Volume 35, Issue 3 (May 2012)
Technique for Undrained Triaxial Tests on Unsaturated Soils Using Active Control of Pore-Air Pressure
Triaxial testing apparatus and procedures for unsaturated soils have become common along with the development of equipment and sensors. Although many drainage conditions are related to the pore-air and pore-water phase, the drained pore-air condition is usually adopted for tests of unsaturated soils. The main reason is that it is difficult to keep the pore-air undrained because the air diffuses easily through a rubber membrane. However, pore-air and pore-water are sometimes not allowed to drain under ground deformation problems. Therefore, undrained conditions in which pore-air and pore-water are not allowed to flow in and out of the soil are achieved in the experiments described herein. First, problems of a conventional triaxial apparatus for unsaturated soils were investigated to produce the undrained conditions. Then, triaxial testing methods under the undrained conditions were developed for overcoming the problems. Finally, the performance of the proposed testing procedure was demonstrated in comparison with results obtained using conventional testing.