Step-Like and Chaotic Behavior of Pore Pressures in Clay during Loading

摘要

Measurements made with vibrating wire piezometers of the rates of change of pore pressures in a clay aquitard during loading revealed a complex behavior over short time periods. Pore pressure velocities were found to progress in evenly-spaced steps rather than in a smoothly continuous manner. This was duplicated in a numerical poroelastic model and is a result of the strong coupling of strains and pore pressures. Pore pressure velocities in the field data were found to exhibit deterministically chaotic behavior in the form of a strange attractor, whose basic shape was duplicated by the model. The velocity histories demonstrate a fractal nature as they repeat when the data is examined on a finer scale. For poroelastic systems, attractor construction offers a supplemental means to verify mathematically correct modeling and may be useful for field studies.