Development of a Stress/Suction-Controlled True Triaxial Testing Device for Unsaturated Soils
Hoyos LR, Macari EJ
(Received 14 June 1999; accepted 11 July 2000)

Abstract
A servo-controlled, true triaxial (cubical) testing apparatus has been modified to test 10-cm cubical specimens of unsaturated soil under suction-controlled conditions and for a wide range of stress paths. The equipment is a mixed-boundary type of device, with the specimen seated on top of a saturated high-air-entry disk and between five flexible membranes on the remaining sides of the cube. This paper describes the development of the device, including details of main apparatus components, specimen preparation, step-by-step assembling procedure, and the corresponding validation of its suitability for testing unsaturated soils. The device features two independent pore-air pressure and pore-water pressure control/monitoring systems. Matric suction states in the specimens are induced and maintained constant during testing by using the axis-translation technique. A companion paper (Macari and Hoyos Jr. 2001) presents the results from a comprehensive experimental study of the stress-strain response of a recompacted silty sand following simple-to-complex stress paths under suction-controlled conditions.

Keywords:
axis-translation technique, high-air-entry disk, matric suction, multiaxial stress state, pore-air pressure, pore-water pressure, soil, triaxial, ture triaxial apparatus, unsaturated soils

Paper ID: GTJ2410005

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Author Hoyos LR, Macari EJ Title Development of a Stress/Suction-Controlled True Triaxial Testing Device for Unsaturated Soils Symposium , Committee on