Anisotropic hardening of an initially isotropic porous limestone
Celle, Cesare Cafferata
Cheatham, John B.
Master of Science
The lack of a good description of the behavior of a compacting material that exhibits yield-strength dependence upon hydrostatic pressure, prompted the present study to determine experimentally a yield envelope that would predict the material behavior more accurately. True triaxial tests were performed on Cordova Limestone in order to find detailed information about the stressstrain behavior of this material. From the results of these tests a yield surface was obtained and the experimental data showed normality to be a very good approximation for the actual plastic strains produced by the initial yielding of the material studied. Subsequent yield surfaces were obtained experimentally and it was found that the yield surface displaces in the stress space as hardening takes place. Different tests were performed in order to obtain the shape of the low hydrostatic stress region of the yield envelope. Induced anisotropy due to hardening led to a closing of this yield envelope and a kinematic hardening rule completed the description of the limestone's plastic behavior. The consistency between the predicted and observed stress-strain behavior indicates that the proposed yield envelope model and a kinematic hardening rule correspond to a proper description of the behavior of this limestone.