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Abstract: In order to assess the influence of remote mean stress correlated with depth of burial on the principal mode of failure at fault tips during fault slip in a lithologically homogeneous, fractured rock mass, the growth mechanisms of strike-slip faults have been studied at outcrop-scale in the siliceous mudstones of northern Hokkaido, Japan. We take a multifaceted approach combining i) geological characterization of fractures by fracture mapping in outcrop and fracture logging of boreholes (drilling depth: ≤1020m), ii) rock mechanical characterization by laboratory tests on core samples, and iii) theoretical analyses using the Griffith–Coulomb criterion. These suggested that the principal mode of failure in the mudstones is dependent, not only on rock strength, but also on remote mean stresses. During and/or after uplift and erosion the faults grew mainly by linking with adjacent faults via numerous splay cracks, formed by tensile failure above roughly 400m depth. In contrast, below this depth, the faults grew predominantly by shear failure. Such growth mechanisms are consistent with the fact that hydraulic tests performed in boreholes show that highly permeable sections (hydraulic transmissivity: >10−5 m2/s) are restricted to depths of less than 400m. [ABSTRACT FROM AUTHOR]

• Non-contact strain evaluation by DIC using speckle patterns of surface flaws was applied and reliability of the technique was demonstrated. • Room temperature tensile behavior of Japanese RAFM, F82H, irradiated to ∼70 dpa at 573 K was preliminarily evaluated. • No possible irradiation-induced change of the elastic properties in both axial and transverse directions for irradiated F82H was demonstrated. The small specimen tensile test is commonly used as the basic test to evaluate the irradiation effect on the strength of fusion structural materials after irradiation, and a lot of attempts were made to qualify the data obtained by small size specimen, but the specific attention on the evaluation of strain were not satisfactory given. This study therefore aims to propose a novel non-contact strain measurement technique, based on digital image correlation (DIC) method, for reduced-activation ferritic/martensitic (RAFM) steel, e.g., F82H, as the leading candidate structural material of fusion in-vessel components in Japan. A flat rectangular miniature specimen, e.g., SS-J3 type, was adopted to evaluate non-irradiated and neutron-irradiated tensile properties. In the proposed DIC, very tiny surface machining flaws were recognized by the DIC computation program and utilized to set several pairs of the gauge end points with a fixed gauge length. In case of the room-temperature test, it was clearly demonstrated that this procedure could provide more precise and reliable data compared with the previous approach of the single-scan measurement under floated gauge length. Superior linearity was achieved and recognized DIC points of concern were traceable during the entire period of the test. By applying this technique, superior high-dose stability of elastic properties of F82H was first demonstrated. [ABSTRACT FROM AUTHOR]