25. Caisson Foundations Subjected to Seismic Faulting: Reduced-Scale Physical Modeling

As part of the SERIES project, a number of physical model tests were conducted in the Laboratory of Soil Mechanics, National Technical University of Athens, to investigate fault rupture propagation through sand and its interaction with caisson foundations. Both normal and reverse faulting was simulated parametrically by varying the position of the caisson relative to the emerging fault rupture. The displacements and rotation of the foundation, as well as the deformation of the soil mass were recorded through image analysis and laser scanning of the ground surface. In the first case, high-resolution digital cameras were utilized to capture images of the deformed soil, which were then processed through image analysis. In the latter case, a novel technique was developed and applied through a custom system, designed and constructed inhouse. After each displacement increment the ground surface was scanned with 8 laser displacement transducers, travelling along the specimen at constant speed, producing a digital relief of the deformed surface. The caisson is shown to act as a kinematic constraint, substantially altering the rupture path. Its horizontal and vertical movement and rotation are a function of its position relative to the fault rupture. Depending on the latter, a variety of interaction mechanisms develop, such as bifurcation of the rupture path and diffusion of plastic deformation.