ABSTRACT
The paper describes a new approach for the back-analysis of laboratory tests using the Particle Flow Code (PFC). The theoretical background is explained in detail including some major new developments like the incorporation of hydromechanical coupling. The hydromechanical coupling allows investigation of the hydraulic regime inside the specimen, such as porewater pressure development and internal flow. Our investigations indicate that, during progressive damage, the micromechanical porewater pressure distribution is highly inhomogeneous.
The practical use of the method is shown in the form of a back-analysis of a series of triaxial laboratory tests on Opalinus Clay for the Mont Terri Project (international project under the patronage of the Swiss National Hydrological and Geological Survey).
Both, the macromechanical behavior, in the form of stress-strain curves, and the micromechanical behavior, in the form of the internal damage of the sample have been reproduced. The approach allows a distinction between the micromechanical shear and tensile cracks. Progressive damage leads to macroscopic cracks and to the formation of shear bands. The practical application also demonstrates that the Particle Flow Code is able to reproduce the pre- and post-failure behavior of the sample.
