INTERPRETATION OF MODEL PRESSUREMETER TEST USING AUTOMATED CLAY CALIBRATION CHAMBER DATA

The details of an automated flexible wall calibration chamber test sys tem developed to perform strain-controlled model pressuremeter testing in cohesive soil are presented. The procedure involved in obtaining u niform specimens by consolidating a slurry of kaolin in two stages is described. The importance of automated control (electro-pneumatic cont rol for this study) to perform second stage K-0 consolidation accurate ly is shown. Typical test results are presented along with the evaluat ion of undrained strength, initial shear modulus, stress-strain variat ion, limit pressure, and horizontal stress using various methods of in terpretation. Unload-reload loops were performed, and the shear modulu s values were compared with the deduced values from the initial loadin g curve. Interpreting the pressuremeter test data using the Marquardt- Levenburg algorithm is presented. The improvements to the Simplex meth od are identified along with the effect of the reference state. A new procedure for incorporating the unloading portion in interpreting the pressuremeter test data is developed along with the detailed compariso ns.