Hi, we are testing the coefficient of permeability of a remoulded clay sample using AS 1289.6.7.3, flexible wall triaxial method. However, after saturation and consolidation perculation stage was done for more than 24 hours. However the flow rate is significantly different from initial to final stage and permeability is changing from 1x 10-7 m/s to 1x 10-9 m/s. I believe this could be due to particle clogging in filter papers. I am confused when it comes to decide the permeabiltity. What would be the most accurate stage for selection of flow rate from this attached flow vs time graph?
Effective cell pressure was 50 kPa and the hydraulic gradient was 15.
Dear Samanthi, it's an interesting topic! How many times this happen? Have you more information about the detail process you have done? Have you tried with other hydraulic gradient? I'm interested in this
Well, once the flow rate gives us a very good overview, that show that the permeability for such material is still good... But if the flow rate does not gives us a good overview then the interstitial of such material must have been affected over time. The permeability of clays differs based on the chemistry of such clay and clogging effect plus the electric charge of that clay. What type of caly are you using for the experiment?
It is due to swelling of clayey soil, it is evident in the infiltration tests in black cotton soil.
10 ^-9 permeability value is consistent as order of magnitude with a clay. I believe that it is also correct to read the permeability over very long times, especially if it is determined in fine soils, i.e. after 24 hours ... the curve, in fact, tends asymptotically to that value.
An interesting paper on consolidation and desiccation of clay slurries
https://www.researchgate.net/publication/321844141_A_framework_for_coupled_consolidation-desiccation_behaviour_of_clay_slurries
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