A system for controlled suction in triaxial tests

Vapour Equilibrium and Osmotic Technique for Suction Control

“…When the drying air was shut off, specimens were allowed to equilibrate so some hysteresis in specimens would be expected before reaching equilibrium. Blatz and Graham (2000) used a closed system with a target suction applied in a glass desiccator connected with a sealed circulation system. Figure 10 shows a schematic of the apparatus.…”

“…The graduated capillary tube inserted into the reservoir is used for monitoring water exchanges. In order to ensure a constant pore air pressure equal Triaxial apparatus with VET suction control (after Blatz and Graham 2000) to the atmospheric pressure within the sample, an air vent was machined on the base of the cell. This vent is connected with an antievaporation system to neutralize water evaporation from the sample.…”

Recent developments in the techniques of controlling and measuring suction in unsaturated soils

“…The main drawback of this experimental setup is that the time to reach moisture equalisation is extremely long due to the fact that vapour transfer depends on diffusion (several weeks are required for each suction step in the case of high-density clays as observed in Figure 7). In order to speed up the process, vapour transferthrough the sample or along the boundaries of the sample-can be forced by a convection circuit driven by an air pump (Yahia-Aissa 1999, Blatz and Graham 2000, Pintado 2002, Lloret et al 2003, Oldecop and Alonso 2004, Dueck 2004.…”

Geoenvironmental Testing

“…For this reason, many researchers adopted the technique of controlling suction by vapour control (see for instance Delage et al 1998a). Following Esteban Moratilla (1990) and Oteo-Mazo et al (1996), the technique has also been adapted on various geotechnical devices such as oedometer or isotropic compression equipments (Yahia-Aissa et al 2000;Tang and Cui 2006;Hoffmann et al 2005) or triaxial apparatuses (Blatz and Graham 2000). Figure 4 (Delage et al 1998a;Yahia-Aissa et al 2000) shows the water retention curves of compacted FoCa7 clay determined by using both the vapour control technique and the osmotic technique.…”