Volume 21, Issue 1 (March 1998)
Interpretation of Model Pressuremeter Test Using Automated Clay Calibration Chamber Data
The details of an automated flexible wall calibration chamber test system developed to perform strain-controlled model pressuremeter testing in cohesive soil are presented. The procedure involved in obtaining uniform speciments by consolidating a slurry of kaolin in two stages is described. The importance of automated control (electro-pneumatic control for this study) to perform second stage K0 consolidation accurately is shown. Typical test results are presented along with the evaluation of undrained strength, initial shear modulus, stress-strain variation, limit pressure, and horizontal stress using various methods of interpretation. Unload-reload loops were performed, and the shear modulus values were compared with the deduced values from the initial loading curve. Interpreting the pressuremeter test data using the Marquardt-Levenburg algorithm is presented. The improvements to the Simplex method 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 comparisons.