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

通过2004年至2006.1年度的研究活动，取得了以下成果。走滑断裂系统的野外考察在三浦半岛的野外考察表明，岩体中的走滑断裂系统由Riedel剪切和P-剪切组成，形成花状构造。天然岩石在刚性加载机上的围压断层模型试验川崎凝灰岩岩板的加载试验表明，岩板的表面断裂带由里德尔剪切、P剪切和白化破碎带组成。在高围压作用下，裂隙带伸展受到收缩，但裂隙带大小随断层位移的增大而增大。走滑断层系统的模拟实验在人造岩石中，沿着基底断层进行走滑位移的实验，得出走滑断裂带。目的是利用X射线CT扫描仪，从三维上研究组成断裂带的构造单元的几何形状和发育顺序。在基底位移增加的情况下，人造岩石的变形表现为：1)在人造岩石表面观察到与Riedel剪切和P-剪切相对应的层状断裂。2)新的剪切(外剪切)从Riedel剪切和P剪切的交汇点开始，并沿着由Riedel剪切和P剪切组成的断裂带传播。在垂直剖面上，这些剪切力从基底断层(花状构造)或接近人造岩石顶面的分支(“Y”形构造)发散。对走滑断层诱发岩层变形破坏机制的统一认识通过上述野外调查和两种类型的断层模型试验，对岩层地表和岩层断面的变形破坏机制有了统一的认识。

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.