This review highlights the contribution of Oda et al.'s works in offering a new perspective on the depth-dependent permeability of discontinuous rock masses. By integrating Oda's permeability tensor theory with the fracture closure model proposed by Bianchi and Snow, they derived a closed-form expression for a stress-dependent permeability tensor. The formulation is practically applicable, as all parameters can be determined directly from conventional field survey data. The validity of the model has been verified through comparisons with in-situ measurements conducted in Japan, Sweden, the United States, and Canada. This approach offers a valuable framework for designing site investigations in future and for the preliminary interpretation of field results. To support this understanding, the present paper reviews a series of studies by Oda et al. concerning the theoretical development and engineering application of stress-dependent permeability models for discontinuous rock masses.

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This article is a summary of the paper published in “Engineering Geology” (Scibek et al., 2025). In this study, we reviewed common practices for conducting gas probe-type permeameter pressure-decay tests and steady-state gas flow tests on unconfined rock samples. The development of this permeameter tool took over 5 years, and it was related to testing new rapid test methods on drill cores from faulted and undeformed granites at the former Mizunami research site (JNC, 2003) in Gifu Prefecture, with the kind support of JAEA staff and the provision of drill cores from the Shobasama drill site on the Tsukiyoshi Fault (JNC, 2005). The paper in the Engineering Geology journal presents a description of the methods, with examples from a wide selection of granitic drill core samples of the Toki Granite (Mizunami site), with additional low-permeability samples of cut Inada Granite (Ibaraki Prefecture), and highly permeable artificial porous ceramic materials.

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It is essential, in a mountain tunnel construction project, to mitigate geological and geotechnical uncertainties through the acquisition of ground information ahead of the tunnel face is essential for the improvement of construction safety and the rationalization of construction costs and schedule. Therefore, displacement monitoring methods are often adopted to identify changes in rock mass conditions ahead of the tunnel face and assess the necessity for auxiliary measures. Developed here were monitoring methods for 3D ground deformation (vertical and horizontal along the face advance direction, and the tunnel lateral displacement) ahead of the face, called “TN-Monitor^®” in which all measurement instruments can be installed from inside the tunnel. This measurement technique is so groundbreaking that it can contribute to further applicability expansion of tunnelling methods in severe construction conditions, such as tunnelling in built-up areas with surrounding structures and tunnelling with large overburden. This article comprehensively describes a series of development of the TN-Monitor and summarizes some technical papers (Sakai et al., 2016 and Sakai et al., 2023).

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