Some problems in triaxial test on saturated sands

Steady state (SS) strength, an important parameter in evaluating the stability of sand deposits against flow sliding, may be significantly affected by testing details including volume change during saturation and undrained shear, end restraint and non uniform deformation. The error in SS strength due to the volume change can be corrected by using a radial deformation transducer (e.g. HRDT) to measure the radial deformation of a triaxial sample. The effect of end restraint is insignificant for loose sand samples and can be considerably reduced by applying lubricated end platen. The thickness of the lubricant and the membrane should not be too thick to produce additional error in void ratio. A new method is suggested to correct the cross sectional area of a triaxial sample. Reuse of sheared sand material may produce large error in SS strength for sands with high coefficient of uniformity (C u ). The scatter of the void ratio in steady state is about 0.02 for sands with low value of C u , and can be over 0.06 for C u  of 2.0～2.7.