Advanced laboratory testing to characterize stiff, geologically aged clays
Presenter: Prof. Richard Jardine
Title: Advanced laboratory testing to characterize stiff, geologically aged clays
Launching Date & Time: 1st of June 2015 12:00pm GMT
Advanced laboratory testing to characterize stiff, geologically aged clays
Session Question & Answer [CLOSED]
Peteris Skels
Dear Richard, We are now testing Glacial Till here in Latvia and facing several problems with UU triaxial test. Because Till when extracted from depth of about 30m is not fully saturated anymore. What would you suggest to obtain undrained shear strength!?!? It is not possible to test it in situ, because of gravel. We use 70mm diam. samples and trying not to test with gravel >1/10, e.g., 7mm. What is your experience on Glacial Till UU testing!?!?
Peteris Skels
P.S In case during the UU triaxial test Glacial Till does not follow ideal 'critical state' of fi=0, can we still assume that undrained shear strength value is valid!? The results are closer to what we see during CU triaxial test..
Richard Jardine
UU testing is generally less reliable than undertaking tests on samples reconsolidated to in-situ stresses, after full saturation. Samples that have been taken from well below the water table would generally only desaturate if they have large pore spaces and are coarse grained. Clays can usually hold enough suction to remain saturated. Laminated (clay-silt or clay-sand) samples can de-saturate within their coarser fractions and cause special problems.
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