| Popis: |
In the direct measurement of soil matric suction cavitation, as a failure of water in tension, is an inevitable phenomenon that restrains HCTs in terms of the upper limit of measurable negative pore pressure and the sustainable measurement duration. After Imperial College’s pioneer design, researchers have been trying to deal with cavitation by improvements in not only design of the apparatus but also saturation procedures. The capacity of the tensiometer increases with the degree of saturation of the porous stone and the water reservoir of the device. Despite the variety of saturation methodologies in practice, a complete saturation can never be attained as some micro bubbles always remain in the system. A new saturation method, based on the substitution of air bubbles with CO2 gas was tested on UNINA probe. CO2 gas was used due to its physical and chemical advantages, namely its solubility and ionization potential in water. Time response tests during saturation showed that proposed method is able to achieve higher levels of saturation than the same procedure without CO2. Free evaporation and cyclic evaporation tests show noticeable improvement on maximum sustainable matric suction value. Moreover, experimental measurements give quite satisfactory results for long term measurement of the device even at its upper suction limit. |
