength, and virtually no research work is available that spans the whole range of deformations in unsaturated soils using ring shear testing technique under controlled-suction states. This paper introduces a novel ring shear apparatus suitable for testing unsaturated soil samples over a whole range of deformations via axis-translation technique. The lower annular platen features a full set of 5-bar ceramics for control of pore-water pressure during constant-suction RS testing. The paper outlines the full development of the apparatus, including details of its main components and the test procedures. Results from a preliminary series of suction-controlled ring shear tests on compacted silty sand are presented. |
