LOW STRAIN SHEAR MEASUREMENTS OF SOFT SEDIMENTS USING TRIAXIAL VANE DEVICE (TRIAXIAL VANE TESTING, SOFT CLAYS)

A new semi-computer aided testing procedure was designed and implemented to determine low shear strain properties of soft saturated clays. Components of the test set-up were a triaxial vane device, data acquisition units to detect small strain amplitudes, and a microcomputer. Real-time data acquisition and interactive computer graphics were utilized to collect and analyze data. The average range of electronically measured strain amplitude was from 10('-4)% to 1%. Approximately 1500 data points were taken in this range. Testing could be extended to determine undrained shear strength of the specimens, occurring between 10% to 20% of shear strain amplitude, and beyond for residual strength measurements.; Using duplicate specimens, shear moduli reduction curves were obtained through resonant column testing and the new triaxial vane shear testing procedure and they were compared. The dynamically determined low strain shear stress-strain behaviour was found to be substantially influenced due to cyclic degradation for the soft saturated clay specimens. Whereas, static testing using the new procedure resulted in acquisition of better quality and more realistic low shear strain data for these types of soils. For normally consolidated specimens, Gmax-static/Su was found to be 112, and Gmax-static/Gmax-dynamic was 0.85.