Membrane filter properties and application of the filter to undrained cyclic triaxial test of unsaturated materials
Properties of the membrane filter recently introduced as an alternative to the ceramic disk are revealed through diffusion and hydraulic conductivity tests. It is shown that diffusion of air through the membrane filter is significantly affected by suction magnitude and that hydraulic conductivity of the membrane filter can easily be affected by the quality of water used in the test. The application of the membrane filter to the soil-water characteristic curve tests (SWCC tests) shows that similar SWCCs can be obtained by employing pressure plate apparatuses with either the ceramic disks or the membrane filter installed, and that repeatability of the SWCC by using the membrane filter pressure plate apparatus is reasonably good. The application of the membrane filter to the undrained cyclic loading test of unsaturated sandy materials shows that the response (the duration to measure the equilibrated pore-water pressure of unsaturated materials) of the membrane filter pedestal in a modified triaxial system may be as short as ∼2 s in certain test conditions, and fairly good pore-water pressure and air pressure measurements can be obtained during undrained cyclic loading with a loading frequency of 0.1 Hz.