LABORATORY PRESSUREMETER EXPERIMENTS IN CLAY SOILS

AN-BIN HUANG, Purdue University

Abstract

Previous experience from researchers and practitioners have generally concluded that the self-boring pressuremeter is potentially a very powerful tool for the determination of the stress-strain and strength parameters as well as horizontal consolidation characteristics for cohesive soils. However, this potential has been been realized in practice due to some drawbacks which include problems associated with strain rates, soil disturbance, and stress environment during a pressuremeter test. A calibration chamber system and testing procedures to perform chamber pressuremeter tests in cohesive soils were developed in this research. More than twenty model pressuremeter tests have been performed in the chamber. A method based on the Simplex curve fitting technique was developed to derive soil stress strain relationship from pressuremeter data. A stress controlled holding test procedure and its interpretation using a finite difference program were developed. One dimensionally (K(,o)) consolidated triaxial tests and oedometer tests were conducted to provide reference soil parameters. Results of the model pressuremeter tests show that the initial shear modulus as derived from the pressuremeter interpretation increases with strain rate and is very sensitive to stress disturbance. The peak principal stress difference decreases with strain rate; after reaching a minimum value, the peak stress difference then increases with the strain rate. As strain rate increases, the interpreted soil stress strain relationship becomes more strain softening. The stress disturbance affects the measurements of initial lateral earth pressure and initial shear modulus but has little impact on the latter part of the test. The limit pressure is relatively insensitive to strain rate and stress disturbance. The horizontal coefficient of consolidation (c(,h)) from stress controlled holding tests in normally consolidated samples are very close to those determined from horizontal oedometer tests under virgin loading.

Degree

Ph.D.

Subject Area

Geotechnology

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