Three-dimensional deformation and failure mechanism of surrounding rock ground induced by strike slip fault displacement

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The following results were obtained through research activities from 2004 to 2006.1. Field surveys of strike-slip fault systemsField surveys at the Miura Peninsula revealed that the strike-slip fault systems in rock mass consist of Riedel shears and P-shears forming flower structures.2. Fault model test under confining pressure using natural rock in an stiff loading machineLoading tests on rock plates made from Kawazu tuff showed that the surface fracture zones of the plates consist of Riedel shear, P shear and whitened crashed zone. The size of the fracture zone becomes large as the fault displacement increases, though the extension of the fracture zone is constricted under high confining pressure.3. Analogue Experiments of strike-slip fault systemsStrike-slip fault zones are induced experimentally in artificial rock subjected to strike-slip displacement along basement fault. The purpose is to investigate in three dimensions, the geometries and sequence of development of structural elements comprising the fault zones by use of an X-ray CT scanner. The deformation of the artificial rocks under increasing basement displacement was observed as follows.1) En echelon fractures corresponding to the Riedel shears and P-shears are observed at the surface of the artificial rock. 2) New shears (outer shear) initiate from the points of interconnection of Riedel and P-shears, and propagate aside from the fault zone that consists of Riedel and P-shears. In vertical cross section, these shears diverge from the basement fault (flower structure) or branch near the top surface of the artificial rock (`Y' shape structure).4. Unified recognitions on deformation and failure mechanism of rock ground induced by strike-slip faultThrough the above-mentioned field survey and two-types of the fault model tests, an unified recognition were obtained on the deformation and failure mechanism at the ground surface and at the cross section of the rock ground induced by the strike-slip fault.